hybridfree/eevblog-posts huggingface dataset:
Replacement fan for Agilent U2761a - Page 1
Forum section: electronics / repair

author: JJalling
author_rank: Unknown
timestamp: March 25, 2018, 05:49:26 pm
content: Hello all,I have a Agilent U2761a Function generator with a bad fan - one of the bearings sounds broken. It's a 20x20x8mm 12V fan from Sunon (P/N: GM1201PDV1-8). Does anyone know where I can find a replacement? My google foo is failing me on this one - I'm only finding 5V versions.BR Jonas
Identify SMD chip (SOT-23-6) "7A50a" - Page 1
Forum section: electronics / repair

author: technogeeky
author_rank: Frequent Contributor
timestamp: March 24, 2018, 06:27:15 am
content: Hello,I accidentally broke (at least) this chip on a small wind/temperature/433MHz sensor module (though the power consumption was horrid before I broke it).As far as I can tell, the package isSOT-23-6.The VCC comes from two D battery cells, soVCC_maxis going to be 3.0 volts or so. It seems to stop functioning at around 1.85 volts, soVCC_minis somewhere around 1.85 volts.The part number is7A50a.The part is connected directly to the battery via pin6.The part is connected to the battery through an inductor via pin5.Pin4is used by the micro (labeledCLCK1).Pin3is a test point.Pin2is connected directly to ground.Pin1is connected to a "J26.000" (26 MHz) crystal oscillator.

author: stj
author_rank: Super Contributor
timestamp: March 24, 2018, 11:54:23 am
content: the only "7A" reference in my databook is this:

author: technogeeky
author_rank: Frequent Contributor
timestamp: March 24, 2018, 07:06:12 pm
content: Quote from: stj on March 24, 2018, 11:54:23 amThanks for the attempt. I don't think that can be it. I don't know how two transistors would work in that situation (though I'm not sure what is going on anyway).Plus, that package is too large, I think.

author: amyk
author_rank: Super Contributor
timestamp: March 25, 2018, 03:13:16 am
content: CMT2117A.

author: technogeeky
author_rank: Frequent Contributor
timestamp: March 25, 2018, 06:05:34 am
content: Quote from: amyk on March 25, 2018, 03:13:16 amThat looks perfect! Thanks very much. Can I ask what tools or resources you used, or doth the magician keep his secrets hidden up his sleeve?

author: BravoV
author_rank: Super Contributor
timestamp: March 25, 2018, 06:15:08 am
content: Quote from: technogeeky on March 25, 2018, 06:05:34 amAmyk does have magnificent magic on identifying SMD components.Helped me ->HEREtoo while ago, and on many other occasions here.

author: amyk
author_rank: Super Contributor
timestamp: March 25, 2018, 05:26:15 pm
content: Just Googled it... the 26MHz oscillator connection seems distinctive so I searched "sot23-6 7A 26MHz" and found CMT2119A, which seemed close enough but from its marking scheme (9Axxx) guessed CMT2117Aand it was the exact match.
Keithley 2000 repair; display PCB damage - Page 1
Forum section: electronics / repair

author: voltampere
author_rank: Regular Contributor
timestamp: March 24, 2018, 11:57:24 am
content: I know there are already a lot of K2000 repair threads but i thought this might be helpful if someone experience similar problems.I won this device on ebay by accident!I wanted to bid for another auction with K2000 and had some serious fingertrouble while switching back and forth with delivery adresses!!!( and i dont consider it a bargain at 200 bucks )Anyway, since i already had it i decided to have a look at it.Before i switched it on i could already tell something is wrong by just turning it in my hands to have a close look art all sides.Some heavy part inside was moving and making ugly metallic sound.After opening it was immediately clear what the problem was ( first two pictures ).Too bad the machine cant tell us what happened. So we can only make wild guesses.Good thing was when switched on it appeared to be working with the exception of the 3rd and 4th digit on the display dead, inclduing the status messages above and below in that column.I disassembled the display board and the damage of the free moving transformer was clearly visible.Half of the pins of the display were bend and "hammered" to the solder-side of the pcb.After lifting them up again with a sharp knife 3rd digit came back to life.( sorry no pics of the "as found" condition )4th digit was a bit more work. I finally found out that some traces on the solderside are important for the display. By using the contact check function of a dmm i could find the damage of a tiny trace.Since i did not know how to repair this in a professional way i just took a small copper wire form the shiled of an old audio cable and soldered it across the damaged trace ( pic 3 ).That revived 4th digit and display was completely working now.Unfortunately the ribbon cable fo the display assembly has three broken wires now ( before only two , but still working) and is dead now.I need to fix that and check the DMM for spec values.At least now its in an acceptable state for the price i paid.And i am bit proud to have managed that "repair".RegardsJoerg
Tek 2465B. - Page 1
Forum section: electronics / repair

author: neo
author_rank: Super Contributor
timestamp: March 23, 2018, 08:30:16 am
content: I'm not one with the digital force, read as, when it comes to programming a chip i'm clueless.To replace the sram in the Tek 2465B will this programmer work?https://www.amazon.com/gp/product/B00K73TSLM/ref=ox_sc_act_title_2?smid=A3H7GPL9U124TQ&psc=1http://www.worldphaco.com/uploads/TEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdfAlso the above document says a FM16W08 WILL work, but i can find no definitive proof. To put that issue to bed once and for all i'm going to buy a FM16W08 and if that don't work a DS1225Y.

author: 0xfede
author_rank: Regular Contributor
timestamp: March 23, 2018, 02:04:47 pm
content: Hi neo,the TL866 supports the DS1225 (RW) as stated here:http://www.autoelectric.cn/minipro/miniprosupportlist.txtbut not the FM16W08.Best,0xfede

author: neo
author_rank: Super Contributor
timestamp: March 23, 2018, 09:37:31 pm
content: Quote from: 0xfede on March 23, 2018, 02:04:47 pmThank you, you just saved me a headache. Wasn't aware china was advanced enough to have a list of supported devices.

author: neo
author_rank: Super Contributor
timestamp: March 23, 2018, 09:51:46 pm
content: I can't find a programmer to support the FM16W08, at least not under 200 bucks, and so i guess batteries it is then. Changing a 20 dollar chip every decade or so is a slightly easier cost to swallow.

author: BravoV
author_rank: Super Contributor
timestamp: March 24, 2018, 02:11:22 am
content: Quote from: neo on March 23, 2018, 09:51:46 pmAs the BBSRAM DS1225Y in this 2465B is already proven to survive and keep running in decades even beyond it's designed life, just buy few spare of them, as it's internal battery is only activated when used for the 1st time.So theoretically these should last probably your life time.

author: neo
author_rank: Super Contributor
timestamp: March 24, 2018, 02:15:33 am
content: Quote from: BravoV on March 24, 2018, 02:11:22 amOnly two small problems with that;How do you guarantee they have not been activated before reaching me?Nominal battery self depletion is equivalent to load

author: BravoV
author_rank: Super Contributor
timestamp: March 24, 2018, 02:19:45 am
content: Quote from: neo on March 24, 2018, 02:15:33 amOf course no one could guarantee that, but assuming you don't buy from eBay as most cheap ones are salvaged or dodgy relabeled stuff.Mine was purchased from Digikey, as last time it was quite fresh from the factory looking at the date code. It was just one or two months back from the purchasing date.Its very unlikely someone at Digikey was tinkering/playing with it before sending it to you.

author: neo
author_rank: Super Contributor
timestamp: March 24, 2018, 03:01:10 am
content: Quote from: BravoV on March 24, 2018, 02:19:45 amThere is always Murphy's law to consider.In all seriousness though once i have the data stored fringe factors are less of a concern.
Hafler DH200 testing - Page 1
Forum section: electronics / repair

author: Birstall
author_rank: Contributor
timestamp: March 21, 2018, 09:35:07 pm
content: I bought this amp in 1981.It has been unused for at least 15 years and when turned on recently, it started smoking. After some research this turned out to be a common issue with the power switch which I have replaced. The amp now turns on normally and all seems to be working but don't trust it.The two power supply capacitors are rated at 16000uF 75v. When powered up they both maintain 62DC Volts. However they dissipate almost immediately when the power is turned off.I have some expensive stereo speakers and don't want to test this amp with those. Knowing nothing about testing amplifier outputs, could someone guide me as to what tests could be used to ensure that they won't blow a speaker at normal output levels.Thanks

author: mzacharias
author_rank: Frequent Contributor
timestamp: March 22, 2018, 09:42:22 pm
content: Not a Hafler expert but I have some experience on them. The bias pots tend to be very flaky and bias will drift or go way out of spec. The spec is that if you remove one of the amp channel B+ fuses, and substitute a milli-ammeter, there should be 250mA when properly adjusted. FYI - for the DH-220 the spec is 275mA and the XL-280, 300mA. If the bias jumps around excessively and is hart to adjust, better replace those pots - they're very hard to clean.
Saleae Logic Pro 8 - Tracking down IC from markings - Page 1
Forum section: electronics / repair

author: tfranco_apexar
author_rank: Contributor
timestamp: March 22, 2018, 01:42:37 pm
content: Hello,I have a Saleae Logic Pro 8 that isn't working. From what I can tell it seems the following IC is damaged, but I haven't been able to ID it.The markings are as follows:QAA (or QRA)LG2* D(the * being the dot for pin1)I found an undamaged one on the board which has clearer markings, photos of both are attached.I'd appreciate any help recognizing the part or telling me where one could search based on the component markings.ThanksEdit: The package seems to match the 0.76mmx0.76mm WLCSP4 and is very reflective, rather than the usual opaque covers.

author: Zucca
author_rank: Unknown
timestamp: March 22, 2018, 03:04:41 pm
content: ehm... contanct Saleae, is the warranty still up?

author: tfranco_apexar
author_rank: Contributor
timestamp: March 22, 2018, 03:07:13 pm
content: I have, I'm waiting on a reply.Not sure on the warranty though, but I'll post whatever the reply was.

author: 0xfede
author_rank: Regular Contributor
timestamp: March 22, 2018, 03:09:12 pm
content: Hi tfranco_apexar,it should be a NCP115ASN180T1G from ON semiconductor.You can find the datasheet here:http://www.onsemi.cn/pub/Collateral/NCP115-D.PDFBest,0xfede

author: tfranco_apexar
author_rank: Contributor
timestamp: March 22, 2018, 03:15:53 pm
content: Thanksbut I don't think that's the one.I have looked through some LDOs, I think it's smaller than a XDFN4 and seems to have different markings than that one.It's kind of hard to measure with a caliper while on the board, so maybe you are right and it's a 1x1 IC.

author: 0xfede
author_rank: Regular Contributor
timestamp: March 22, 2018, 03:20:55 pm
content: Smaller than 1mm x 1mm?The marking is QAA by te way.

author: tfranco_apexar
author_rank: Contributor
timestamp: March 22, 2018, 03:25:59 pm
content: Quote from: 0xfede on March 22, 2018, 03:20:55 pmI think you're right.ThanksOnly thing is that the QAA should be for the TSOP package, not the XDFN4, so it wouldn't match 100%

author: tfranco_apexar
author_rank: Contributor
timestamp: March 22, 2018, 04:56:18 pm
content: Got a reply from their support:"looks like one of our load switches blew. If that is the case, then it's possible other components may have been damaged as well.I'm happy to process a warranty replacement for you."It's been less than 3 years so it should still be in warranty, I'll just have to figure out if the mailing outside the US is a problem.
Help to identify coax RF connector - Page 1
Forum section: electronics / repair

author: Samogon
author_rank: Frequent Contributor
timestamp: February 28, 2018, 05:32:40 am
content: It is used in Agilent power meter connecting power reference socket to to power source on the board.

author: Samogon
author_rank: Frequent Contributor
timestamp: February 28, 2018, 05:48:50 am
content: My best guess is that it is SMC connector. Can someone confirm it?Thank you

author: KrudyZ
author_rank: Frequent Contributor
timestamp: February 28, 2018, 06:22:01 am
content: If it's Agilent then it's most likely SMC.They love SMB and SMC.Measure the OD of the non-threaded section. It should be between 3.63 and 3.71 mm.

author: Berni
author_rank: Super Contributor
timestamp: February 28, 2018, 06:24:35 am
content: Yep looks like SMC to me too. I haven't personally seen them so much in test gear but i did see a lot of SMB in HP gear.

author: AllTheGearNoIdea
author_rank: Unknown
timestamp: February 28, 2018, 12:34:15 pm
content: SMC I think

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: February 28, 2018, 02:14:33 pm
content: https://en.wikipedia.org/wiki/List_of_RF_connector_types

author: flynwill
author_rank: Regular Contributor
timestamp: February 28, 2018, 02:26:32 pm
content: http://www.pasternack.com/pages/Technical-Charts/Connector-Identifier.pdf

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: February 28, 2018, 04:22:59 pm
content: It is an SMC, i had the same problem with the connector in my frequency meter. Do you need one, after I've broke mine I've got some spares to accommodate for future screw-ups.

author: Samogon
author_rank: Frequent Contributor
timestamp: February 28, 2018, 06:38:46 pm
content: Quote from: Ordinaryman1971 on February 28, 2018, 04:22:59 pmI need right angle plug, i am going to fabricate SMC to SMA cable. I have found inexpensive on Chibay but it is crimp type. Now i wonder can i crimp it without special tool which i found nice on digikey for ~$200 for all sorts of coax connectors.So i think buying it for future projects or i can crimp it with pliers and some magic.Can you share what you have done?

author: Samogon
author_rank: Frequent Contributor
timestamp: March 21, 2018, 06:23:59 am
content: Got right angle SMC and used my new crimping tool, worked like a charm.I can now accept crimping requests for any coax connectorsPS It would be impossible to crimp without proper tool, pliers flatten tube and it stays loose. Also tool has properly set force to not destroy connector.So fo $230 i have tool for coax connectors also had to buy rotary stripping tool which cuts nice external isolation the cuts shield then cuts internal isolator and it is additional $30. total 270 with shipment.Keysight sells this cable assembly E4418-61811 for $302 and you have to be a business to able to order parts from them.It is even cheaper to get broken meter for just this part

author: hscade
author_rank: Contributor
timestamp: March 22, 2018, 08:46:25 am
content: Quote from: Samogon on March 21, 2018, 06:23:59 amNeed AIRCELL 7 with MMCX PlugJust kidding
IR3500 Output not working - Page 1
Forum section: electronics / repair

author: Coldwove
author_rank: Newbie
timestamp: March 23, 2018, 05:18:11 pm
content: Hi,I'm trying to get a VRM board to power up outside of it's enclosure so it can be reused for other purposes. The main control chip is an IR3500 and I am having problems getting the chip to fully enable. I have sent an enable signal to the pin, wired the feedback and biased the VRHOT and VRRDY pins as well as set up the VID and VIDSEL, however upon power up all I am getting is 0.18V on the output. Any ideas as to why the chip isn't fully starting up would be greatly appreciated.Cheers.
Studio Light 320 watt-hour unable to achieve full power - Page 1
Forum section: electronics / repair

author: sherwinubaldo
author_rank: Newbie
timestamp: March 22, 2018, 12:55:01 am
content: I have this old Chinese brand Jin Hui Fy-320 that cannot reach full power. Upon checking individual components and replacing some major parts like swapping the capacitors (3pcs 1800uf/350v in parallel) from a working studio light, new BTA12-600R Triac and a new BT152-800R Thyristor.Here is the mystery of the repair adventure; when putting the new BT152-800R it can only reach 120 volts (across the main capacitors for a full minute of recycling) but with the old thyristor it can reach 260 volts in 4 seconds but never the 300 volts expected to give full power. Can someone shed light on the matter? I am attaching images of the board and the thyristor in question. Thanks in advance for the help.Component side:https://drive.google.com/file/d/1oXA1KEtswnAMNjDJwdpBo-28s9TAYkaX/view?usp=sharingConnection side:https://drive.google.com/file/d/1t8muHizl6wWNZ0DFuza-yf8Xkq4LsxZ_/view?usp=sharingOld thyristor on tophttps://drive.google.com/file/d/1TuQ1v07tgFijxyqCSavlXArvM9M9WWUp/view?usp=sharing

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 22, 2018, 02:02:14 am
content: Where did you get the thyrister from? It could be fake or faulty. Just leave the old one in for now.Second, did you do that to the board, or was it already in bad condition? We have soldering advice in the beginner's section as bad soldering can also damage components.It was probably never the triac or thyrister, they usually fail noticably, not with a small voltage drop. Without a schematic, the numbers on the chips would help figure out the circuit.

author: sherwinubaldo
author_rank: Newbie
timestamp: March 22, 2018, 02:14:48 am
content: I got the thyristor from RS Ph component onlinehttps://ph.rs-online.com/web/. They sent me 5 pcs. in a pack. About the soldering job, I had this repaired from where I bought it (3 years ago but it got same problem after just a few months of use) and I was in horror to see the condition of the board upon trying to analyze it myself. I cannot find any schematic diagrams online but my first suspect was the voltage multiplier that is why i had doubts with the thyristor. My friend has the same model and make that is why I was able to swap the capacitors and the voltage readings on his reaches 330 volts in just 6 seconds. Could it be the 6A10 diodes at fault as well?

author: sherwinubaldo
author_rank: Newbie
timestamp: March 22, 2018, 02:23:33 am
content: I will try my best to trace out the schematic and will post it here. The triggering works perfect via sync cord or optical. What value of the resistor should I place between the gate and cathode of the BT152? Oh by the way, i am getting a reading of 80 volts dc on the gate via common wire (black wire going to the negative side of the capacitors) Thanks in advance.

author: sherwinubaldo
author_rank: Newbie
timestamp: March 22, 2018, 02:27:51 am
content: i will look for a resistor then within the 20k ohm range in my bin. Will report back in when I get home to do it.
Fluke 8846A Repair - Page 1
Forum section: electronics / repair

author: mdszy
author_rank: Unknown
timestamp: March 19, 2018, 08:26:46 pm
content: I've recently acquired a broken Fluke 8846A that I'm trying to repair. The failure mode is as follows:The front panel inputs don't work at all. Either they show "overload" or the screen is simply blank. The rear panel works, but only kinda. It has odd behaviors such as showing double the voltage that is actually existing at the input (shows 50V when 25V is being applied, for example) and showing very strange results for the diode measurement, like showing 4V across shorted probes.I've been checking out some other repair threads of similar units, and all the opamps on the unit seem to be in working order, and the LM399 is working fine. However, the LT1394 on the unit (U50) is behaving strangely. In the units current setup, 1V test signal being applied, manual triggering, during idle the IN+ of the chip is at 15mV, IN- is at 0V, Q is at 3.6V and Q' is at 150mV. The chip is being supplied with +/-5V at its +/- voltage inputs. This 150mV as a "low" output seems high to me.Is this chip a potential culprit? Or is it more likely something else?EDIT: Through further testing, I've found out that this chip isn't the problem. Shorting its inputs makes the output change to this "low" 150mV value.I've also tested the Op-amps on the unit and they all seem to be functioning.Thanks!

author: dacman
author_rank: Frequent Contributor
timestamp: March 19, 2018, 11:19:19 pm
content: Try cleaning the Front/Rear switch contacts. It is about the only "repair" I've done to 8845A/8846A DMMs. A quirk with these DMMs is that they will continually flash "Overload" in the default power-on state.

author: mdszy
author_rank: Unknown
timestamp: March 20, 2018, 01:15:22 am
content: Quote from: dacman on March 19, 2018, 11:19:19 pmWell I'll be darned if you aren't a wizard. I don't have any contact cleaner with me, but I just disassembled the switch, cleaned up the contacts a little and lo and behold it works!Thank you so much! I'll still hit it with some cleaner to make sure it stays working, but I'm super happy it was such a simple fix!

author: coromonadalix
author_rank: Super Contributor
timestamp: March 20, 2018, 10:26:40 am
content: lucky you to have found a beast like this, i hope you saved lots of cash.

author: mdszy
author_rank: Unknown
timestamp: March 21, 2018, 12:27:06 am
content: Quote from: coromonadalix on March 20, 2018, 10:26:40 amYep, got it for 78USD shipped, actually! An absolute steal!

author: coromonadalix
author_rank: Super Contributor
timestamp: March 21, 2018, 01:14:32 am
content: arrrgh lucky b@$@% loll 400$ offer loll

author: dacman
author_rank: Frequent Contributor
timestamp: March 22, 2018, 01:14:50 am
content: Is the front panel of the 8846A labeled with 100 mA or is it labeled 400 mA? Fluke used to offer a firmware upgrade that would give the original 8845A/8846A a 400 mA range (and a Ratio function).

author: mdszy
author_rank: Unknown
timestamp: March 22, 2018, 01:16:31 am
content: Quote from: dacman on March 22, 2018, 01:14:50 amIt's labeled 400mA and also has a ratio function!
MP9428a datasheet or pinout? - Page 1
Forum section: electronics / repair

author: manu
author_rank: Regular Contributor
timestamp: March 21, 2018, 10:58:30 pm
content: Hi,I have a Sony bluetoth speaker srs-xb20 with a charging issue.I suspect the Monolitic Power System chip MP9428a but I cannot find a datasheet nor a pinout.The only source is their online dc/dc tool, so if you know this chip, I would be glad to have more infos.Thanks!

author: Chriss
author_rank: Frequent Contributor
timestamp: March 22, 2018, 12:30:52 am
content: Hi!Try this picture from the attachment.I know, it's not the same ic but try to identify the circuit and maybe this ic is the same pinout as yours.Just give a try.Let as know if this is or not good.My best regards.Sent from my GT-I8260 using Tapatalk

author: Chriss
author_rank: Frequent Contributor
timestamp: March 22, 2018, 12:32:33 am
content: In case the attachment not visible, because I post through Tapatalk and from my phone...Sent from my GT-I8260 using Tapatalk

author: manu
author_rank: Regular Contributor
timestamp: March 22, 2018, 12:37:23 am
content: That seems to be very close to what I have, thanks!

author: Chriss
author_rank: Frequent Contributor
timestamp: March 22, 2018, 12:48:54 am
content: You are well come!Sent from my GT-I8260 using Tapatalk
Fluke 289 - Lead detection? - Page 1
Forum section: electronics / repair

author: orion242
author_rank: Unknown
timestamp: March 21, 2018, 11:20:49 pm
content: Does anyone know how the 289 does the lead detection? Mine is having fits at times popping up the error that the leads are inserted wrong. When this happens, it doesn't matter which way the leads are inserted, current or voltage. You can spin the dial thru all modes and it just beeps away and is completely useless. If I plug them in and out, wiggle things or just bang it on the bench it finally stops. Last time I was in it, I thought it looked like it was optically sensing this? Is that correct? Maybe its just dirt in the sensitive bits, bad ir led or detector?The metal contacts on the battery compartment are rather beat up, so I hate opening it more than I have to. Just looking for some direction to get in and out in a single shot.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 22, 2018, 12:15:45 am
content: Quote from: orion242 on March 21, 2018, 11:20:49 pmSeehttps://www.eevblog.com/forum/repair/fluke-189-teardown-repair/http://mrmodemhead.com/blog/gallery/fluke-189-clean-up/https://www.eevblog.com/forum/beginners/my-fluke-289-displays-'warning-leads-connected-incorrectly'-after-the-case-open/

author: orion242
author_rank: Unknown
timestamp: March 22, 2018, 12:38:19 am
content: Perfect. Thank you and the OPs in the other threads!DS2 just as in the third link had broke lose. Found it floating in the case, repaired and its back in action.
HAMEG HM8030-3/ HAMEG HM8011-3 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 17, 2018, 03:29:10 pm
content: Hello everyone! I search schemas for HAMEG HM8030-3 and HAMEG 8011-3. Can someone help me? Thanks in advance!

author: abraxa
author_rank: Frequent Contributor
timestamp: March 17, 2018, 04:56:00 pm
content: Does this help you?https://www.radiomuseum.org/r/hameg_digital_multimeter_hm8011_2.html(not sure why the URL says -2 when it's about the -3 model)Also, the 8030-4 page athttps://www.radiomuseum.org/r/hameg_funktionsgenerator_hm_803.htmlmay help. There's also a page there about the 8030-2 but unfortunately none about the 8030-3 in particular.

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 17, 2018, 05:24:25 pm
content: Thanks for your help, but I have already been to this site, and I do not understand how to get the different schemas. How to do?

author: abraxa
author_rank: Frequent Contributor
timestamp: March 17, 2018, 06:22:05 pm
content: Just click on the schematics on the right, enter your name/email and you'll have it.

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 21, 2018, 07:02:36 am
content: Hello; I had schemas thanks to a request made at HAMEG ......

author: Assafl
author_rank: Frequent Contributor
timestamp: March 21, 2018, 10:18:18 pm
content: Can you post them here?Thanks,Assaf
Tektronix 2221 Restoration Help! - Page 1
Forum section: electronics / repair

author: XMA
author_rank: Contributor
timestamp: March 21, 2018, 08:10:26 pm
content: okay guys so yesterday i had bought a Tektronix 2221 for $120 and it works and no problems, but its dirty and like how i usually go after dirt on some stuff i take my rubbing alcohol and rub it off, and so i did to the blue metal casing and the damn paint starts rudding onto my cloth, wtf. so what can i use to clean it without damaging its paint?Also with that theres these rubber things on the front and back, they seem to be glued onto the metal housing, how would i go on removing them and should i even do so.
Floor fan motor getting extremely hot (>70°C) - Page 1
Forum section: electronics / repair

author: attr_writer
author_rank: Newbie
timestamp: March 21, 2018, 11:49:14 am
content: Hi allFirst-time poster here but have been watching Dave's videos for years.I recently took apart a floor fan to service the bushings (no bearings here) and noticed that the motor gets incredibly hot (measured over 70°C), even when set to slowest and no fan blades attached.Is this normal for a motor of this type or should I bin it? I have attached a photo for reference.Any suggestions appreciated.

author: Andy Watson
author_rank: Super Contributor
timestamp: March 21, 2018, 12:42:22 pm
content: Probably.Quote from: attr_writer on March 21, 2018, 11:49:14 amIt is probably designed to experience the cooling effect of its own fan - which you have removed.

author: attr_writer
author_rank: Newbie
timestamp: March 21, 2018, 01:03:14 pm
content: Quote from: Andy Watson on March 21, 2018, 12:42:22 pmThanks for the reply. Even with the blades attached, it still gets very hot. Guess it's time to e-waste it.

author: Fraser
author_rank: Super Contributor
timestamp: March 21, 2018, 01:06:44 pm
content: Be aware that many fan units use the air flow created by the fan to cool the motor. With no fan attached, the motor can heat up.70C is not that bad for a mains motor. Overheating in a simple fan motor is usually caused by tight bearings/sleeves due to dried out or contaminated oil/grease. A more serious failure is a short in the windings due to insulation failure.I rebuilt a fan motor recently as the Oilite sleeve bearings had dried out. The sleeve was actually packed with dried oil and dust. I soaked the oilite sleeve bearings in acetone. I have an ultrasonic bath so placed the jar containing the bearings and acetone in its water bath. A few minutes in there brought out all the old oil and muck ! I refilled the oilite bearings by placing them in a jar of hot motor oil and then drew a vacuum on the jar using a car brake system vacuum bleed unit. The bearings sat in that vacuum overnight and I could see the air coming out of the phosphor bronzeThose oilite bearings are now running very well as I caught them before they got worn due to lack of lubrication. Note that I had previously tried removal and surface lubrication on the bearings. The bearings quickly became tight again due to the dried contamination on their surface.Fraser

author: Seekonk
author_rank: Super Contributor
timestamp: March 21, 2018, 02:35:45 pm
content: Sub HP motors are just very inefficient. I don't think replacing it would change anything.

author: oldway
author_rank: Super Contributor
timestamp: March 21, 2018, 03:16:08 pm
content: How did you measure the temperature?What was the ambient temperature?
Fijifilm AX560 won't turn on without batteries, even with SMPS - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 07, 2018, 01:25:59 pm
content: I've soldered on wires to the battery terminals of the camera, so I can power it off a SMPS. Apparently this thing won't run off its USB port, (I should check the manual). I got zapped by the 300V caps in the process, took them down to 220V through my finger. That was left from the batteries, I had no idea, and the solder joint for it is just sticking right out !!!But now the only way for it to work, is with the batteries in the case and its door closed. I don't see any switch. And I don't see the memory card getting pushed down any like on some cameras.Without the batteries, and me inputting 3V it tries to start, but shuts right off. With the AAs in place and the 3Vin it works, so it's not some over-current protection.The battery door connects the 2AA in series. I was wondering if something was checking if 1/2 the voltage was there

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 25, 2018, 06:50:54 pm
content: I put 1.5V on the battery door from 10k/10k , and still won't turn on without batteries in the case, why ? The door is hard too close with the batts in, I don't see any switch or button/etc that should care if batts are in/outmaybe it needs a much higher current from the 1.5V ?

author: sleemanj
author_rank: Super Contributor
timestamp: March 25, 2018, 11:28:29 pm
content: My guess would be a current issue, namely that your supply can't supply the current required, AA cells can1. supply a pretty decent amount of current2. are right there in the battery compartment unlike your DC supply which is only some long wires a long way from the compartmentPut a decent sized cap across the battery contacts and see if that helps.
Old Telefunken preamp plz help!! - Page 1
Forum section: electronics / repair

author: DThodoris
author_rank: Newbie
timestamp: March 21, 2018, 12:00:50 am
content: Hello everyone, i have a very old piece of equipment its a Telefunken preamp made in Brasil.Unfortunately i dont have any other information...It doesnt have tubes on (i dont even know what type of tubes to put) and it is said to be faulty.Any help regarding schematics would be appreciated! (google did not help on that i couldnt even find a photo of the preamp!)

author: DThodoris
author_rank: Newbie
timestamp: March 21, 2018, 12:02:49 am
content: And a gutshot

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 21, 2018, 02:57:01 am
content: Be careful! Brazil is mutli-voltage, make sure it's set to 230V (If that is a voltage selector)There's no tube chart on the bottom or inside or anywhere? Sometimes the numbers are stamped next to the sockets too. If not, try to find a model number on the chassis.EDIT: That's really weird...why so many connectors? And what's that yellow cable?
Replacing a Rigol MSO1074Z fan with a silent fan, almost useless tutorial !!! - Page 1
Forum section: electronics / repair

author: DC1MC
author_rank: Super Contributor
timestamp: March 20, 2018, 10:47:05 pm
content: Hi, today I've replaced the nosy fan of my Rigol scope with a silent one, please thumbs up to my Youtube channel, read my 6 page blog post and support me on my Parteon channel for future tutorialsAre you guys kidding me, I would have chocked on my vomit to do yet another lame video, so you have to live with this lame postSo here's the deal, the fan is from here:https://www.ebay.de/itm/SCYTHE-Mini-Kaze-50mm-Gehäuselüfter-z-B-HTPCs-Northbridge-externe-Festplatten/361944246434Open carefully your scope with a T10 screwdriver and replace it by carefully following this short advices:Put the screws in a small box, you will lose them, two screws are under the handle.If you have the signal generator option, make sure to use a duck-beak plier or a tubular key to unscrew the nuts holding the BNC sockets. careful to not scratch them and don't overdoit when you put them back.Remove all conveniently red marked screws after you've removed the back lid.CAREFULLY, lift the power assembly half, carefully I've said, or you already ripped the fan connector, told you so, if you didn't ripped it yet, then carefully remove the red-black wire with a white connector.Unscrew the for auto-screwing screws and put them in the little box.Remove the new fan from the package and using a needle push the tabs and SWITCH the red black wires (see picture V2, V2 comes from Ventilator 2 not the German rocket).BEFORE putting the new fan in place, screw the auto-screwing screws PERPENDICULARLY, not crooked hillary in the fan, make sure that you don't use these new fangled electric screwdrivers or you will screw the screw hole.After you remove the screwed screws put the new fan in the case with the wire egress point facing the back wall, such that the wire toüches the PS shielding, use the anemic wire guide there and twist the cable like the original one for 0.003dB/uV decrease of noise.Connect the socket (you didn't forget to reverse the wires, or your scope, fan and PS will BURN!!!)Carefully screw als the screws back.Start the scope and be amazed on how quiet it is, eventually look how nice it burns if you forget to reverse the wires in thr socket.Pack the old fan in the new fan package and try to sell it.Observe the attached pictures.Than you for your attention, I disclaim all the warranty and suitability of this tutorial for the intended purposes, if you'll manage to damage your scope changing a bloody fan, that you're done with any electronics work, sell everything and start collecting stamps.FOR SALE: ORGINAL RIGOL FAN IN BOX, REMOVED FROM A WORKING UNIT, ALMOST NEW, NO MORE THAN 4 YEARS, IT VENTILATES LIKE CRAZY, SEE THE LAST PICTURE, ALL OFFERS CONSIDERED!!!SPECIAL BONUS: ADAPTER 2 PIN TO 3 PIN!!! SEE PICTURE V3 !!!
LG monitor repair advice - Page 1
Forum section: electronics / repair

author: mathsquid
author_rank: Frequent Contributor
timestamp: March 25, 2018, 03:49:17 pm
content: I'm trying to repair a monitor that has some bad capacitors in it, but I wanted to get some advice before I proceed. There's some discoloration on the power supply circuit board, and there's some weird cracking in the solder behind two diodes.The monitor won't switch on, but when I plug in the power supply board (while disconnected from the rest of the monitor), I get correct voltages on the header. I'm guessing this may be because there's no load, and that it can't provide enough current when under load.I'm probably going to replace the three bad capacitor and just see if that fixes things, but any advice--especially about the cracked solder behind the diodes would be appreciated.

author: wraper
author_rank: Unknown
timestamp: March 25, 2018, 03:54:45 pm
content: Quote from: mathsquid on March 25, 2018, 03:49:17 pmThat's not a cracked solder. Look how those look on the component side, those are metal inserts which add mechanical strength to the solder joints.

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2018, 04:29:47 pm
content: I would replace all 6 Sucons ( appropriate name, SUSpect CONdenser) with new ones, and also replace the 2 small electrolytics on the primary side by the switching controller, they will be near to failure from being toasted by the hot parts near them, and will fail soon if not replaced. Resolder the 2 power diodes as well, they are rather well known to crack the solder joints by the rivets, so resoldering all those joints is a good idea, along with the joins on the power transformer and the mains connections as well.

author: rfengg
author_rank: Regular Contributor
timestamp: March 26, 2018, 02:22:57 am
content: From your 1st pic , three electrolytics caps clearly show bulged tops.........surely the ESR and / or cap value must be out of spec on these........its best to change to all electrolytics just to be sure.

author: Crazy_Engineer
author_rank: Contributor
timestamp: March 26, 2018, 04:17:11 pm
content: Quote from: SeanB on March 25, 2018, 04:29:47 pmFollow this advice. You don't want to have to open it up in a few months to replace the old capacitors you did not swap out.
Thermal paint/paste for transistor - Page 1
Forum section: electronics / repair

author: Birstall
author_rank: Contributor
timestamp: March 19, 2018, 07:35:26 pm
content: I have a Hafler DH200 amplifier (bought in 1981).I have replaced the toggle switch but in the process, one of the round metal transistors fell off one of the output PCB's. From the circuit diagram i believe it is a 2N5415.Around the body of the transistor is a 'winged' heat sink which is attached with a dark red 'paint' or paste. I have been unable to discover what this 'paint' is although I assume it's some kind of thermal mediumI'd be obliged for some guidance as what i can use to reattach the heat sink.This photo is not mine but highlights the part I'm talking about.Thank you.

author: Gyro
author_rank: Super Contributor
timestamp: March 19, 2018, 08:22:47 pm
content: I suspect that itisjust paint - the sort they use for locking preset pots etc. to stop it coming loose. The thermal resistance of the little tab heatsink is so high that thermal compound wouldn't make any difference against the sprung metal to metal contact.

author: Rog520
author_rank: Regular Contributor
timestamp: March 19, 2018, 09:03:03 pm
content: Thermal epoxy is sometimes used, but the heatsink wouldn't have fallen off if it was epoxied. Probably just a very basic glue...or paint.
Saving a custom RJ12 connector - Page 1
Forum section: electronics / repair

author: McBryce
author_rank: Super Contributor
timestamp: March 21, 2018, 02:06:02 pm
content: Hi,I'm trying to repair a device that has a custom shaped RJ12 type connector (6 pin). The cable is badly damaged and needs to be replaced. I could use a new standard RJ12 connector, but it would be nice if I could re-use the original as it blends into the housing of the device at a position that's quite visible and also provides some dust/dirt protection. Does anyone know any neat tricks to extract the pins of an RJ12 connector without damaging the connector? I've poked around with pins, tried the strongest neodynium magnet I own and tried knocking / vibrating the connector, but there's no budging them.Please leave your wildest, craziest suggestions below.McBryce.

author: drussell
author_rank: Super Contributor
timestamp: March 21, 2018, 02:59:36 pm
content: When I was a kid, I used to re-use RJxx connectors by prying the pins out using something like a small finishing nail or a large safety-pin. Once you get them moving by prying up at the ends, they will come out. Pry each one from one side to the other and wiggle.If you damage any of them, steal new ones from another jack. As long as you don't mangle the actual plastic carrier too badly it will work just fine.

author: McBryce
author_rank: Super Contributor
timestamp: March 21, 2018, 03:29:22 pm
content: Prying with a needle didn't work, they just tilt and get jammed. Unfortunately, due to the connectors plastic there's only access to one side.McBryce.

author: SeanB
author_rank: Super Contributor
timestamp: March 21, 2018, 07:41:14 pm
content: Bend the needle into a fishook shape or use a fish hook with the barbs on the shank ground off to get to the other side. Rob a new connector for the pins if they are the right size and reterminate the cable.

author: McBryce
author_rank: Super Contributor
timestamp: March 22, 2018, 07:56:04 am
content: I'll give it another go.McBryce.
12-240v 1kw inverter repair. - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: March 18, 2018, 08:47:02 pm
content: hi all ive a 1kw in verter to repair its got o fet gone sc,thats blown up a couple of driver transistors as well,the problem i have is the gate of the fet is driven via a 16th watt resistor thats been cooked,it measures 10 ohm,would that seem about ok as i cant read the markings any more,cheers m3vuv.

author: james_s
author_rank: Super Contributor
timestamp: March 18, 2018, 09:34:26 pm
content: 10 Ohm sounds pretty reasonable, I've seen anything from about 2.2 to 10 Ohm typically used. The actual value is not normally all that critical, although it wouldn't hurt to scope the gate pin and look for any ringing.
Takeda Riken 4132 Spectrum Analyzer - Page 1
Forum section: electronics / repair

author: FB72
author_rank: Contributor
timestamp: March 17, 2018, 01:52:16 am
content: Hello All,Iv'e been stalking and reading many of the good topics here and I finally found a reason to post! I recently acquired a TR4132 Spectrum analyzer with the optional memory unit for my hobby lab. The analyzer is in very good cosmetic shape and works quite well, once warmed up. The attenuator is not damaged and the calibrate signal displays at the correct level in all settings, so I was relieved to find that! What really helped me make my decision to get this unit is that Advantest has the entire operator/calibration/repair/schematic manual online. (for both the analyzer and memory unit)Anyway, the one issue I have is the momentary pushbuttons on the memory unit are shot. They have a rubber contactor in them that has dried and become brittle. So all of the buttons need replaced, which could be interesting if I want to fit something that won't look horrible in the front panel. I haven't done much searching for replacements yet, but I was wondering if anybody may have come across something similar or have an idea where to search? (Pics of button at end, and I'll get some measurements if anyone is interested)Thanks!, check out the following pictures for some eye candy inside the machine.Here is a picture of the analyzer showing the cal signal at 100Mhz/divisionAnother view of the cal signal, at 100Mhz (notice the center frequency isn't at 100Mhz, it took awhile to warm up but once up to temp, it quit drifting and settled at 100Mhz)TopsideBottom sideMemory board, look at all the 74LS logic!!Finally the buttons that are the issue:Button disassembled, can see the rubber contact that has dried and fell apart:

author: FB72
author_rank: Contributor
timestamp: March 18, 2018, 01:20:25 pm
content: I wasn't able to find any buttons that would neatly fit in the current panel, but I was able to fit a cheap tactile pushbutton under the housing of the current buttons. They work O.K. but would be better with something that fit better. But I don't see myself using the memory function much anyway, but its working again!Not the prettiest fix, top one that has the glue around it has a push-button under the shell.Here is the memory in action, has a saved "screen-shot" overlayed with the current signal.
54622D Battery Replacement Question - Page 1
Forum section: electronics / repair

author: tip29
author_rank: Newbie
timestamp: March 16, 2018, 07:13:52 pm
content: Hello all,I just bought a used HP 54622D oscilloscope. When I boot up it comes up with battery warning/error.Does anyone know if it needs to be factory calibrated after replacing the battery?Anyone?Thanks.

author: wn1fju
author_rank: Frequent Contributor
timestamp: March 17, 2018, 03:22:09 pm
content: It shouldn't. However, there is a user calibration process that you probably should do in any event. Just bring it up from the menu andfollow the instructions. If you don't already have the service manual, just google it and get a free download.

author: tip29
author_rank: Newbie
timestamp: March 18, 2018, 10:29:58 pm
content: Great. Thanks.
Marantz 1072 speaker output voltage spike when switching on - Page 1
Forum section: electronics / repair

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: March 15, 2018, 11:26:34 am
content: Dear all,I fixed an old Marantz 1072 hifi amplifier that was not working and blowing fuses.I could work out almost all of the clunky bits someone put in it in an effort to "fix" it. That dude somehow thought it was a good idea to connect the -39V and +39V rails together with a thick jumper cableThe amp is now working, I get amplified audio on both channels and everything is fine, except when starting up the amp.There is a nasty voltage spike and DC offset on the speaker outputs when switching on the amp. It settles after a couple of seconds, so switching of the outputs, power cycling the amp and then switching on the outputs after some time does not get the speakers killedHowever, I want to get rid of that issue.Attached is part of the schematic and a scope capture of what I get on the speaker output.Edit: Nothing connected to the input of course!Also, here is a link toa scan of the service manual.If one of the power caps (C808, C809) was leaking, could this result in the observed behavior or should I be looking some place else?Thanks and kind regards,Frederik

author: oldway
author_rank: Super Contributor
timestamp: March 15, 2018, 01:44:05 pm
content: Generally most dc-coupled amplifiers have a relay that protects the speakers against a dc component that could damage themThe relay will only switch on if both amplifiers have an output voltage of less than 500 mV.It's strange that this amplifier does not have such a relay.During power on and power off, imbalance and asymmetry may occur if the capacitors have lost their capacitance.This causes the presence of a DC component that prevents or delays the switch on of the protection relay.But here there is no relay .... !!!!!!I advise you to replace all the electrolytic capacitors of power supplies (main power supply and auxiliary power supply) as well as all the electrolytic capacitors of the power amplifiers.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: March 15, 2018, 02:04:46 pm
content: Of course it was the power caps. It’s always the power caps xDHere is the transient I get after replacing the old Nichicons with new Rubycon 6800uF, 63V. That, I can live with.Bzw. No, this amp does not have relays.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 17, 2018, 01:32:41 pm
content: yeah its a good spike, i would check all psu caps, as oldway says : the supply rails when starting are'nt equal and the amp will output dc component, personally i would add a time delayed relay in the speaker outputs.If everything in the amp is okay, the biais adjustments are okay etc ... i would change all electrolytics in your amp section c704 708 720 722 etc... and the other channel too, wont cost a fortune.In the past i had an biais transistor who was going nuts after a while, the amp started fine but after an hour, dc component began to appear