HP 4274A LCR Meter - mini teardown - Page 1
Forum section: electronics / testgear

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 12:15:20 am
content: Hi,I have mentioned the HP 4274A LCR meter several times in my discussion of ESR Meters. I bought a second one today, so I thought I would share tips on buying this instrument and some pictures of the insides.This LCR meter was manufactured in the 80s, by a joint venture between Hewlett Packard and Yogogawa. So you will see a little different style than HP equipment of the same vintage.This is a high precision LCR meter 0.1% basic accuracy and 5 1/2 Digits of resolution. With option 001 or 002 you can measure capacitors with a dc bias voltage. The accuracy specifications are fairly complex. The accuracy becomes lower at high and very low impedances. I have attached a section from the Operators manual giving the accuracy.The particular unit that I have photographed was manufactured in 1987.Buying GuideIf you do a quick check on eBay you will see that most of the units are reporting Errors. This is quite normalbut can be used to your advantage to get a good price. The unit I am showing here I bought for $250.00If you plug a unit in with nothing connected, you will get a display like this:For it to work properly, the Lcur must be connected to Lpot, Hcur connected to Hpot and all four of the BNC shield connected together.Here is a picture of the same unit with my home made Kelvin leads attached:Also the Bias selector switch on the back should be set to OFF:Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 12:23:53 am
content: Hi,So let us have a look inside:You can see the power supply section and the card-cage assembly.This is a shot of the card-cage. The colour-coded ejector tabs are classic HP:This is the A1 Range resistor and Null Detector Assembly:With shields removed you can see some read relays and some high quality analog circuitry:Here is close-up of the relays:Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 12:35:06 am
content: Hi,More pictures of the 4274A.This is the A3 Power Amplifier Assembly, the circular black components are potted transformers:This board is called the A4 Process Amplifier Assembly:All these boards contain the Yogogawa Hewlett-Packard Logo:The microprocessor board contains a Lithium battery to save the front panel settings in NVRAM:Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 12:43:26 am
content: Hi,To get repeatable accurate readings, the HP4274A uses a kelvin test fixture. The Kelvin test fixture can cost as much as the LCR meter.Here is the 16047A installed on the 427A measure the Capacitance and ESR of small electrolytic:Here is a close-up of the test fixture:The inserts in the test fixture can be changed for radial and axial components:Jay_Diddy_B

author: rstoer
author_rank: Regular Contributor
timestamp: March 02, 2014, 01:04:30 am
content: Good information. Thanks.

author: Vgkid
author_rank: Super Contributor
timestamp: March 02, 2014, 01:08:44 am
content: Thanks for the teardown, where are the range resistors?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 01:23:51 am
content: Hi,The range resistors are on the A1 assembly. Here is a photograph:There are 5 covering 10, 100, 1K, 10K and 100K with dc and ac trims.The resistors are marked TKD, this the Yogogawa influence.Jay_Diddy_B

author: Vgkid
author_rank: Super Contributor
timestamp: March 02, 2014, 02:36:05 am
content: Im suprised to see that the resistors have a trim ability, i figured that it would have tbrown off the freq response.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 02:47:53 am
content: Hi,Here is the schematic from the manual:The trimmers have a +/- 1% adjustment range. The trimmer capacitor are marked 'phase'. This is to make them resistive.The 4274A is a 100 Hz to 100 kHz LCR meter. I also have the 4275A which covers the range 10kHz to 10 MHz. It would be interesting to see how different this section is for 10 MHz operation.Jay_Diddy_B

author: Vgkid
author_rank: Super Contributor
timestamp: March 02, 2014, 03:24:03 am
content: It would nice to see a comparison between the two models. Im surprised they didnt just use one precision thin film resistor for each range. Also those are massive units.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 03:44:15 am
content: Hi,One of the features of the 4274A is that you can adjust the test signal amplitude. The maximum current is 100mA. So this probably why there are some big resistors in the Range resistors.Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 04:00:47 am
content: There is an interesting article on the 4274A and 4275A in the HP Journal:http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1979-02.pdfJay_Diddy_B

author: dc101
author_rank: Regular Contributor
timestamp: March 02, 2014, 05:13:29 am
content: Nice pics man, looks in great shape. Do you know the reasoning behind the potted transformers? I've never seen them before. Is it similar to how they have transformers in oil?

author: Vgkid
author_rank: Super Contributor
timestamp: March 02, 2014, 05:23:07 am
content: Going by the app note they should be for dc blocking in the signal path.

author: casinada
author_rank: Frequent Contributor
timestamp: March 02, 2014, 07:50:22 am
content: Looks that those PCBs are pre silk screen days. All the labeling is etched on the PCB just like the circuit traces.I wonder who was the first to implement silk screens on the PCBs

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 11:18:28 am
content: Quote from: casinada on March 02, 2014, 07:50:22 amThis unit was described in the HP Journal in 1979. The schematics are definitely hand drawn. There is a high probability that these boards artworks were generated without a CAD system. I see some evidence of the boards being taped.Before CAD systems were used, the process of designing a board:1) The artwork was drawn with red and blue pencils. By tradition red was used for the solder side and blue was used for the component side.2) Pre-cut paper donuts were used for the pads. Bishop Graphics was one of the main suppliers of these pads. The pads were placed on a sheet of Mylar.3) A second sheet of Mylar was then placed on top. Red and Blue tapes were then run between the pads.4) This artwork was normally generated twice actual size.5) The artwork was then reduced to 1:1 with a process camera. Coloured filters were used to separate the top and bottom layers.6) The boards were then fabricated from the films.Generating a silkscreen layer was done, but it was time consuming.Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 04:01:33 pm
content: Quote from: Vgkid on March 02, 2014, 03:24:03 amVgkid,Here are a few pictures from the4275A, the 10 kHz to 10 MHz model.Front PanelHere is a picture of the 4275a measuring the capacitance and ESR of a small electrolytic capacitor:The 4275A agrees with the Jay_Diddy_B ESR meter adapterSo the 4275A must be goodOverviewThis shows a similar construction to the 4274A. This unit has option 001, 0-35V dc bias source:A1 Reference resistor assemblyWith the shields in place:Without the shields:This is a close-up of the reference resistors. The resistors are similar to the resistors in the 4274A. plastic tubing has been used space the resistors of the ground plane. There is also a more complex circuit for ac trims:Jay_Diddy_B

author: Vgkid
author_rank: Super Contributor
timestamp: March 02, 2014, 04:11:33 pm
content: Thanks for the added pics.

author: dc101
author_rank: Regular Contributor
timestamp: March 02, 2014, 06:33:48 pm
content: Quote from: Vgkid on March 02, 2014, 05:23:07 amSorry, I should have been more clear. I was curious what the potting was for on the transformers? Vibration? Heat? They look pretty cool, I thought they were massive caps at first.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 02, 2014, 08:09:48 pm
content: Quote from: dc101 on March 02, 2014, 06:33:48 pmI don't much about the inside of the transformer.It would make sense if they were toroidial cores. If they are toriodial transformers the plastic cup can be used to keep all the leads aligned.The potting compound would seal the transformer from moisture.It would prevent the transformers from being microphonic. This would prevent vibrations, especially from the fan, interfering with the measurements.I am sure it is not for power dissipation, these are low power signal transformers.Jay_Diddy_B

author: BravoV
author_rank: Super Contributor
timestamp: March 03, 2014, 02:41:46 am
content: Quote from: Jay_Diddy_B on March 02, 2014, 12:43:26 amFew years ago I was offered this exact fixture for about $150 nib, but I was not interested since I thought I need to have the LCR meter 1st which is hard to get. I guess I could make few pennies by reselling it at fleebay if I bought it ?

author: dc101
author_rank: Regular Contributor
timestamp: March 03, 2014, 02:46:08 am
content: Quote from: BravoV on March 03, 2014, 02:41:46 amMaybe, $150 seems to be what they're selling for these days. There's a couple people offering a buy it now price for more than $300, so I suppose it depends on how long you can wait. Jay's is in really good shape so something it that condition might go for slightly more.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 05, 2014, 01:53:58 am
content: Quote from: Jay_Diddy_B on March 02, 2014, 12:43:26 amThis was an approximation. There are some fixtures on eBay for $150.00. These are only include one of the three sets of inserts. You have to be lucky or spend a lot of money to get one with all the inserts.The BNC connectors on the front of the HP LCR meters are spaced 22mm apart. This spacing has been adopted by other manufacturers. You can also by other test fixtures like this one for around $60.00.The point I was making, an LCR meter with the fixture is worth considerably more than an LCR meter without a fixture.You can find many examples of Kelvin leads like these on eBay:These have to be modified to work with the HP 4274A and HP 4275A. The shields have to be connected together at the clip end of the cable:Jay_Diddy_B

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: March 05, 2014, 07:24:10 am
content: Awesome teardown!I was under the impression that the HP meters used the "Four-terminal pair" (4tp) DUT configuration. Its similar to the shielded four-terminal method, and both leads will function when hooked up. The difference with the pair method is current is carried on the shields of the Hcur and Lcur terminals, while the Hpot and Lpot terminal shields are just that, shields.Check me on this though...

author: TinkerGDS
author_rank: Contributor
timestamp: January 01, 2017, 06:08:04 pm
content: I found this thread very interesting. I just picked up a 4275A in very clean condition. When I first turned it on I initially got the battery error. I suspect the A9 battery is dead. I want to replace it, but the service manual has no information on what type of battery this is. Also, the service manual schematic shows the battery as 2.8v, but the battery on the board is 3.9v. I see in your A9 board pic, your battery is also an ElectroChem. Is your batter also the BCX-72-AA (3B64)? I removed the battery and found out it is a Li-Ion battery. Has anyone replaced these with a compatible type?

author: MateKrisz
author_rank: Regular Contributor
timestamp: February 04, 2017, 09:30:07 am
content: Hi all,I bought a HP 4274A. It used by an University. The original option labels has been removed I think. How can I check, what options installed?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: February 04, 2017, 10:32:12 am
content: Hi,Here is a list of possible options:From the picture, you have:001 or 002 I can't tell from the picture, but you do have the connector to control the internal bias supply.003 It is hard to tell. It isn't an important option.004 you can tell if you power it up and step through the test frequencies.101 you have, because there is an HPIB connector.The other options are not important.The green box is a modification somebody has done. The labels may be under the box.Regards,Jay_Diddy_B

author: MateKrisz
author_rank: Regular Contributor
timestamp: February 08, 2017, 09:51:32 pm
content: Thank you!I know more when the LCR meter arrived. I give you the 100. thanks!I got a picture, looks like the meter working fine.

author: mightyohm
author_rank: Regular Contributor
timestamp: August 04, 2017, 11:12:00 pm
content: Can someone share photos of their modified Kelvin clips? I'm wondering how to do this gracefully since the two alligator clips now need to be tethered to each other.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: December 16, 2017, 02:01:02 am
content: I realize this thread is old but wanted to leave this here for anyone who is in the market or may have one of these as well. I am not trying to high-jack the thread and cannot say enough thanks to Jay-Diddy for his work here. I am currently reworking my cheap-o ebay Kelvin leads according to his diagram and that video will be up soon. If anyone has any pointers for me, please feel free to comment here or on the video. Many thanks.video:Update: I probed all the Unknown BNC connectors on the front panel and checked to see if they all bodies, not the center line, go to ground. The H CUR (4th from left) does not, the other the have continuity. The BNC ground for 'H CUR' goes to board 3 from the left. Its the one with orange tab, via the mini-BNC cable. Does anyone know if this is normal, or could that be the Error 4 fault?Update 2: I made my own BNC cables and followed the flow chart from the service manual, page 8-33, and checked the voltage on A6-TP1 and adjusted it up to 500mV. I am not certain that the adjustment fixed it Error 4, or if it was just the cheap-o leads, but the meter is working now and I am stoked. Many thank Mr. Diddy!

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: December 19, 2017, 07:30:40 pm
content: Hi,You will get error 4 if the shields on the cables are not connected together at the test end of the cable.There is a diagram in this message:https://www.eevblog.com/forum/testgear/hp-4274a-lcr-meter-mini-teardown/msg399732/#msg399732If you take a piece of wire and connect all four shields on the front panel BNC connectors together error 4 should disappear.Regards,Jay_Diddy_B

author: Inverted18650
author_rank: Frequent Contributor
timestamp: December 29, 2017, 03:19:25 am
content: This was exactly my issue and the meter is now working “a treat” as Dave would say. Thank you Sir for the reply and the project you posted.

author: cncjerry
author_rank: Unknown
timestamp: December 29, 2017, 08:30:24 pm
content: might as well kick this thread all the way open. I have the version with the comparator on it, the HP 4262A. Once you have the kelvin style leads setup the meter is very accurate. I had to replace the front panel banana jacks as mine were so corroded they wouldn't tighten down on the shorting bar causing the error previously mentioned. It took me a few hours to track it down as it looked like the shorting strap was on the jacks and they were tight. One of those dumb errors that takes forever to fix.I also have the Agilent handheld, U1733C I think, bought it here when they were on sale for a good price, and the handheld does a great job. I've been thinking of retiring the 4262A but I sort of like it for sorting caps. The comparator is really handy once you calculate the range you need.Overall, the biggest challenge other than the power supply caps is all the front panel connectors and cables, at least on the 4262a. My last bit of advice in this area is that the handhelds like the U1733C will usually be more convenient, just about as accurate as at least the 4262A, and have some of the more common frequencies needed for testing ESR.~Jerry

author: MateKrisz
author_rank: Regular Contributor
timestamp: May 26, 2018, 07:18:39 pm
content: Hi,I have a 4274A, I bought long time ago, but just now wake up the unit.I made a little video about what do when starting. First time ok, but under 0,6 osc level with x1 multiplier send the error4 messages.It is normal? Or not?video:https://youtu.be/WGCp2Cpvr74Second thing, that I compared the original wiring schematic with what I found in this topic. I made a picture when see the different things.My question that need the red pinned shorts?Thanks!Regards,Krisztian

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 29, 2018, 06:40:54 am
content: Quote from: MateKrisz on May 26, 2018, 07:18:39 pmYes, you need the connections marked with red dots. This means connecting all the shields together. When you connect the shields together it will remove error 4.Regards,Jay_Diddy_B

author: MateKrisz
author_rank: Regular Contributor
timestamp: May 30, 2018, 06:36:07 am
content: Hi,Thank you your answer! I try it.Thanks!Krisztian

author: 3g57
author_rank: Regular Contributor
timestamp: June 01, 2018, 05:50:44 pm
content: Hello members of the forum!I did prophylaxis to my HP4275A and decided to add photos for you.Later, when I'll make the following photos, I will definitely upload photos for you with six modules.The device has worked more than 25 years.There were no problems.Sincerely, 3G57.p.s. I made a replacement for the bios battery twice. Last time in 2013.When You doing selftest follow this (video hasn't this):TEST LEADSThe device is very sensitive to changes from the factory TEST FIXTURE.When making their cords, the parameters * L * * C * * R * of the factory ones must be taken into account.(Electrical capacitance of the device, cable inductance, resistance of conductors.)These three parameters are necessarily present in any installation.Otherwise, the input circuit of the device will be unbalanced and it will not be able to adjust the input circuit during calibration.The input is unbalanced.The test will not be passed. The measurements are distorted!!!! SELF-TEST only with TEST FIXTURE 16047A.on others the test will not be passed! There will be errors!OPEN TEST enabled mode * C * BIAS *0FF*SHORT TEST enabled mode * R * BIAS *0FF*WRONG. SHORT TEST when C mode is onthere are errors !!!! BIAS *0FF*A5 A-D CONVERTER 04275-66505A4 PROCESSOR AMPLIFER 04275-66543A3 POWER AMPLIFER 04275-66503A2 MODULATOR 04275-66502A1 RENGE RESISTOR & NULL DETECTOR 04275-6650116023B BIAS CONTROLLERBest regards, 3G57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 02, 2018, 12:26:37 am
content: Hi all,I made simple 4 wire for my meter. I followed the 4T configuration. It is ok? Picture attached.On the display always reading ERR 4 messages. I started check the voltage on the test points.Here is the results:8-16 page:Initial settings, (Freq- 1kHz, Multiplier X1 etc, Osc Level: full cw) adjusted.A6 TP-1 - Sin 500mVrms - OKnext step:A3 TP-3 - Sin 3,3 Vrms- Exactly not ok. I measured 1Veff and I can change this value with osc level and multiplier. Is misprint in the service manual?next step:Wavefrom at high terminal: it's oknextDoes OP-1 - YesnextIs A5 adjusted ? - I'm here now.What do you think about the handmade "fixture"? The wiring good?Regards,Krisztian

author: precaud
author_rank: Frequent Contributor
timestamp: June 02, 2018, 02:47:44 pm
content: Quote from: MateKrisz on June 02, 2018, 12:26:37 amI don't think it is the cause of your ERR 4 message, but you don't need to connect the BNC shields at both ends of the cables. They just need to be joined at the end near the clips. That moves the reference ground plane out near the connectors.Also, it would be easier to use if you only had one alligator clip on each side, and connect the inner conductors to one clip on each side. After doing Open/Short compensation, there will be no difference in accuracy, especially within the 100kHz frequency range of the 4274A...

author: bugi
author_rank: Regular Contributor
timestamp: June 02, 2018, 03:05:58 pm
content: Quote from: precaud on June 02, 2018, 02:47:44 pmThere has been pics in this thread both with and without shield connections at the device end. To me, it makes more sense to have them without (i.e. only the clip ends connected). (Like in thishttps://www.eevblog.com/forum/testgear/hp-4274a-lcr-meter-mini-teardown/msg399849/#msg399849)Also, the ground "reference" or "plane" should be out there either way, but according to one of the pics, the clip end connection allows balanced currents in the drive cables. That is, not just one current going through positive drive center cable and the same current returning in the negative drive center cable, but also opposite currents in the drive cable shields'. (Whatever benefit that might give...)

author: 3g57
author_rank: Regular Contributor
timestamp: June 02, 2018, 03:28:03 pm
content: I think I need to check here

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 02, 2018, 07:26:29 pm
content: Hi all,Thanks 3g57 the amazing photos! I ordered the B+K TL89F1 fixture, somewhere I saw that is working with this model.I have the 04274-66523 DC Bias +100V board. I quick checked at A23 TP1, and A11 5R and here is nothing. :/Krisz

author: BravoV
author_rank: Super Contributor
timestamp: June 02, 2018, 07:34:20 pm
content: Quote from: 3g57 on June 01, 2018, 05:50:44 pmThank you so much for the details & superb photos.Photos saved locally.

author: 3g57
author_rank: Regular Contributor
timestamp: June 02, 2018, 07:50:31 pm
content: OK!Later I will give the following.

author: precaud
author_rank: Frequent Contributor
timestamp: June 03, 2018, 01:43:29 am
content: Quote from: bugi on June 02, 2018, 03:05:58 pmYes, that diagram shows them connected at the "clips" end. That is also as it has been specified in the HP Impedance handbooks.

author: 3g57
author_rank: Regular Contributor
timestamp: June 03, 2018, 03:30:58 pm
content: Krisz look at two places. I have indicated to you.I had a distrust of mine and I corrected it.Take the lens!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 03, 2018, 06:40:21 pm
content: Quote from: 3g57 on June 03, 2018, 03:30:58 pmHi,Ok, I check it now. A check the voltages at the TP points too. Do you replaced the old electrolytic capacitors in yours?Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 03, 2018, 06:54:15 pm
content: No, I did not change the capacitors.I'm not ready for this yet.After the replacement it is necessary to do the calibration.Time is not enough.He's still in the norm.I will make a replacement.The connectors in my power supply unit were undermined.You should watch this!!I need to make a test card for TP control.p.s. Krisz! Take a photo of your module at 100v.Lay out on the page!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 03, 2018, 08:20:11 pm
content: Hi,I resoldered the all connection on power board and measured the voltages of TP points, picture attached.I have an extension for ext DC bias:Inside:100V DC BiasP.s. I thinking about the extension. Well I bought from US, and a University used before. The picture about the extension taken is US and you see that INT Bias ON. It is worked over there. In Hungary, I made the handmade "fixture" and first time worked for me, but several hours later starting the ERR4 messages. I think maybe sometimes work the INT Bias sometimes not, and they used over there external BIAS supply too. What do you think?

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:58:11 am
content: Hi! Krisz. This is your module.15 left contacts + 15 right contacts x2 side.I have 18 + 18.You need to measure the stresses where I showed below in the attachment.I think I was not mistaken.I did not look at 15 right-wingers. They are in your module 100v.Replace R3 with multi-turn.Set -5v STD.!!!!!!+ 12v and -12v should be with great accuracy.This is a bipolar supply of operational amplifiers.Otherwise, it will be difficult to do correction TP.-3G57p.s. My.To your question:Internal DC-BIAS 35v & 100v will only work whenconnected to external control (16047A TEST FIXTURE) !!!This is a kit.The indicator (LED) on the front panel will be on!In this case, you should not turn on the calibration mode !!!Calibrate the instrument. * OFF * S4 on the rear panel.For your 100v module (04274-66523), you needcorresponding TEST FIXTURE (not 35v)!!!To use an external 200v to power,too, a corresponding TEST FIXTURE (not 35v)!!!According to your picture. Perhaps they used externalinput 35v for leak testing electrolyticcapacitors But this is dangerous for the entrance of the device.When testing a capacitor of high capacity and voltagethere is a possibility of its discharge potential at the input terminals.Before testing, it is necessary to discharge the capacitors !!!Otherwise, the spark and the possibility of damage- 04274-66523 DC Bias + 100V boardused to test the capacitance of transitions in transistors.This is done on this device.(draw a circuit board that's in the box! Interesting!In the box must be installed required voltage and current limited to 100mA)Check the test signal level and frequency on thecontrol points of quartz resonators.Perhaps the frequency has gone.When you rotate the oscillator knob, the signal is captured

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 07:06:28 pm
content: Hi,Thank you the useful informations! I measured the power board output voltages, and I found some not normal voltage value. The left side is working good, but the +44, -44, -22 exactly not. I used the common GND point.I ordered a B+K TL89F1 fixture. (https://hu.mouser.com/ProductDetail/BK-Precision/TL89F1/?qs=CjgjetG5vV4ukiCCEHhtpw==)It can:Test fixture for convenient testing of axial and radial leaded type components.Frequency: DC to 10MHzDC Bias:+/- 40V peak max (AC+DC)Operating Temperature: 0 to 40 degrees CTerminal Connection: BNC to 4 terminal insertion slots (radial or axial)Well, yesterday I bought on the eBay a 16023B bias controller (https://www.ebay.com/itm/HP-Agilent-Keysight-16023B-bias-controller/273240404664)I think with bias controller, they can work together the 100V bias board and the 40V fixture.I measured the osc level and freq on the H cur BNC socket, and seems to be ok.I attached a catalog sheet from '79 catalog.

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 07:14:29 pm
content: Hi! do not rush into conclusions about the common wirefor -44 and +44. At them it another. Look at the diagram.You can measure the voltage across the capacitors С5,С6._____________question:Measured with load?Measure under load on capacitor contacts.I marked GND & W3 Pin 2,3Only measure with load All points !!!!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 07:44:30 pm
content: Hi,Yes, now I see the GND. I remeasured but nothing changed. :/Yes I measured with load, the fully unit is working.

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 07:50:25 pm
content: Slightly understated +12 and -12.Will pass through the tires and the board will be even smaller.Better in the power supply a little more but always symmetrically !!!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 07:56:12 pm
content: Yes, but I have the original R3 and I wanna replace to multi-turn.Do you have idea why bigger the +-44 and -22 voltages?Before CR-13, CR-14 I measured 49,2 AC Volts. How?

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:01:52 pm
content: Check the AC switch on the rear paneldevice power supply voltage? 220/240If you have 220AC, then you can safely puton 240VAC. Just do not make a mistake!Then measure.Take off R3.Measure the resistance !!!On the new install the same.Only then install it!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:12:35 pm
content: Yes of course, because when arrived from US the first thing was that I swicthed from 120 to 220V.I have transformator I can use it 120V too.

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:16:38 pm
content: A transformer is not needed.Switch to 240VAC and measure now the voltage points!___________________________

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:41:46 pm
content: I switched up to 240V the primer. OMG what a collection!!!Grats!Try it on 120V? Maybe....Well the results:

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:44:56 pm
content: Is the tension closer to the truth?Check the work for a mistake! Er4

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:47:59 pm
content: Yes, but +44 and other still high yet. Try on 120V?ERR 4 message still flashing yet.

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:52:47 pm
content: Do not need a transformer.This is already normal.Wait for the purchase!Then you will look.Your entrance is open.But still there is a problem!Show more download videos.At the same time, reduce the frequency to 10 kHz x1

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 08:54:42 pm
content: The +12V on +44 it is normal?

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 09:00:35 pm
content: Ok, I wait both item. I hope will arrive in this week.

author: 3g57
author_rank: Regular Contributor
timestamp: June 04, 2018, 09:22:59 pm
content: It's late. I'm going to sleep.Best regards!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 04, 2018, 09:30:17 pm
content: Ok, I still bundle the tools. Thanks your help! Good night!

author: 3g57
author_rank: Regular Contributor
timestamp: June 06, 2018, 10:24:13 am
content: I wrote that the HP4275A worked without problems. And here is the problem. Breached the resolution of switching voltage 16023B BIAS CONTROLLER. The fault wasOctal D Flip−Flop with Clear. After the replacement, the normal work resumed.3g57

author: 3g57
author_rank: Regular Contributor
timestamp: June 06, 2018, 06:54:15 pm
content: MateKrisz! Hi!Have you drawn a scheme of a secret casket?

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 06, 2018, 06:58:38 pm
content: Hi,I hope all well with your 4275A!My packages on the way, I waiting...What asking?

author: 3g57
author_rank: Regular Contributor
timestamp: June 06, 2018, 07:14:33 pm
content: Everything is normal! LS - the series is weak. Unreliable.ALS is much better.Therefore also has died.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 06, 2018, 07:21:49 pm
content: It is not sounds good, can I help you?

author: 3g57
author_rank: Regular Contributor
timestamp: June 06, 2018, 09:21:43 pm
content: MateKrisz! I will draw Extender boards.I think the HP4275A needs to be calibrated.3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 06, 2018, 09:37:28 pm
content: Hi,It is interest, never seen before. And what extend with this board?

author: 3g57
author_rank: Regular Contributor
timestamp: June 06, 2018, 09:46:07 pm
content: This was done for NIKON equipment.I will do this for the HP4275A.This one does not fit.3G57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 07, 2018, 09:43:14 am
content: Quote from: 3g57 on June 06, 2018, 06:54:15 pmYes, I will send you at tonight.Krisz

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 07, 2018, 07:34:30 pm
content: Hi,Here is the schematic of the little box. The bigger diode type is not clean for me. I hope it helps you:Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 07, 2018, 08:15:29 pm
content: 1.5SE36A (NTE4940 analog)Overvoltage Suppressor 36V .Protection against higher voltage.Suppressors are usually used in impulse power supplies.They protect against voltage surge.Installed on the primary winding of the transformer.As I wrote the box gives a certain voltageand limits its current to 100mA.3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 07, 2018, 08:23:25 pm
content: Ok, thanks!The fixture will arrive tomorrow!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 11:27:49 am
content: Hi,The fixture arrived, and I could not wait, I opened the box and installed the fixture. I followed the open and shorts test procedure, but not succeed. ERR 1 and then ERR 4 flashing :/Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 12:44:42 pm
content: Hi! Krisz!I did not know that you would buy the option 16023B BIAS CONTROLLER.You hurried. You should have bought PM2811 for this price.You would have got one more device and it was run by DS BIAS!I work this way.How to calibrate PM2811/PM2813 it I described here!https://www.eevblog.com/forum/reviews/phillipsfluke-pm2811-power-source/msg1322150/#msg1322150He has a discreteness of 1mV. Learn.It allows you to limit the current.3g57p.s. I uploaded your HP4274A circuit yesterday.Has studied. You have a problem in A3.I will write later. You need to do measurements on A3.

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 01:36:40 pm
content: Quote from: MateKrisz on June 08, 2018, 11:27:49 amIt is necessary to make measurements.I think you have a problem with the signal level on A3.You need to check:1. Input BNC connectors. Cable from them to leak2. R28 - loss of contact or poor contact.3. Voltage to CR1, CR184. In А3 - ТР2, ТР3,5. key Q2,3,46. the key Q10,11,12,13,147. carefully U5. Comporator LM339P she manages the keys.you need to get passport modes on T3 and T6.Remember that the common points are different!I hope that the power supply voltage of the module is normal.The following models did not use an operational amplifier. The discrete elements were installed.Perhaps this is more reliable.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 05:45:38 pm
content: Hi,Thank you! I now measure the suggested areas.I come back later with values.Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 05:50:28 pm
content: Quote from: MateKrisz on June 08, 2018, 05:45:38 pmYour x10 AMP is not working well.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 06:03:23 pm
content: On A3 board?

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 06:05:23 pm
content: Quote from: MateKrisz on June 08, 2018, 06:03:23 pmYes! VERNER AMP.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 06:51:28 pm
content: Well, I check the list, here are the results:R28 10 ohm - OKA3 TP2 34mvA3 TP3 -7mVIt is interesting, I just checked.A6 TP1 -10mVA6 TP2 -2mVA6 TP3 +2,5VA5 TP1 +5,97VA5 TP2 -5,97V

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 07:03:12 pm
content: You wrote to me that with the oscillator is normal!Now go from the oscillator!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 07:04:53 pm
content: Yes, it was normal and worked fine, but now I just checked and you see that what measured. :/

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 07:07:04 pm
content: Quote from: MateKrisz on June 08, 2018, 07:04:53 pmDo not understand.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 07:15:08 pm
content: I checked the test signal on H Cur with the scope. Pic attached. Here is the test signal nice sin wave and the levels is ok.

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 07:26:15 pm
content: Open the manual and see FIGURE 8-31.Follow the path.DSA2 is a TRD DECODERBottom left.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 07:36:28 pm
content: OK

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 08:22:10 pm
content: Sorry, first time I made a bad measurement :/Well, the correct is:R28 - 10 ohm - OKA3 TP2 3V rms - 1 kHzA3 TP3 1V rmsA3 TP1 500mV rms (it should be here 7Vpp), replace T3 T1? ->http://hu.farnell.com/murata-power-solutions/76602-1c/transformer-pulse-1-1-1/dp/1087810A6 TP1 500mV rmsA6 TP2 600 mV rmsI hope it helps.Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 08:51:42 pm
content: TP1, TP4?Are the transformers identical?swap places. look!A6 TP2 = 1.5VP-P is the norm.see above FIGURE 8-40.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 09:02:18 pm
content: at A3 TP4 should be 3Vpp but there is nothing.I think need replace the A3 T2 too. This is the correct replacement:http://hu.farnell.com/murata-power-solutions/76602-1c/transformer-pulse-1-1-1/dp/1087810

author: 3g57
author_rank: Regular Contributor
timestamp: June 08, 2018, 09:20:17 pm
content: Try it!check again the sigils A6.output A2You have a problem in a weak signal.You rotate the handle of the oscillator to the left and from the middle you clean it completely.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 08, 2018, 09:27:10 pm
content: Ok, I check with the Figure 8-40.

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 12:06:51 pm
content: Krisz! Hi! Make yourself on the HP4274A.I do not have a good file for this. I made an example for the HP4275A.You will be more clear.Do not confuse RMS and P-P with measurements. You're close with the problem.Do not rush.Observe such conditions with respect to HP4274A.They are different from you.3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 02:43:28 pm
content: Hi,Yesterday I had a small problem with my scope. I fixed it first.Today I rechecked the following test points, I followed the charts.Figure 8-16A6 TP1 500 mVrms - OKA3 TP3 3,3 Vrms - I measured 1 VrmsGo to A3 troubleshooting Figure 8-31A3 TP2 8,4Vpp - OKControlled by vernier? - yesA3 TP3 All amplitudes (0.01 , 0.1 , 1 , 5 Vrms) - All OKA3 TP4 3 Vpp - I measured 1.6 VppCheck A3T2 transformerI checked to the A3 TP1 7Vpp - I measured here 1.6 VppCheck A3T1 transformerIt is possible that both transformers have been broken?TDK 113G1 used and this is compatible with this?http://uk.farnell.com/murata-power-solutions/76602-1c/transformer-pulse-1-1-1/dp/1087810Thanks!Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 04:08:15 pm
content: T2 may have broken down.T1 - I do not think it burned outCheck the keys and the comporator!T2 is installed at the output. K through it could discharge the capacitor.Check Q4.!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 06:03:49 pm
content: Ok, I solder out.1040 hFE with a multimeter. I think it is ok.

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 07:29:04 pm
content: You can check the transformer in any circuit or generatorif there is a low output impedance.U5-?If the transformers are identical, change between them.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 07:44:49 pm
content: CheckingI ordered U5 to U10 new ICs. I don't have the place to check the U5 when the card is inserted.

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 09:46:35 pm
content: Quote from: MateKrisz on June 09, 2018, 07:44:49 pmU5 replacement with a new one. So faster.Just install it on the panel.The transformer must be removed and connected to the generator.Emulate the signal is real!The secondary winding of the load and see the amplitude level and waveform.If it's bad you'll notice.I installed the Sockets!Here is a weak spot. Therefore it can happen again.3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 10:32:05 pm
content: Hi,Quick I soldered out the A3T1.Source: 1Vrms 1kHz sin waveHere are the results:N2N3It looks good?

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 10:40:31 pm
content: not happy.what signal at the transformer input?Try the second one. for comparison.Do not confuse the transformers.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 10:45:05 pm
content: Source: 1Vrms 1kHz sin waveI try the second now.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 11:09:52 pm
content: Here is the A3 T2.Source same: 1Vrms 1 kHz sin waveN2N3Both transformers output similar. Both good or both bad?

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 11:10:55 pm
content: You can assume that he is normal.Two could not burn.In this way, check the output transformers. Only necessaryload them.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 11:14:30 pm
content: Good news that they are good. Do you think as output transformer A3 T3, T4, T5?

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 11:18:58 pm
content: Quote from: MateKrisz on June 09, 2018, 11:14:30 pmIt is necessary to check at least this way.With a good generator and Extender boards, everything was much easier. Disconnect the input. At the input of the cascades, give the necessary signal and follow the path of the oscillograph with the oscillograph. Watch where he is lost.p.s. Krisz! soon morning. I'm going to go to bed.Send me screenshots!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 11:27:50 pm
content: Now I know what the extender board is good for.I have a Philips signal, it can everything.Disconnect the signal, do you mean A3 J1?

author: 3g57
author_rank: Regular Contributor
timestamp: June 09, 2018, 11:31:48 pm
content: Quote from: MateKrisz on June 09, 2018, 11:27:50 pmTransformer input T1.Do not rush. Till tomorrow!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 09, 2018, 11:43:24 pm
content: Ok, tomorrow continue. Good night! :-)

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 10, 2018, 06:10:54 pm
content: Hi,I checked the BNC sockets, on the front side.It is missed from your the checklist what you wrote. All wires tested for shorts to chassis. No shorts between the pairs too.Lc - Blue wire - OKLp - Red wire - OKHc - Yellow - OKHp - White - OKKrisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 11, 2018, 10:17:50 am
content: Krisz! Hi!You have another option.Take out the module and on the table give him the necessary + 12V / -12V.On T1, give the necessary signal. Next, with an oscillograph, look at it.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 11, 2018, 06:56:48 pm
content: Hi,I found an interesting article about, how to test the pulse transformers.https://scienceprog.com/testing-pulse-transformer-with-an-oscilloscope/I checked both transformers secondary n2, n3 and all right. You see in the scope pic.The Bias Controller arrived.I bought U5 - U 10 ICs. I replace them, it is maybe slowly because I hate desoldering ICs from PCB.

author: 3g57
author_rank: Regular Contributor
timestamp: June 11, 2018, 08:59:20 pm
content: Signal levels are performed by U5.This is the table.Gives commands from the DSA- TRD DECODER.You have a weak signal level.Here's your task.When you set the potentiometer signal to the maximum you do not have an error. Do I understand correctly?It was on the video.If you have cascaded amplifiers in good order, then you need to search for the reason with the teams!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 11, 2018, 09:29:31 pm
content: Hi,Today I bought U5 IC it is called LM339N and sockets. It is a good replacement? I replace first time the U5 now. I don't have any space for the measure when the card is insertedMay I solder on the pins of the IC little wires, but it is very homemade version... what do you think?I tested the Bias controller, looks like it is working!

author: 3g57
author_rank: Regular Contributor
timestamp: June 11, 2018, 09:42:02 pm
content: Quote from: MateKrisz on June 11, 2018, 09:29:31 pmI did not understand the question.What to solder?

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 11, 2018, 09:46:25 pm
content: If I insert the card, I don't have any space for measuring. But if I solder short wires on the U5 339IC pins, I can measure the correct DC levels? I know it is very amateur, but I don't have extension cards yet.The LM339N good for U5?

author: 3g57
author_rank: Regular Contributor
timestamp: June 11, 2018, 09:51:19 pm
content: You first plug in and turn it on. Will there be an error?To solder to it is not a good option!If you are sure that there are no problems with amplifiers and after the replacement of U5there is an error then there is no command on U5.The signal with U5 can be checked in the key bases Q ...... QThey are installed at the top and they can be reached.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 11, 2018, 11:04:40 pm
content: I am replaced the U5 but nothing changed. ERR 4 still flashing. Do you think Q2 to Q5?Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 11, 2018, 11:11:05 pm
content: Maybe. It is necessary to change.It is desirable to measure the levels c U5.U5 adjusts the signal level at the output U2.R14 at the output U1.How do I remember the output of U1 was close to normal?

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 11, 2018, 11:17:21 pm
content: Ok, I try to measure the transistors.What level need there?I not measured yet the U1 output voltages.

author: 3g57
author_rank: Regular Contributor
timestamp: June 11, 2018, 11:24:01 pm
content: Quote from: MateKrisz on June 11, 2018, 11:17:21 pmYou have a table.In bases Q ..... Q on the command table with logical levels.

author: 3g57
author_rank: Regular Contributor
timestamp: June 11, 2018, 11:29:13 pm
content: Quote from: MateKrisz on June 11, 2018, 11:17:21 pmYou wrote me * A3 TP2 8,4Vpp - OK *I rely on it!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 12, 2018, 03:29:36 pm
content: Yes, it is. I confirmedSorry I just mixed up.I measuring the Q2-3-4. In progress.

author: 3g57
author_rank: Regular Contributor
timestamp: June 12, 2018, 06:09:27 pm
content: Quote from: MateKrisz on June 12, 2018, 03:29:36 pmHi!You need to go through the check oncascades and set the required signal levels.This is just the top of the A3.Similarly, it is necessary to pass the bottom of A3.Because they work synchronously.I'm showing you on the screen.Unfortunately I do not have a good file.This is not all legible.3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 13, 2018, 08:07:50 pm
content: Hi,I measured the Q2, Q3, Q4Values:Multix0,01x0,1x1x5Q2 out after R24-10,98-10,98-10,98+6,4Q3 out after R25+6,4-10,98-10,98-10,98Q4 out after R26-10,98+6,4-10,98-10,98I measured the DC voltage on A3 L2 and there is +11,2VI measured on U5 14 pin the DClevel (for more pin need a little more space for checking, but I don't have)x0,01 - -10,98x01 - -10,98x1 - -10,98x5 - -10,98In x1 position need + voltage or not?Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:17:50 am
content: Hi! Krisz.I watched.This module has two common buses.1- digital2- analogWhen you take measurements take it into account !!!You should first of all make measurements of the signal levels at the input U7 / U6 / U5.This way you can check the low and high levels of signals and compare with the table.U7 / U6 / U5 create a signal level for the analog partand send it to the keys Q2 / Q3 / Q4, Q10 / Q11 / Q12 / Q13 / Q14.A high and a low level is better measured by an oscillograph. In DC open mode.!!!Make a table for yourself.!On your question:Extender boards buy for yourself convenient.If you want, you can wait for me next week, I can sendyou need a file to make it.This mine, but it is not high. There will be another, adapted for HP4275ACheck D-GND! So on the board?________________________________3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 05:00:28 pm
content: Hi,Just a quick question. For the sake of clarity I ask it:A-GND - A11 11-13LD-GND - A11 7RWhat are on A11 4R? (Bias Monitor RTN) It is same as A-GND?I just checked the A11 board again and A-GND and D-GND and 4R are on common potential and connected to chassis. (All boards inserted)Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 06:07:59 pm
content: 1- The analog common bus typically suppliesoperational amplifiers, etc.2- The digital common bus usually supplies logic elements, CPU, etc.They can communicate under certain conditions. As a rule, this is donethrough the denouement.At this device I watched 4 tires !!!!You can find the answer to the second question in this diagram.I painted her color.Here the screening braid has its meaning.It additionally performs an active role with a certainconnection. Learn. It is important.Pay attention!!!! On the numbers in the triangle!This is an example with the HP4275A

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 07:20:31 pm
content: Hi,Here are the quick results:Multi x0,01 x0,1 x1 x5U5-4 L H H H (U5 replaced)U6-4 H H H HU7-4 H H H HHigh is +4V DCGND A11-7RIt is good?More results in progress.I don't have numbers in the triangles on the schematic.D-GND between A11-R7 and U8-10, U9-10, U10-10 are OK.Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 07:57:03 pm
content: Quote from: MateKrisz on June 14, 2018, 07:20:31 pmKrisz.What is U5-4, U6-4, U7-4?

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 08:10:43 pm
content: You need a level only U5 !!!So far only at her entrance.See the table.Signal to U5 inputTLHT - pin10TLS#1 - pin8TLM - pin6TLL - pin4Make a table for yourself when multiplexer is running.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 08:32:34 pm
content: Here is the table:Multi x0,01 x0,1 x1 x5U5-4 L H H HU5-6 L L L LU5-8 H H H HU5-10 H H H HU5-10 is U5-pin10

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 08:50:28 pm
content: Check. I'm not wrong.This is the table.Check now the levels at the output of U5, only relative to the analog common bus of 12L.Make a table.!p.s. I rely on your measurements.If they are right, then you have a problem up to U5!ATT does not work correctly. Therefore, further error.It should also be taken into account that U5 controls the lower part of the circuit A3.This will also be a mistake!3G57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 09:23:37 pm
content: Hi,I measured again with same as your table.Multi pin10 pin8 pin6 pin4x5 L H H Hx1 H H H Hx0,1 H H L Hx0,01 H H H LBut it is normal that the Hcur signal on the Bias monitor socket?Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 09:29:30 pm
content: Quote from: MateKrisz on June 14, 2018, 09:23:37 pmThis does not correspond to the norm in the table!So it does not work properly!

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 09:32:41 pm
content: Quote from: MateKrisz on June 14, 2018, 09:23:37 pmUnderstand the scheme!I did not penetrate.________________Yes. Through the resistor R43

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 09:43:08 pm
content: Check the levels on U5 pin1, pin2, pin13,14?I just asked the signal level at Bias monitor, never check this before.But don't understand how not work properly the U5 when on Hcur socket the signal levels are correct.

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 09:48:24 pm
content: Quote from: MateKrisz on June 14, 2018, 09:43:08 pmCompare the table and your measurements.You have a problem up to U5 !!At the output of U5, you have not measured.p.s. Yet. Read in the manual. Measurements must be made with the connectedTEST FIX. 16047 or without it ?? It is important!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 10:30:26 pm
content: Hi,I check the U8-9 levels?I attached the fixture.

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 10:36:41 pm
content: Quote from: MateKrisz on June 14, 2018, 10:30:26 pmOnce again, check the U5 levels after installing the TEST FIX. 16047Make a table.!With U8 / U9 later.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 10:39:10 pm
content: Ok, just a moment.But the fixture, not original 16047, it is B+K Model TL89F1.

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 10:40:29 pm
content: Let it be for now.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:08:28 pm
content: I repeated the U5 measure, and nothing changed.The B+K fixture working with 4274A. Here is the article:http://k6jca.blogspot.com/2017/11/replace-hp-16047a-test-fixture-with-bk.html

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:16:39 pm
content: Krisz!Hence it is necessary to replace U8, U9, U10.Install the sockets for them. It will be faster than checking !!!You can not do this.p.s. You can try, maybe they are good?Perhaps the problem is up to them.3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:27:35 pm
content: I hope! Tomorrow the first thing will be that I replaced them! :-) Thanks your help!KriszHow test these ICs?

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:31:57 pm
content: Quote from: MateKrisz on June 14, 2018, 11:27:35 pmReplace! They are not expensive.Install it in the sockets.Replacement only for the same.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:34:39 pm
content: ok, I bought sockets and ICs some days ago. I can replace them quickly.

author: 3g57
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:38:24 pm
content: Krisz! I did not study the manual on the HP4274A.With HP4275A they have a difference!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 14, 2018, 11:55:54 pm
content: I waiting the morning! :-) If I replaced and the open and short calibration succes we are ok :-)

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 15, 2018, 07:12:26 pm
content: Hi,I replaced the U8-9-10 IC-s but, ERR4 still flashing.Please check the service manual 5.19 section. Maybe it is important.Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 15, 2018, 07:43:09 pm
content: Hi. measure logical levels now.Until you restore them, the car will not go.The analog part here does not take part.Your signal levels do not correspond to passport standards. The multiplexer controls these signals. It is necessary to bring this back to normal.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 15, 2018, 10:04:34 pm
content: How can I restore when I measured the logical levels?For this measure on A7 need the extension, because of the ICs at the bottom side of A7 board.

author: 3g57
author_rank: Regular Contributor
timestamp: June 15, 2018, 11:03:52 pm
content: A7 do not touch yet.You need to measure the levels again at the input of U5.Make again the table and compare it with the previous one.Further in the chain on A3, you did not check the last node.This is LATCH! It can inhibit the passage of the signal to U8 / U9 / U10.To do this, it was installed. With him you need to understand.3g57

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: June 16, 2018, 01:57:21 am
content: Hi,I have been following this thread. Are you sure that your HP4274A is broken?Let me show you what happens with a perfectly healthy 4274A.If I press the ZERO open button with no fixture connected to the HP4274A Err 1 is displayed:If I connect an HP16047A fixture to the HP4274A and press ZERO open, the HP4274A displays CAL until the ZERO open is complete:If I connect all the shield of the BNC connectors together and connect Lcur to Lpot and Hcur to Hpot and I press the ZERO cal the test is performed the same way as with the 16047A fixture:Here is a close up of the wires:The BK Precision Test fixture may not be wired the same way as the HP fixture. I would check it.Regards,Jay_Diddy_B

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 16, 2018, 08:30:15 am
content: Hi,I tested the zero calibration with simple wires, but first time CAL, ERR1, and ERR4 flashing.In zero offset adjustment need to set the multiplier in x5 position? the user manual says yes.I found an article that BK fixture working with 4274A.http://k6jca.blogspot.com/2017/11/replace-hp-16047a-test-fixture-with-bk.htmlI think need to work the fixture with 4274A.A little history: When arrived the 4274A first time worked, but I don't had a fixture. I made a handmade fixture using alligator clips, and it is worked. I could measure R C L parts. Then I left from my workshop, but the 4274A stayed power on. 2 hours later I came back, and ERR4 flashing on display. I don't know what happened, nobody touched the 4274A.Can you send me a similar photo from 4274A? Need compare with yours. You see this if Push the SELF Test and D button.Thanks!Regards,Krisz

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: June 16, 2018, 10:23:28 am
content: Krisz and the group,Here is the self test section from the manual.This is a summary:Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: June 16, 2018, 10:26:27 am
content: Hi,Here are the results from my 4274A with the 16047A installed:Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: June 16, 2018, 10:28:13 am
content: Hi,The rest of the self-test results:Regards,Jay_Diddy_B

author: 3g57
author_rank: Regular Contributor
timestamp: June 16, 2018, 11:06:33 am
content: Hi! Krisz.The only digital bus that goeson A3 this is STROBE CLOK DECODER.She manages DSA-2. Even when checking (see FIGURE 8-31), I send the instruction to the address U216 (MC U20 74LS74N).Here, a signal is generated for the digital part A3.This creates the necessary signals for U8, U9, U10. LATCH.A task:It is necessary to achieve the normal operation of these microcircuits(MULTIPLEXER).3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 16, 2018, 04:58:11 pm
content: Hi all,Quick I made a video about the self-test:At A3 TP3 I found 1Vrms. But this value depends on FREQ and Multiplier settings.Flowchart wants there 3,3Vrms. How could be 3,3 Vrms if depend on multiplier?Multiplier x1, FREQ 1 kHz:I checked the A7 board test points:A7TP10 - Hi-Lo switchingA7TP11 - Hi (+4V)A7TP12 - Hi-Lo switchingA7TP13 - HiA7TP7 - Hi (+5V)A7TP18 - HiA7TP5 - LoKriszPS.: May I replace the A7 U20?Thanks!Krisz

author: 3g57
author_rank: Regular Contributor
timestamp: June 18, 2018, 09:03:43 am
content: Krisz! Hi.You can replace U20. Install it on the socket.Look at the situation.You make measurements and do not specify under what regime it was done! It is very important. You give the results of measurements. How can I guess? The digital part does not work correctly.Look at your last measurements! Tp11-A7. pin # 34 * RESET *.You have a high level on it. It is activated.The * ENABLE * Tp10-A7 pin # 25 is followed by continuousswitching (A7TP10 - Hi-Lo switching).Why is this happening and under what conditions?It is necessary to measure the reference frequencies of quartzresonators. Pretty sure. The instruction writes about an error up to 20ppm.There are three quartz resonators.* RESET * can occur due to the breakdown of the reference (inaccuracy) frequency.p.s. I asked the mail about the battery. There was no answer.You can not do without an expansion board.3g57

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 18, 2018, 08:18:24 pm
content: Hi,Sorry, I just now see your messages. I did not get an e-mail about the new post and the PM message. I ordered the U20 IC, it is will arrive circa Friday.I always made the measurements with the default settings, except if flowchart or you don't want other settings.On my 4274A not installed the memory backup option. If exist other battery where can I find it?I think I order 2 extension card from the original manufacturer:http://www.douglas.com/index.php/6-de-6.htmlwith sockets. I ask them, what is the real shipping cost because the calculator said 100-200 USD. It is too expensive for these little cards.Krisz

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 19, 2018, 04:58:10 pm
content: Hi,It is my A9 board w/o battery. I measure again on the A7 board?Krisz

author: precaud
author_rank: Frequent Contributor
timestamp: June 20, 2018, 03:40:02 am
content: As I discovered when repairing my 4275A, you are better off leaving the battery out while troubleshooting. Also remove the GPIB board (and DC bias bpard if it has one) until you find your problem(s).

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 20, 2018, 09:22:06 am
content: Good idea! Thanks!

author: precaud
author_rank: Frequent Contributor
timestamp: June 20, 2018, 12:36:02 pm
content: Also remove the socketed EPROM labeled "19", that is for the GPIB board.

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 20, 2018, 07:43:56 pm
content: OK!

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 20, 2018, 07:57:53 pm
content: Hi 3g57,The U20 IC has arrived. I replace them. Maybe it was broken.Update: Replaced but nothing changed. Still ERR4 flashingKrisz

author: MateKrisz
author_rank: Regular Contributor
timestamp: June 25, 2018, 06:50:23 pm
content: Hi,The brand new original Sony C1636 transistors have arrived. I tested them, and replace on A3 board.Krisz

author: MateKrisz
author_rank: Regular Contributor
timestamp: January 07, 2019, 07:40:15 pm
content: Hi all,Looks like my HP 4274A working fine finally. Thanks for the useful informations and tips for all. It was a long adventure, and I learned a lot of things about the world of the TTL. Little later i make a post and I will write the repair process, I have tons of pictures and some useful info, maybe helps for somebody. And well now I will open a bottle of beer.

author: velik_kazakov
author_rank: Regular Contributor
timestamp: January 08, 2019, 07:05:13 am
content: Santa Claus come to me toowith working 4274A in good working condition.My A9 board is different compared to the pictures I find in the net. Want to ask if someone have backup of the eproms for this board (part numbers 04274-85041.... 04274-85046). If not I think to try to read it w/o desoldering from the board. Think to solder a dip in the empty place and to desolder only the ROM selector. After to try to select every eeprom and to read it. What you guys think about this or need to desolder every eeprom and to read it.

author: MateKrisz
author_rank: Regular Contributor
timestamp: January 08, 2019, 08:19:13 pm
content: Hi,Yours very nice too! I think only way if you desoldering the ROMs. After you can solder the correct sockets and push the original ROMs. My different, little earlier than yours. Just a question. Your equipped with 001 or 002 option? Mine is equipped with 002 option, 100V BIAS card, and if I set the second position (<2F 35/100V) on the rear panel I can't measure over 200nF. I really don't know it is normal or not.

author: velik_kazakov
author_rank: Regular Contributor
timestamp: January 09, 2019, 06:23:41 am
content: Hi,my options - GPIB, 35Vdc bias, Battery. Will try this night about this measuring and will let you know. Get a box with fixtures too with my unit.Some are from other HP equipment but can be used with small mods.BTW on the first picture is connected 1000uF electrolytic cap with dc bias 28.5 v. All looks correct.

author: MateKrisz
author_rank: Regular Contributor
timestamp: January 09, 2019, 09:02:17 pm
content: Hi,Thanks for your answer! Today I read in the user manual the following: "Note: Option 002 internal dc bias should be used for capacitance measurements below 0,1uF." I think because the 35Vdc bias card voltage accuracy is 0,5% and the 100Vdc bias option has 2%.So I need to change the bias card to 35Vdc version or I need a 16047B fixture and I can use the 200V Bias option if I would like to measure higher capacity than 0,1uF with Bias.I saw your plus fixtures. Looks good!Do you have an unused fixture for sale?Here are 2 picture of my measuring. You can compare with yours. The HP 3456A show the current bias voltage.Krisz

author: velik_kazakov
author_rank: Regular Contributor
timestamp: January 10, 2019, 07:36:16 am
content: Hi,I have no time yesterday to test the measuring of big caps with dc bias , but will do this today.I have some 16048 fixtures, but all are with broken clips. Maybe will use one of them to do a fixture like 16047. I have no 16047 in the set. Something else - I have one good probe from HP 4328A (like on this pictures -https://www.woutersenwouters.be/sold-products/101/hewlett-packard-4328a-milliohmmeter-with-hp16005a-clip-type-probes). They use this socket RM12BRD-5S-71 HRS Hirose (https://www.ebay.co.uk/itm/Connettore-circolare-5-poli-femmina-RM12BRD-5S-71-HRS-Hirose/223317913580). It is very strong clips and one that I have are in very good condition + extra 3 spare clips. I think to order one socket and to install it on a 16048 to be used with this probe. It looks good for in circuit measuring. The clips are very fine on the ends. BTW I have one test fixture 16096A tha I can't use. I think to try to sell it and when sell it to buy one original 16047 A or B for my 4274A. If I find some time in the future will use one 16048 to do it for SMD elements.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: January 11, 2019, 02:09:14 am
content: NICE SCORE. The adapters are a small fortune too.

author: velik_kazakov
author_rank: Regular Contributor
timestamp: January 11, 2019, 07:21:12 am
content: I do some tests with DC bias and 3300uF cap. No problem to measuring this cap. Just the setting time for the bias is longer. Here have some pics with 0v, 10v and 20v bias.BTW, find a cracked Rifa cap inside the item, exchange it with new one. If it blow they generate lots of smell for some days in the room. I still remember this smell from last one that blow in my hands. This Rifa element is hidden under the AC traf and need to remove the traf to reach and exchange this cap.

author: MateKrisz
author_rank: Regular Contributor
timestamp: January 11, 2019, 12:38:14 pm
content: Hi,Thank you for the pictures of your measurement. I really don't know what happen at me, because when I try to measure a 47uF capacitor with 5V Bias, I see how charging very slowly and just Err4 flashing. I will try to order a 001 option +35Vdc card. If you sell I wanna to buy a 16048 with broken clips.With the 4274A working well the BK Precision TL89F1 fixture too. It is much cheaper than original HP/Agilent 16047A. See my attached picture.https://www.mouser.bg/ProductDetail/BK-Precision/TL89F1?qs=%2fha2pyFaduhLmatVqNnrkFl7T9kQbnjqWyUnSv4N2%2fx4a2gZHtHWyA%3d%3dorhttps://www.globaltestsupply.com/product/bk-precision-tl89f1

author: velik_kazakov
author_rank: Regular Contributor
timestamp: January 14, 2019, 12:05:20 pm
content: Quote from: MateKrisz on January 11, 2019, 12:38:14 pmHi,maybe will order one TL89F1 in the future. For now will use 16048 - it work perfect. If you want I can to make some pictures in the weekend of the test fixtures and if you have an interest of it to comment with me. Maybe will use one of them to use it and to make it for SMD. Have a friends that will do all parts that need to do all, but have no time now for this. Most impotent for me is to find a time to back up the eproms.

author: MateKrisz
author_rank: Regular Contributor
timestamp: January 16, 2019, 10:51:24 pm
content: Hi,Yes it is good idea! The BK has Smd fixture too, really not expensive. I asked my friend about ROM backup. He can save it and write another epproms, but need remove the eproms from the PCB. My CPU board is different, and I my rom images not compatible with yours unfortunetly.

author: precaud
author_rank: Frequent Contributor
timestamp: January 17, 2019, 04:28:47 am
content: 4274A and 4275A use same ROM images. See:https://www.eevblog.com/forum/repair/the-repair-from-he!!-hp-4275a-lcr-meter/msg1490586/#msg1490586

author: velik_kazakov
author_rank: Regular Contributor
timestamp: September 19, 2020, 06:48:01 am
content: Want to post something for my 4274A. It die before a week and yesterday night I find a time to repair it. Before to start I read some topics here and order some 74ls chips and some ram chips to have on hends when strat to do it. I check the PS and all looks good, no ripples and all are in specs. Start to check the microprocesor board and find clock , reset and PS are OK. Based on the precaud experience with 4275A I check RAM chips first. I find and order 3pcs here in local market CM8114 (Bulgarian analog of 2114). All NOS and 2 of them are gold plated ceramic chips. Testing all on wellon programer just one in plastic pack are good. I remove the RAM chips from the board and install ic sockets. Test both RAM chips from the board and get both are not good on the programmer. When I replace first chip with new one the instrument power up w/o any errors. It was alive agin. After that I try to replace both chips with RAm in ceramic body and all power up. Maybe there have some bad sells in the RAM chps, but the instrument don't use it and work well. Now my HP 4274A is "uprgaded" with Bulgarian made NOS RAM CM8114 and work well. Thanks to all that discuss that problem.Cheers!

author: w3jn
author_rank: Newbie
timestamp: August 14, 2025, 05:20:48 pm
content: I'd rather not start a new thread on the 4274A since this thread seems to be the gathering point for info on this meter, but I did want to share my repair experience.Bought on eBay, decent condition and advertised as not-working. Power up successful, measured OK but measured values would change when adjusting the test level on the 1V and 5V ranges. Doing a self test netted OP3,4,5,10,11,12 and probably more I forgot about. Trying the specific self-tests 3,4,5 and 6 netted "OF" in the left display. The voltage at the output seemed OK as measured with a scope, as did the internal Vtest display.Trouble pointed to the A4 board. Indeed, looking with a scope at the test points the waveform was clipping although the input was fine. The amplification/attenuation factor of the op amps on this board are selected by biasing a FET to switch in and out various resistors. These in turn are driven by LM339 comparators, who are in turn driven by 74LS273 latches on the A5 board. Keeping in mind a 4275A I repaired some years ago had a half dozen bad LM339s, I immediately suspected them.There is also a "A/D converter" on the last stage which again consists of a LM339 quad comparator, and each section switches in/out resistor combinations. The LM339 is fed by the front panel Vtest pot thru a op amp buffer. The inputs of the LM339 were fine, but the outputs didn't shift at all. Replaced the LM339 and that part of the circuit worked fine but I still had all the OP test errors.Looking at the stage where the clipping was happening, it was apparent that a couple of the gain resistors were'nt being switched. And that led back to a bad 74LS273 on the A5 board. Replaced the 74LS273 and now had good signals at the inputs of the LM339 but nothing was happening on the outputs. Replaced another LM339 and now, there's no clipping but it STILL fails the self test with OP3,4,5 etc. And now the Vtest voltage display was reading OF, despite the actual output being correct. Long story short the replacement LM339 was bad.Did most of the adjustments and now it works fine. I hope this helps someone in the future.