hybridfree/eevblog-posts huggingface dataset:
BK 2120B  Fuzzy Screen  - Page 1
Forum section: electronics / repair

author: mark_brook
author_rank: Newbie
timestamp: January 10, 2023, 05:20:47 pm
content: Hi guys I got an used Bk Presicion 2120B which seems not to adjust the focus and when i try to calibrate don't show me the usual trace,I added some pictures of the screen maybe someone can give me a hand to fix it,I got the schematics from the web but seems to be incomplete specially on adjustments procedure.I got skill on electronics but never work before with an oscilloscope and i don't wanna mess with the adjustments without knowing what to do or how to do it,Pic 1 shows a dot pushing the trigger XY push button but see the dot is not rounded its looks square,pic number 2 show not the line as usual when you set it up and pic 3 shows the way it show when I try to calibrate CH1 with 2 V p-p calibration port.I will appreciate your help by the way i got the 144 volts on P801 pin 7 and the 5 ans the 12 volts on that connector.

author: med6753
author_rank: Super Contributor
timestamp: January 11, 2023, 03:54:24 am
content: Check the resistors in the focus divider circuit. They are prone to going open.I have an older 2120 and have had it happen twice.

author: mark_brook
author_rank: Newbie
timestamp: January 11, 2023, 03:47:37 pm
content: Ok but I'm asking for the service manual for that model to verify the circuit of the focus i got one from the web for the 2120 but its an older version its more alike but seem to works ok according to that schematic
BK 2190 scope(not A, not B, not E, etc) Service info request - Page 1
Forum section: electronics / repair

author: watchmaker
author_rank: Unknown
timestamp: November 13, 2023, 08:46:03 pm
content: I took a flyer on this scope. Channel 1 works perfectly, channel 2 is highly attenuated. I switched the outputs from the channel 2 attenuator to the channel 1 vert amp and it is still highly attenuated.So I am kind of confident it is on the attenuator board. Which in this case handles both channel 1 and channel 2 attenuators.I can easily get to testpoints to follow the signal with my good scope and I would like to get this up and running. There IS a CA3127E IC for each attenuator and a couple discrete transistors. can't see for certain. Just got a pair of RCA branded ICs just in case that is where it is. Cheap enough.I thought it would be a Kenwood, but it looks like not. There is NO country of origin other than BK. Did write BK.Does anyone have any service info on this scope? I would like to know the adjustments that will be needed.Regards,Dewey

author: bdunham7
author_rank: Super Contributor
timestamp: November 13, 2023, 09:10:15 pm
content: If it is the one I'm thinking of, it is a Kikusui.I haven't reviewed these manuals, but have a look and see if they fit.

author: watchmaker
author_rank: Unknown
timestamp: November 13, 2023, 09:16:34 pm
content: Quote from: bdunham7 on November 13, 2023, 09:10:15 pmDamn. That is IT!!! Thank you.BTW, how do I contribute $$ to run this site? SEarched last week and found no clues.Regards,Dewey

author: bdunham7
author_rank: Super Contributor
timestamp: November 13, 2023, 09:36:35 pm
content: https://www.eevblog.com/donations/Or you can buy something from the EEVBlog store or an EEVBlog multimeter from Amazon.

author: watchmaker
author_rank: Unknown
timestamp: November 13, 2023, 10:03:07 pm
content: Quote from: bdunham7 on November 13, 2023, 09:36:35 pmJust did. Thanks for this forum.Regards,Dewey
B&K 2650 SPECTRUM ANALYSER HELP NEEDED - Page 1
Forum section: electronics / repair

author: gmt1@internode.on.net
author_rank: Newbie
timestamp: November 14, 2023, 05:28:25 am
content: Hi Everyone,I Have one of these handy little battery powered Specys that refuses to boot.I don't want to throw it away if possibleDoes anyone know anything about this unit ??Dare I ask, has anyone a service manual ?Any Help greatly appreciatedRegardsGeorge (Sydney, Australia)

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: November 14, 2023, 08:37:26 pm
content: After some digging, I found this website:https://bk-2650-spectrum-analyzer-service-manual.peatix.com/It says it has a service manual but when I press download it redirects me to a ru domain website with an odd 2nd level domain. It wouldn't open for me but you can try WITH CAUTION.Maybe because of my location the website won't load? Who knows. I could have accidentally pasted a virus website here.

author: gmt1@internode.on.net
author_rank: Newbie
timestamp: November 14, 2023, 11:22:42 pm
content: Hi,Yes my Virus checker flags it as containing virus so i am scared to give it a tryThanks for respondingThese 2650 are actually made by a Japanese firm but I can't remember any detailsNot looking good for repairsCheers

author: seronday
author_rank: Regular Contributor
timestamp: November 15, 2023, 12:25:12 am
content: It looks a Micronix MSA300 series.https://micronix-jp.com/english/products/spectrum-analyzer/msa300/msa338.htmlRegards.
B&K 283 digital multimeter restoration help - Page 1
Forum section: electronics / repair

author: stellarsoundlabs
author_rank: Newbie
timestamp: November 23, 2021, 02:11:43 am
content: Greetings, I'm restoring this bench multimeter. It uses some kind of a combination 3AG fuse holder - banana jack (for the negative probe lead). BK part#380-247-9-001 for each half (2 required).This one is missing the cap so I'm not even sure what it looks like. I haven't found anything at all relevant by searching online. If anyone has a name or even better, a source for such an animal, I would be most appreciative. I love keeping old gear alive! TIA
BK 3011 repair - Page 1
Forum section: electronics / repair

author: manicdoc
author_rank: Unknown
timestamp: September 11, 2022, 03:55:13 am
content: Got a BK 3011 off Ebay for a song. Turns out the output driver circuit had two dead transistors pretending to be diodes across the +/- 22v lines via two 47 ohm 1w resistors, things had got so toasty one resistor literally unsoldered itself...Checked everything in that part of the circuit, and all the other semis measure good, I'll go back one more level and check the transistors doing feedback control. I reckon either someone spiked the output or something went wrong further back...I've already recaped it for good measure, and nothing nasty was found. Got the replacement transistors on order, should be with me within a week.

author: Vincent
author_rank: Regular Contributor
timestamp: September 13, 2022, 01:36:10 am
content: Indeed quite possible that other components failed beyond the output transistors.There seems to be ICs as well? I would also check those and see if they work as expected.

author: manicdoc
author_rank: Unknown
timestamp: September 13, 2022, 05:29:48 am
content: Quote from: Vincent on September 13, 2022, 01:36:10 amA lot of it is analog, I'll double-check the signal paths.

author: manicdoc
author_rank: Unknown
timestamp: September 23, 2022, 09:06:48 am
content: Quote from: manicdoc on September 13, 2022, 05:29:48 amReplacement transistors finally arrived. I checked back the signal path 3 levels deep on transistors, nothing else bad...Decided to power up via an inline lamp and measure the voltage drops across the 46-ohm resistors that were overheating before with the bad transistors. Max measured drop seen was 0.4v which works out to be a small fraction of a watt, so well within limits.I'll power it for 10 minutes and monitor - if nothing runs away, I'll move on to confirming output behavior and then check calibration.To me, it looks like the output got zapped and the two driving transistors died as a result or might be old age...

author: manicdoc
author_rank: Unknown
timestamp: September 26, 2022, 11:06:30 pm
content: Further update, I think there is a fault in the middle of the output stage, not the final drivers. Can't get rid of a negative offset on the output and it's not amping right.I'll remove all the transistors (7) and then check each circuit fragment left and then swap out the old transistors. They are jellybean and cheap.In prep for diving in deeper, I've cleaned off all the flux, it was literally soaked in it.Slow going atm, other jobs to do.
BK 308 Insulation Tester - design error? - Page 1
Forum section: electronics / repair

author: Paul Moir
author_rank: Frequent Contributor
timestamp: October 14, 2019, 05:21:40 pm
content: Recently I purchased an old BK Precision 308 insulation tester. I only seldom need a megger so could never justify the price of a new one. While checking it out, I ran into a bit of an unusual problem: while it measured correctly on all ranges, the 250V range was only putting out 187V. BK Precision was kind enough to furnish a schematic upon request, and after tracing it through I found the failure was a partial short in deadtime control pin of the TL594, which is a fancy TL494 PWM controller. The TL594 is used to generate the high voltage for the 250/500/1000V ranges.The 308 had been repaired before and while the schematic calls for a TL594, a TL494 is present which makes me suspect that it was replaced before.Having a look at the schematic, I think I spotted the cause of the failure. This section of the range switch does two things: first it sets the reference for the voltage error amp via R1, R2 and Three_Rs. Second it modifies the PWM dead time via R3. The capacitor shunted across R3 I think must be to temporarily shut down the PWM when switching ranges. However I think it generates a negative pulse to the TL594 when VREF when the meter is powered off, the worst being in the middle range. Normally this pin provides 2-10uA current, and instead mine's consuming ~500uA.What do you think, is this a mistake or is 4.7uF transitioning from 5v to 0v not really enough to damage anything? I was thinking about shunting the pin with a schottky.
BK 4040 Ext. Counter Repair - Page 1
Forum section: electronics / repair

author: watchmaker
author_rank: Unknown
timestamp: September 30, 2023, 08:05:30 pm
content: BK Precision 4040 schematic 1.pdf(930.65 kB - downloaded 59 times.)My 4040 does great as a frequency generator.However, there is an issue with the external counter function. Square wave counts match my Siglent scope. Triangle and sine waves are all over the map.I pulled the schematic from BAMA, attached.It looks to me like there are only two things differnt between the external input and the internal frequency counter. One is U117B which is an 74L500. The other is a 10K resistor, R210.When I open it the first thing I will check is the value of that resistor. If not it looks like I should replace the NAND gate.Do you see anything else?Regards,Dewey

author: floobydust
author_rank: Super Contributor
timestamp: September 30, 2023, 08:38:45 pm
content: U117 is switching in either the internal or external signal to the freq. counter. So on EXT it will naturally pickup noise and not read the generator signal, aside from using the timebase.I think EXT selects the analog front end (JFET Q108, Q109, U116 etc.) to U117A. I would check signal and DC voltages in that subcircuit if it is not working. Check C136 47uF has the right polarity, if the JFET pre-amp has failed it might go reverse.J115 not sure where it goes but must be to EXT BNC.

author: watchmaker
author_rank: Unknown
timestamp: September 30, 2023, 08:51:44 pm
content: Quote from: floobydust on September 30, 2023, 08:38:45 pmThank you. Will follow up when I do the deed.Regards,Dewey

author: watchmaker
author_rank: Unknown
timestamp: October 01, 2023, 03:20:07 pm
content: Decided to trace it starting from the source. Turns out it was the cable at the BNC connector. The pin is too short/small. It does need calibration though. Can be 10% off below 2500Hz on other than square wave.But w/ the scope it is not worth sending out for calibration. Will look and see if there is anything, but I did not see any trimmers for the IC. So that may be up next after all.Still need to look at all the pins on the LS00 and check the resistor.I can always measure the sq wave from a generator and presume the freq is stable on other waveforms, but what fun is that. In fact, not sure why this matters at all to me.Just me being OCD.Regards,Dewey
B&K Precision 4040 function generator issues - Page 1
Forum section: electronics / repair

author: prodman
author_rank: Newbie
timestamp: January 12, 2021, 09:03:03 pm
content: I have acquired a B&K Precision model 4040 function/sweep generator with "issues". Does anyone know where I can find a service manual and/or schematic so that I can take a crack at fixing it?

author: bdunham7
author_rank: Super Contributor
timestamp: January 12, 2021, 09:08:52 pm
content: Quote from: prodman on January 12, 2021, 09:03:03 pmemail BK Precision, they're pretty good about information for their older stuff.

author: floobydust
author_rank: Super Contributor
timestamp: January 12, 2021, 11:01:05 pm
content: These are actually pretty good. Got a 4011 out of the garbage and it looks like they just stack more boards inside for more features.Common problem is blown output transistors. If you get a stuck DC offset or distorted waveforms, I would look there.

author: prodman
author_rank: Newbie
timestamp: January 13, 2021, 12:39:41 am
content: Thanks for the suggestions. BK Precision just sent me the schematic and parts list for the 4040, so I'm happy. The main issue is distorted output on some ranges, so I will check the output drivers.

author: floobydust
author_rank: Super Contributor
timestamp: January 13, 2021, 12:45:32 am
content: Can you submit the schematic etc. toThe Boat Anchor Manual Archive BAMAThey have a lot of service manuals there, but are not indexed by the big search engines so their manuals are hidden.
B&K  650 tube tester - need replacement meter - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: October 01, 2022, 11:00:03 pm
content: Does anyone know the specs for the meter used in the B&k 650 tube tester? I am looking to replace it with a similar meter and I can't find out the resistance of the coil or the full scale current. I can't find any markings on the meter.The meter was damaged when I purchased it as-is. Upon testing the meter with a 10K ohm resistor in series with a power supply, the pointer started to move with about 10v and did not reach full scale with the limit of my power supply at 33v. This voltage seemed too high for this meter.

author: floobydust
author_rank: Super Contributor
timestamp: October 02, 2022, 12:41:19 am
content: Is this in-circuit with the antique capacitor C4 200uF 6V across the meter? I'd expect that cap to be defective, along with every other electrolytic given their age.It would be strange to have such a high full-scale current, you seem to be around 3mA. The 6AT6 is rated 1mA max. plate current, so the meter movement seems off.There are some mods to limit pegging the panel meter hard, hopefully it is not damaged. Try a much smaller series resistor say 1k with your power supply and closely watch the meter movement, for sticking, or linearity if 1/2 scale is 1/2 the full-scale current if you can get there. You can measure the panel meter ohms as well.I have seen contamination inside (metal chips) cause problems as well. Had to do surgery and use masking tape to pick up everything stuck to the magnet inside, of panel meters.Check closely the meter faceplate for any text about the meter movement. It might match other B&K tube testers but just have a different faceplate.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: October 02, 2022, 03:24:54 pm
content: Thank you for your reply.I can not find any markings on the meter face indicating the meter movement specs. (see photo).The meter was damaged when I received it. The pointer would not move. I got the pointer to move freely but it would not measure any current. After checking the solder connections on the spring, the meter would move with current applied although it took too much current to move it half-way. I will try your suggestion with a 1k resistor. Usually these meters are 100ua or a little more.

author: richnormand
author_rank: Unknown
timestamp: October 02, 2022, 07:42:23 pm
content: Different model from B&K but the meter has a cap across it and a rating of 1mA with a resistance of 100 ohm.http://www.tubebooks.org/Books/Atwood/B&K%20Model%20747%20Dyna-Jet%20Tube%20Tester%20Schematic.pdfMight give you something to start from.Model 650 manual with calibration and schematics. Unfortunately there are no details on the meter itself.http://bee.mif.pg.gda.pl/ciasteczkowypotwor/B&K/BK650%20Cal.pdfAt a minimum make sure the cap is not shorted.....
B&K Dyna-Quik 500 Tube Tester E-cap - Page 1
Forum section: electronics / repair

author: RossH0755
author_rank: Newbie
timestamp: December 28, 2021, 05:37:59 pm
content: I have a Dyna-Quik 500, Type 83 tube version that according to the manual has an aluminum 250uF 6V cap on the meter. There are no markings on it, so I can't look it up for other specs. Is there a reason I might not want to replace that one with a general-purpose series E-cap of those values or higher voltage?Thanks,Ross

author: floobydust
author_rank: Super Contributor
timestamp: December 28, 2021, 07:03:46 pm
content: I would say round to the nearest EIA value like 220uF or 270uF at 16V or 25V for a replacement electrolytic capacitor.We don't know what the panel meter is - if it has a resistor (voltmeter) or raw uA ammeter. Usually there would be some clamp diodes to protect it.Manual I found herehttp://jogis-roehrenbude.de/Roehren-Geschichtliches/Roe-Pruefer/B&K-500/bk500_manual.pdf

author: RossH0755
author_rank: Newbie
timestamp: December 29, 2021, 12:49:05 am
content: Those were my thoughts on the caps. I just needed to run it past others.Thank you.
BK Precision 1465 Help with Repair - Page 1
Forum section: electronics / repair

author: Ernest1
author_rank: Contributor
timestamp: March 16, 2020, 03:08:34 am
content: So I just got this oscilloscope a few days ago and initially it didn't have a horizontal line on the screen but it was displaying off to the left like in pic 1 and I fixed that by messing with the break out board thingy at the back of the crt in pic 2. I tested it out a bit after wards and decided to clean it since it was working well.I took apart and cleaned the front panel and all the knobs separately with alcohol electronics cleaner and Windex for the screen.This is where I think I broke it, I sprayed the bottom of the bottom board pic 3 and pic 4 with electronics cleaner and used a tooth brush to clean the dust off but while I was doing that I heard something hit the floor and I found this little solder nugget pic 5, pic 6 with dimensions L 3.5mm W 1.2mm and I thought nothing off it. When I turned on the oscilloscope the screen lit up but there was no line and I turned the knobs and the DC BAL pot I can see the screen the screen brightens move up and down or left to right as if there was a line but the size of the screen and very dim. I tried to find where it fell from and found a likely spot but it didn't change anything after jumping the traces, I also tested the resistance and voltage before hand to make sure doing that doesn't blow it up. I have no idea how these oscilloscopes work internally so im reading a guide on fixing oscilloscopes from this forum but in the mean time if anyone has any suggestions or knows what the issue is please let me know im really sad right now
BK Precision 1479B Oscilloscope Service Manual? - Page 1
Forum section: electronics / repair

author: Axtman
author_rank: Regular Contributor
timestamp: April 06, 2019, 03:54:51 am
content: I am looking for a BK Precision 1479B Oscilloscope Service Manual. Does anyone have a scan or know where I can get one free? Thanks.

author: tautech
author_rank: Super Contributor
timestamp: April 06, 2019, 04:32:02 am
content: Had a very quick look for one and got 2 hits that pointed to the same source:https://www.eevblog.com/forum/repair/bk-precision-1479b-vertical-amp-problem/

author: Axtman
author_rank: Regular Contributor
timestamp: April 06, 2019, 11:41:35 pm
content: Great! Thanks!

author: adrianblack
author_rank: Contributor
timestamp: September 01, 2022, 05:04:09 pm
content: I know this is old, but in case this is still helpful or helpful to anyone else, I had these manuals and just scanned them:Service manual: (for 1474, 1479, 1479A and 1479B)https://archive.org/details/bk-precision-1474-1479-1479-a-and-1479-b-service-manualUser manual: (for 1497B)https://archive.org/details/bk-precision-1479-b-dual-trace-oscilloscope-instruction-manualParts list: (for 1497B)https://archive.org/details/bk-precision-1479-b-schematics-parts-list-and-schematic

author: fordem
author_rank: Regular Contributor
timestamp: September 02, 2022, 02:45:29 am
content: You can also just ask BK, if they have it, they'll give you a pdf copy - I've asked and gotten documentation on a couple of different occassions.
BK Precision 1550 Power Supply Repair after Reverse Polarity - Page 1
Forum section: electronics / repair

author: SparkSmokeMan
author_rank: Newbie
timestamp: September 25, 2024, 09:06:32 pm
content: Hi All,I accidentally hooked my trusty old 1550 up backward to a 12V lead acid battery.At first, it appeared that the supply survived, however I started noticing some symptoms.-The unit turns on, all buttons and display work.-Sometimes, the unit works normally, especially at low voltages and currents-After a few minutes, the output stops creating current, and I cant measure any voltage with my multimeter. The unit needs to be turned off and turned back on and sometimes it begins working again. Sometimes, it will continue to produce current, but only a fraction of what it should be outputting.Troubleshooting:-I first checked the main board and front panel board for damaged components and burn marks. None found. There was no smoke or sound when I accidentally reversed the polarity.-I checked the MOSFETS for shorts, and they all appear to test correctly-I obtained the schematic for this unit, but am unsure what to check nextDo you have any advice for next troubleshootign steps? I'd hate to thow this out when it appears to be about 75% functional. Any help would be appreciated.

author: bostonman
author_rank: Super Contributor
timestamp: September 26, 2024, 02:56:38 am
content: Can you post the schematics?

author: SparkSmokeMan
author_rank: Newbie
timestamp: September 26, 2024, 09:16:46 pm
content: Sure thing! Please see attached:

author: bostonman
author_rank: Super Contributor
timestamp: September 27, 2024, 02:58:01 am
content: Sure you have the entire schematic? I don't see where ON/OFF goes (next to PC5 on the right side of the schematic).Since you claim it tends to work, I'm thinking maybe something happened to U5. It's a D Flop and I'm assuming SW2 is sort of reset because the power switch is SW1 on top.Some stuff doesn't make sense such as: what is SW2-A (I don't see where it goes), what is M2 and M3, and ZD4 is also labeled 10k. This is why I'm wondering if you're missing a page.I'd start with the obvious, the 9V and Vcc. From what it looks, the output is isolated from the input through the opto.Measuring the 9V and Vcc will at least eliminate or isolate (if it's not measuring correctly) the entire upper half of the circuit.
bk precision 1550 repair - Page 1
Forum section: electronics / repair

author: saibot1988
author_rank: Newbie
timestamp: August 23, 2022, 07:24:20 pm
content: Hello guys,today I killed my power supply bk precision 1550.I made a unwanted connection between Postive (voltage was set to 3v3) and the Ground of the USB Port.After I big bang and lot of smoke I opened the supply and found a exploded Transistor Q11 (MPSA44) and a completely burned resistor R63.I tested also the Transistor Q12 (2SA950) and came to the result that Q12 is defective too...I can power on the supply, but it shows CC at the lcd and it is not possible to adjust the voltag.Does someone have a service manual of this power supply or know the value of the burned resistor R63?R. I. P my loved compact Power Supply

author: MikeK
author_rank: Super Contributor
timestamp: August 23, 2022, 08:39:17 pm
content: Did you ask BK nicely?

author: saibot1988
author_rank: Newbie
timestamp: August 23, 2022, 09:00:55 pm
content: Yes, but till now I don't got a feedback.I found that this power supply is equal with with following models.TENMA 72-8345MANSON NSP-3630Voltcraft LSP 1363For the Voltcraft I found a schematichttps://asset.conrad.com/media10/add/160267/c1/-/en/000515266CD01/circuit-diagramm-515266-voltcraft-lsp-1363-bench-psu-adjustable-voltage-1-36-v-dc-015-3-a-100-w-no-of-outputs-1-x.pdfhttps://www.eevblog.com/forum/testgear/bk-1550-based-on-same-design-as-tenma-72-8345-and-manson-nsp-3630/https://www.eevblog.com/forum/repair/voltcraft-lsp-1363-power-supply-no-output/

author: saibot1988
author_rank: Newbie
timestamp: August 28, 2022, 08:09:39 am
content: After replacing the two Transistors and the burned Resistor the Power Supply is working again
B&K Precision 1651 PSU adjustment - Page 1
Forum section: electronics / repair

author: beowulfenator
author_rank: Contributor
timestamp: May 12, 2021, 09:29:54 pm
content: I have bought this used PSU from ebay and did the calibration as it is described in the documentation. It went through fine, but I can't help but wonder why the range of their adjustment potentiometers is so big? For example, on the adjustable channels the zero needs to be set within 20 millivolts, but the overall range of the adjustment pot is several volts. Because of this, even a tiny nudge of the pot causes the value to change by tens of millivolts.The pots are in series with a constant resistance, for example a 4.7K pot in series with a 1.5K resistor. Why is it designed this way (and not a bigger constant resistor and smaller adjustable resistor)? Why make the pot so big and so adjustable, when it seems to only make it harder to adjust?

author: Alex_Baker
author_rank: Frequent Contributor
timestamp: May 14, 2021, 06:21:36 pm
content: Surprised nobody has responded to this thread yet,I am not very experienced in electronics but I have a thought, the potentiometer (SVR9?) looks like it is a part of a relatively complex resistor divider network connected to that op-amp, by changing the two resistor values like you mentioned you would be changing the whole system, its not as simple as the tow resistors adding together. in other words, when you turn that pot you are not changing resistance you are changing voltage (as far as the op-amp is concerned), and by changing their values you affect the range of voltage that the pot can output to the op-amp.That's my guess, They probably could have made it easier to adjust but ultimately they most likely wanted something simple and cost effective.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 14, 2021, 09:20:18 pm
content: The circuit looks rather old and a bit odd. When adjusting the full scale range this would also effect the zero setting. So the adjustment range for the zero needs to be quite large to allow for the different full scale voltage settungs. The resistors in the old time also had quite some tolerance, especially the resistance of the pots that can enter in the circuit.So the circuit is just not the best, but probably just good enough. It was a complicated task to change a board - so don't fix it if you don't have too.They may have started with a 20 trurns trimmer and only later changes to a simple one for cost cutting.
BK Precision 1652 PSU Voltage Issues - Page 1
Forum section: electronics / repair

author: deezick
author_rank: Newbie
timestamp: November 23, 2019, 04:53:32 pm
content: Hello, I am having some issues with my bk precision 1652 0-24 volt triple output power supply. It seems that channel A only goes up to 20.5 volts and channel B goes up to 21.5 volts, when each should go up to 24 volts. I have double checked that the correct output is being displayed with my multimeter and it reads just about spot on. I think I narrowed the issue down to one location on the board that has some carbonization. It's four zener diodes and two 220 ohm resistors. I was wondering if this could be the voltage output issue for both channels or is it a red herring and I should look elsewhere? I would like to know and test as much as possible before I order the replacement parts from digikey as the shipping costs more than the components.Here is what I have measured, zeners are from left to right.Image of the area in question:https://imgur.com/gallery/ifIVWJFLeft resistor 218.5 ohms, right resistor 219 ohms. Both within spec.Zener 1 (D21 )Anode to cathode resistance: 12.55 mega ohmsCathode to anode resistance: 12.89 mega ohmsZener 2 (D22)Anode to cathode resistance: 12.66 mega ohmsCathode to anode resistance: 12.48 mega ohmsZener 3 (D20)Anode to cathode resistance: 13.63 mega ohmsCathode to anode resistance: 12.03 mega ohmsZener 4 (D22)Anode to cathode resistance: 11.91 mega ohmsCathode to anode resistance: 13.61 mega ohmsI can provide more information as necessary, the board is sitting right next to me.

author: deezick
author_rank: Newbie
timestamp: November 26, 2019, 12:49:54 am
content: bump - Ordered the diodes, let's hope that's the only issue. Once I replace them I'll go around checking regulators.
BK Precision 1655A AC Power Suppy- Replacement Brush and Leakage Probe Fuse Info - Page 1
Forum section: electronics / repair

author: t1d
author_rank: Super Contributor
timestamp: March 06, 2021, 01:58:40 am
content: BK Precision has instructions in the manual for how to change the brush. However, they do not list the part in the BOM and they do not sell the individual brush. They want to sell you the whole coil assembly. They could not tell me where to get the brush.I bumped across this listing for a brush that might fit... Staco Energy #146-0121-S. I found it at this seller:https://www.galco.com/buy/Staco-Energy/146-0121-SAt $48, its not cheap. But, that's still cheaper than Ebay and Amazon.Interestingly, I did not find a listing for the part on the Staco site.I think this shape of brush is called a "Tbird."Edit: The Leakage Probe Fuse is a 500mA/1KV, Ceramic, 1/4" x 1-1/4" Safety Fuse. It is not listed in the BOM, either.I bought this unit new. The first was defective right out of the box. Its replacement was the same. So, I returned it. Meaning, I can not help with any additional details.I hope the information helps someone.
BK Precision 1735 power supply - Page 1
Forum section: electronics / repair

author: EK701
author_rank: Contributor
timestamp: November 21, 2014, 02:28:39 am
content: I just got a BK Precision 1735 (not the 1735A) power supply (http://www.tequipment.net/BK1735.html) for cheap and I want to do some basic tests on it before I plug it in, so I'm looking for a service manual. I did a web search, but no luck. I can probably get by without one, but it's always better to have the manual. If anyone knows where to get the manual online or if you have a hard copy, please let me know.Thanks!Eric

author: matt6ft9
author_rank: Contributor
timestamp: November 29, 2014, 02:02:17 am
content: 'repaired one of those a couple of months ago. It had a bad bridge rectifier.I was not able to find a service manual either. But, on the bright side, the power supply was based around the LM723 voltage regulator.www.ti.com/lit/ds/symlink/lm723.pdfIt's not too complicated of a circuit.

author: t1d
author_rank: Super Contributor
timestamp: May 16, 2019, 10:56:03 am
content: Repair videos. Schematic and pix links in comments of first video. I am not the author. Good stuff.Schematic Attached. Board pix too big to attach; see first video comments for link.https://drive.google.com/file/d/1hPfrbPpVYsPpvWJyk9woXMio2SEN9Y1b/viewhttps://drive.google.com/file/d/1UTZf0lRMxIFOBGM3m2JKutHKFZUPHFZg/viewhttps://drive.google.com/file/d/1jZkXvO7JUSCr2tn8F2lbwndxn316j08r/viewYes, I know this is an old thread, but this post keeps the information centralized.
B&K Precision 1760A PS info - Page 1
Forum section: electronics / repair

author: tryingtolearn
author_rank: Contributor
timestamp: March 15, 2025, 09:22:51 pm
content: Does anyone have a good reputable link to get a schematic for a B&K Precision 1760A DC Power Supply?Not looking for a freebie - will purchase.Thanks for any info.

author: tryingtolearn
author_rank: Contributor
timestamp: March 16, 2025, 02:34:06 am
content: in case anyone is searching for the same or different models -http://bama.edebris.com/manuals/b&k/

author: Swake
author_rank: Frequent Contributor
timestamp: March 16, 2025, 08:46:43 pm
content: Is the 1760A version so much different from the 1760, I know the enclosure has evolved but does the electronics too?

author: tryingtolearn
author_rank: Contributor
timestamp: March 17, 2025, 09:03:31 am
content: Slight differences but in the ballpark.Im still waiting on a response from B&K support for the actual schematic - I heard if you contact them they will let you know about purchasing options for some schematics - so far that isnt the case hahaha

author: tom66
author_rank: Super Contributor
timestamp: March 17, 2025, 02:15:14 pm
content: B&K doesn't make the majority of their own kit (if any of it!) They rebadge stuff. You'd be better off trying to figure out the OEM and contacting them. If it's a Chinese OEM then you're probably out of luck unless someone has reverse engineered it, they aren't all that keen to share schematics because the concept of design copyright isn't really well enforced there.

author: tryingtolearn
author_rank: Contributor
timestamp: March 17, 2025, 02:24:27 pm
content: Yeah not holding my breath to get a response. Its just a curb find that someone obviously destroyed a few internals trying to "Fix" something. Itll be put on the todo bench until something turns up.

author: tryingtolearn
author_rank: Contributor
timestamp: March 17, 2025, 05:46:15 pm
content: Well B&K responded and sent the service manual for the 1760 said that is all they have for the 1760a.. oh well
BK Precision 1762 power supply Voltage adjustments - Page 1
Forum section: electronics / repair

author: patrick richardson
author_rank: Newbie
timestamp: May 18, 2023, 04:44:35 pm
content: I've got a BK Precision 1762 power supply. If you've used one, the coarse adjust is way too coarse and the fine adjust is way too fine. A multiturn coarse adjustment would have been nice...I increased the resistor in parallel with the fine adjust pot R68 from 2.7k to 4.7k and it gives a little more range on the fine adjust, but starts being nonlinear at the upper end. Going higher than 4.7k gets too non-linear. I can't find schematics (i asked BK and done searches) or a tech manual.It looks like the board mount control pots are 25k, so replacing them with a multi-turn isn't likely.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 18, 2023, 09:47:54 pm
content: if the main pots are 25k, its not a problem to find ones, sure theyll cost a bit, but youll get the control you need, ive done the same thing on my kepco ate psu 1 pot for Volts 1pot for Current no fine
BK Precision 1770 linear power supply instruction and service manuals - Page 1
Forum section: electronics / repair

author: disago
author_rank: Newbie
timestamp: May 16, 2024, 01:42:33 am
content: Hi all,I just acquired a BK Precision 1770 linear power supply and had some trouble obtaining the Service Manual. I requested it from BK Precision support and they replied the same day with it.I'm attaching it in case it's useful for anyone else, along with the User Manual and the Datasheet.Have a great week!

author: MathWizard
author_rank: Super Contributor
timestamp: May 18, 2024, 07:03:12 am
content: Thanks, just looking at the schematic on page 9 of the SM, they have the outputs of 3 op-amps tied directly together, U103/104. How's that allowable, is it a mistake on the schematic ??Also, I'm just trying to make up some values and get the circuit working, but whats the purpose of Q105 on that page ?? C155 would start at zero volts, and then if Q105 turns on, it would keep it there, so to me that doesn't seem like a soft start type setup. Is it some overvoltage sensing of the +20V Vcc with that zener ??

author: Kleinstein
author_rank: Super Contributor
timestamp: May 18, 2024, 08:39:35 am
content: The amplifiers that are tied together at the outputs are Lm393. This are not OP-amps, but comparators with a open collector ouput.With some care a few of the comparators can be used for linear operation too, but they are prone to oscillation and the manufacturer / age may matter.
BK Precision 1803D Frequency Counter  prescaler - Page 1
Forum section: electronics / repair

author: rfengg
author_rank: Regular Contributor
timestamp: November 12, 2024, 03:21:19 pm
content: Hi All,I have a BK Precision 1803D Frequency Counter which has 2 inputs, HF (10Hz to 20MHz) and VHF (10MHz to 200MHz) .It looks like the prescaler for the VHF band which is a chip marked as UPB-467 has failed with no output.....for the life of me, I can't seem to get any info on this chip on the web.Does anyone have more info on this chip? Or is there anyway to determine what the prescaling factor could be as then I could find another chip to do the same?

author: factory
author_rank: Super Contributor
timestamp: November 12, 2024, 04:03:54 pm
content: This might be quite recent, datasheet & manual are dated 2014, the BK website states this model was discontinued in Jan 2023.David

author: George Edmonds
author_rank: Frequent Contributor
timestamp: November 12, 2024, 05:12:41 pm
content: Look at Plessey SP8695A.G Edmonds

author: coromonadalix
author_rank: Super Contributor
timestamp: November 12, 2024, 05:35:40 pm
content: http://www.bitsavers.org/components/plessey/1988_Plessey_Frequency_Dividers_and_Synthesisers_IC_Handbook.pdf

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: November 12, 2024, 07:48:36 pm
content: Hello rfengg,It seems that there's asecond sourcefrom Fujitsu : MB467.Check the pinout to confirm equivalence (please report).Ask for quotehere.If too difficult to procure, try to cobble something with anMC12080

author: rfengg
author_rank: Regular Contributor
timestamp: November 13, 2024, 03:20:50 pm
content: Thank you all for your replies.....@timeandfrequency : You have nailed it partner......the MB467 seems like an exact replacement for the UPB-467.I traced the UPB-467 nodes on the BK Precision 1803D and compared it to the datasheet of the MB467 and it seems to be like a 1:1 match.Kudos man....keep up the good work......now I only need to worry about trying to get hold of one
B&K Precision 2125 Oscilloscope Vertical Shift - Page 1
Forum section: electronics / repair

author: rsaxvc
author_rank: Contributor
timestamp: March 14, 2022, 03:58:34 am
content: About a year ago I picked up quite a bit of test equipment, including several dual-trace analog oscilloscopes, a few of which have this issue where the vertical channel shifts up and down for a bit. It doesn't happen reliably, but often happens for a couple minutes on and off. Unless I'm monitoring something - then it works fine.I've got a short video of it here:It affects both channels similarly, independent of the vertical scale - I think this means that the problem is either after the preamps in the vertical amp or in something that affects both preamps similarly like a power supply. I figured I'd ask if anyone had seem something similar or might have some direction on where I should look next.Todo/ideas:check XY mode to see if it affects horizontal ampcheck low/mid voltage power supplies with a scope - nothing interesting with a DMM

author: bdunham7
author_rank: Super Contributor
timestamp: March 14, 2022, 05:08:46 am
content: I'd take the cover off and try carefully wiggling all the various inter-board connections, jumpers and grounds to see if something is a bit loose.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: March 14, 2022, 04:47:05 pm
content: I second the cleaning of connections and cleaning the pots and inputs.Maybe even a bad solder joint.

author: med6753
author_rank: Super Contributor
timestamp: March 16, 2022, 07:16:22 am
content: If you checked the PSU voltages and they are OK then concentrate on an issue in the vertical amplifier. That's vertical shift, not horizontal shift.
BK Precision 2190a - Page 1
Forum section: electronics / repair

author: steven2605
author_rank: Newbie
timestamp: January 08, 2023, 01:33:47 am
content: Have a pair of BK 2190A's. One is in really nice shape and does not power-up (of course!). The other is a bit noisy, way of calibration, but functions. My search for manuals, etc., comes up nothing. Any input anyone?

author: coromonadalix
author_rank: Super Contributor
timestamp: January 08, 2023, 02:09:40 am
content: https://www.badcaps.net/forum/showthread.php?t=57677for the 2190 not the "A" but should have some similarities ?

author: bdunham7
author_rank: Super Contributor
timestamp: January 08, 2023, 02:17:47 am
content: They look Hitachi-like, but I can't find a matching model. The operators instruction manual is readily available, but no service manual pops up. You could contact BK and if they have the manual they'll send you a copy.

author: rcr66
author_rank: Newbie
timestamp: January 18, 2024, 02:41:07 am
content: If you're still needing them, here are the instruction and service manuals for the 2190A, direct from BK Precision
B&K precision 2190E - Page 1
Forum section: electronics / repair

author: alfa3615
author_rank: Newbie
timestamp: August 26, 2021, 12:50:31 am
content: Hi allMy scope B&K precision 2190E stuck in boot screen !any helpThanks advance

author: alfa3615
author_rank: Newbie
timestamp: September 05, 2021, 01:35:36 pm
content: Fixed !Thanks to tauteck

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 05, 2021, 02:05:41 pm
content: So you fixed it, and goodbye?At least post how you fixed it, don't be an ***, there might be more people with your same problem.

author: alfa3615
author_rank: Newbie
timestamp: September 05, 2021, 10:30:43 pm
content: For all the guys who have the same problem as metry this. if it doesn't work, find "tauteck" it will help youhttps://bkpmedia.s3-us-west-1.amazonaws.com/external/2190E_recovery_by_USB_driver.zip

author: jetusenet
author_rank: Newbie
timestamp: January 31, 2022, 03:38:59 pm
content: Thank you very much for posting that .zipWoke up to a non-working scope and this post saved me!Thanks againJeff

author: rocketsfolly
author_rank: Newbie
timestamp: February 21, 2022, 09:06:30 am
content: cant find this "tauteck" whatever it is, downloaded the zip file and couldbt get it to work, do i need to make a bootable usb with it?thank you !

author: rocketsfolly
author_rank: Newbie
timestamp: February 21, 2022, 09:51:44 am
content: nevermind. got mad and threw it out the damn window

author: tautech
author_rank: Super Contributor
timestamp: February 21, 2022, 11:13:06 am
content: Quote from: rocketsfolly on February 21, 2022, 09:06:30 amYes. Needs be 8GB max and files in the root.Quote from: rocketsfolly on February 21, 2022, 09:51:44 amShame, it's a Siglent SDS1102CNL+, a basic but reliable little DSO.

author: Carlos Zubieta
author_rank: Newbie
timestamp: January 11, 2023, 12:57:06 am
content: Thanks to your help I solved it!!Why does this error occur and how can I prevent it from occurring again?
BK Precision 3011B Repair - Page 1
Forum section: electronics / repair

author: manicdoc
author_rank: Unknown
timestamp: February 23, 2023, 09:42:33 pm
content: Just a quick write up of my repair, this was over several months as DIY was needed to be done.- R514 & R515 1w resistors were 'toast' - replaced- Replaced all electrolytics caps- Replaced Q506, Q507 output stage transistors, dead shorts - explains the toasty resistors..Then about 3 months passed..- Did some measuring around, the signals out of the generator circuitry were fine, but around Q501 the signal failed to propagate, nailed to +15v, so replaced it, and the output came backThings left to do:- Mhz range doesn't work, completely flat - probably bad connection- square wave has a slight wiggle, I'll see if I can tune it out- slightly offset output, I'll see if I can tune out- sin wave output, looks a little too sharp to my eyes, see if I can tune out

author: manicdoc
author_rank: Unknown
timestamp: February 24, 2023, 09:05:51 am
content: Update:- Mhz range, the adjustment cap just needed a tweak, works fine now- everything needed just a little tweak to get into spec. So all good now.
FOUND - BK Precision 4011 Func Gen schematic?   - Page 1
Forum section: electronics / repair

author: RogerMc
author_rank: Contributor
timestamp: December 18, 2014, 09:36:40 pm
content: I've been looking around and so far no luck.Does anyone have, or can point me in the direction of a schematic for this one?Thanks!Roger

author: RogerMc
author_rank: Contributor
timestamp: December 19, 2014, 05:38:38 pm
content: Has been found ...

author: ivan747
author_rank: Super Contributor
timestamp: December 19, 2014, 07:59:10 pm
content: Could you please attach the file so that anyone who needs it can have it? Thanks

author: RogerMc
author_rank: Contributor
timestamp: December 22, 2014, 04:51:13 pm
content: I have been given explicit permission from BK Precision to share this schematic.

author: tautech
author_rank: Super Contributor
timestamp: December 22, 2014, 10:31:50 pm
content: Nice of them.Quick upload it to one of the free download sites linked in this board for all to access.

author: ivan747
author_rank: Super Contributor
timestamp: December 23, 2014, 12:07:14 am
content: I think you can download from here without an account.

author: patrick richardson
author_rank: Newbie
timestamp: May 12, 2023, 02:19:51 pm
content: The previously posted schematics are low resolution and you can't read values. Attached please find a copy with MOST of the schematic where things are readable.I worked with B&K to get as many high resolution files that i could and then i stitched them together. I recently repaired one quickly by being able to read the values easily. Bear in mind different versions have different refdes', but the values and schematics are basically the same.B&K was very helpful and gave me permission to post this. Enjoy!
I need Bk Precision 4086AWG PCB photos - Page 1
Forum section: electronics / repair

author: Nuljaska
author_rank: Newbie
timestamp: September 27, 2019, 04:18:54 am
content: Hello everyone. Do anyone has photos of this generator PCB boards. I need photos so i can know where my off soldered components belongs. I need photos of these components spots: all of the little red resistors(total 9), all of the big capasitors(total 9), and all of the regulator type cased components on power board (total 11). I need photos where i can clearly see names of components and their spots.Thanks.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: September 27, 2019, 02:36:04 pm
content: I think there are two styles of this generator. Do you have one with LCD screen or the one with VFD?I have the one with LCD

author: Nuljaska
author_rank: Newbie
timestamp: September 27, 2019, 08:58:38 pm
content: I have that one, and i think that is the one with VFD.https://www.bkprecision.com/products/discontinued/4086AWG-80-mhz-function-arbitrary-generator.html

author: Legend18s
author_rank: Newbie
timestamp: June 19, 2025, 05:05:55 pm
content: I am repairing a standard 4086 (non-AWG) with the VF display. here are some of the photos of the PCB (Generator side and power supply side). Also if you have repaired one of these things before some help would be greatly appreciated.