hybridfree/eevblog-posts huggingface dataset:
Icom IC-R9000 power unit - Page 1
Forum section: electronics / repair

author: Khitry Lis
author_rank: Newbie
timestamp: July 09, 2018, 11:58:30 am
content: Good day everyoneThis weekend I bought a broken Icom IC-R9000 receiver. quickly I located the problem to be in the power unit.The capacitors C5 and C6 were totally dried out and therefore I replaced those.After replacing those I had still no success in getting the receiver to work again. Therefore I continued measuring for broken components. I found out that after Q2 I measure 0 Volt so I suppose that Q2 is broken also.Does anyone know how I can be sure if Q2 is broken or could the problem be in Q1 (the base voltage of Q2 seems to be rather low to me) or with any of the zener diodes?And if Q2 is broken with what kind of transistor can I replace this 2SD797 transistor? I've been searching online for this transistor and it looks to me that this transistor is out of production. To which values do you have to look to find a equivalent?

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 09, 2018, 12:10:23 pm
content: You have 2 arrows pointing to the same wire, one with 17V and one with 21V ??What do you measure on Q2 if you pull P5 from the back?

author: Khitry Lis
author_rank: Newbie
timestamp: July 10, 2018, 08:59:53 am
content: I have made a mistake in drawing the arrow, the 17v arrow is wrong but I am not sure now anymore where I measured the 17v.Unfortunately I'm not able to look at the receiver again before this Friday. By this time I will write here again with my new findings.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 10, 2018, 09:46:14 am
content: I would try an 2n3055, they are easily found, you have 2N3772, 2N5686, 2N6338, 2N6339, 2N6340, 2N6341 ... any TO-3 case NPN who has 20 amps collector current.You have an 4 amp fuse in the line, it would help start the radio.Do you have an beefy 13.8v 20 amps power supply around, fixed or variable current limited just in caseyou could try to put an supply on p4 pin 1 (DCI) once p5 is removed.Q2 is not necessarily broken, it is an powerful transistor, 100v at 30 amps, normally they wont go up easily, unless a thermal breakdown, badly dissipated heat ... killed it.You have Q1 and Q3 to check, all the zenners, electrolytics ... low values ceramic or mica capacitors.The 2 zenners in serial give 10.2 volts (5.1v each)All this circuit to make an 13.8v regulator ... no current limitation.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 10, 2018, 09:52:28 am
content: A battery would be a very bad idea if there is a short in the radio, unless you want to smoke the pcb traces. That is why I asked to remove P5 and measure again to find out if the problem is in the power supply or in the radio.
LeCroy rotary encoder axle/shaft - Page 1
Forum section: electronics / repair

author: spilihps
author_rank: Regular Contributor
timestamp: July 09, 2018, 05:27:24 pm
content: Hello!Iam currently repairing a LeCroy 454, and it is missing a couple of rotary encoder axle/shafts(whatever it is called?)The encoder itself is working fine.Are these shafts avaiable somewere?The knobs themselfs seems to be still available from lecroy.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 09, 2018, 11:19:26 pm
content: On the LeCroy 94xx scopes, the shaft is part of the rotary encoder (made by Bournes) and neither part is available from leCroy. I haven't found the exact Bournes part anywhere but a similar model should work or you can probably take a new encoder apart and get the shaft. Or just get the right encoder from salvage. For knobs, I use knobs from some of the OLD Tektronix scopes. They're red but who cares.
Bricked My Rigol DS2072A-S -- FIXED! - Page 1
Forum section: electronics / repair

author: Melt-O-Tronic
author_rank: Frequent Contributor
timestamp: July 08, 2018, 02:18:35 pm
content: Well I've finally done it. I tried to do a firmware upgrade last night to fix a bug (going from v00.03.03.01.00 to v00.03.05.03.03). The progress bar stopped moving at around 10% within a minute or two and didn't move for the next 2 hours. I managed to convince myself that it was probably just decompressing and hadn't gotten to the point of no return, so I eventually power cycled it. Stupid move.Now, the splash screen comes up and it goes into a perpetual reboot cycle about every 3 seconds. I have a memory dump file I did via SCPI command about 3 years ago in preparation for Riglol. Is there any chance I can shove that back in with a hardware programmer? Or am I going to have to bite the bullet and beg Rigol for help?

author: Samogon
author_rank: Frequent Contributor
timestamp: July 08, 2018, 04:55:49 pm
content: So power button + help button trick is not working to go to FW update mode?

author: Melt-O-Tronic
author_rank: Frequent Contributor
timestamp: July 08, 2018, 09:44:28 pm
content: OMG, Samogon. I've read soooo many DS2072 posts and totally missed that. I did it and my scope is back AND the firmware update is successful.THANK YOU!!!https://www.eevblog.com/forum/testgear/unlockinghacking-the-rigol-ds2000a-series-scope-the-short-post/
Tektronix Type 547 channel B not triggering - Page 1
Forum section: electronics / repair

author: The Guy
author_rank: Regular Contributor
timestamp: October 05, 2017, 04:40:29 am
content: Hi all...I decided to continue tackling the repair of my beautiful tek 547 oscilloscope. It is working quite well... but it still has a few problems.The main issue right now is that channel B trigger circuit seems to be not working at all, no matter what the settings or the circuit pots adjustment are the trace seems unaffected.I´ve been reading and some fellas that had the same problem ended up discovering that the faulty component was one of those tunnel diodes, but i checked them out and compared the readings with the ones from channel A and they read the same.I am a complete noob regarding triggering circuits... so not sure where or how to start. Any suggestions?Thanks a bunch.

author: rajeshvs
author_rank: Newbie
timestamp: July 08, 2018, 01:19:12 am
content: way too late reply still if it helps, check this -https://lazyelectrons.wordpress.com/2018/07/06/tektronix-547-oscilloscope-restoration/Could be the tunnel

author: KE5FX
author_rank: Super Contributor
timestamp: July 08, 2018, 06:34:22 am
content: Some very nice work on the 547, definitely.Have you found that a lot of the carbon-comp resistors have drifted upward in value? I'm curious as to when that phenomenon started.... it seems that the oldest resistors fare better over time than the newer ones from the 1970s-1980s in many cases.

author: rajeshvs
author_rank: Newbie
timestamp: July 08, 2018, 03:21:43 pm
content: I did not find a resistor drifted too much in a Tektronix. All the 3 Teks I have worked never had a resistor with bad tolerance, or they were not bad enough to catch my attention or create trouble to me. But they all were from 60s, before the window you mentioned, So guess your assumption is correct.I did a 549 Analog Storage -https://lazyelectrons.wordpress.com/2018/01/11/tektronix-549-restoration/and a RM35A(535A) too -https://lazyelectrons.wordpress.com/2018/03/14/tektronix-rm35-rescue/
Help me identify this diode - Page 1
Forum section: electronics / repair

author: cjapilu
author_rank: Newbie
timestamp: July 15, 2018, 08:08:42 am
content: Hi to everybody, first time in this blog, need some help to identify a diode from vishay company, the circuit is mounted on a truck and controls the pto (power take-off) basically drives the motor (12v) to engage the shaft (switch it on and off) the board originally was made for a crane so it has even controls for lift up and down but that side is not used. the diode (but there are multiple ones labelled the same) it's an smd type (CM 0CA) i suppose it could be a zener but could be also an esd, body is 3x4mm feets 2mm large (maybe 1W?), a new board will cost me about 350€ and (of couse) the manufacturer wont give me the specs. I would appreciate any idea, thanks

author: cjapilu
author_rank: Newbie
timestamp: July 15, 2018, 08:11:51 am
content: that's a picture of the board angle ( the other one is on the other side will post soon another image) whit two of those

author: isometrik
author_rank: Regular Contributor
timestamp: July 15, 2018, 09:02:51 am
content: Possibly aSMBJ33Abi-directional 33 volts (stand-off voltage) TRANSZORB®.It would fit the device marking code found on page 2 of the following datasheet:http://www.vishay.com/docs/88392/smbj.pdf

author: isometrik
author_rank: Regular Contributor
timestamp: July 15, 2018, 09:10:55 am
content: I forgot to mention that I used the VishayDiodes Group Body Markingdocument (http://www.vishay.com/docs/88912/diodesgroupbodymarking.pdf) to figure out what the marking corresponded to.Assuming that the component you refer to has aSMB (DO-214AA)body, "CM" would correspond to the diode type, while "0CA" would correspond to the date code. Refer to page 4 of the document for more details.
Need help replacing TRRS on headset - Page 1
Forum section: electronics / repair

author: Rocholl
author_rank: Newbie
timestamp: July 05, 2018, 02:16:18 pm
content: Repairing corsair void headset as my cat chewed the wire to bits. I've shortened the wire and want to put a trrs plug so I can use a braided extension cable to avoid the problem happening again,Left and right ear work fine when soldered but cant get the microphone to take any input, all I get is static, I'm a little confused by the wiring as the microphone wire seems to be a copper wire in white insulation covered in more copper wire, I've tried soldering both, only soldering the core all with no success.Please can anyone that has experience replacing trrs point me in the right direction as I'm completely lost now, buying a terminal to see if its just bad soldering but I cant get the microphone to work even by holding the wires onto the connection (ground and microphone). The microphone itself was working the day before and it wasn't dropped at any point so I doubt the fault is there.The only possibility I've come up with is the first time I went to wire I was extremely tired and actually wired everything in reverse, not sure if putting an audio signal into the mic could have completely bust it, I doubt it but I figured it was worth mentioning

author: Rocholl
author_rank: Newbie
timestamp: July 05, 2018, 02:32:49 pm
content: after resoldering I now have nothing on the microphone line unless I play audio and record at the same time in which case i get the audio on the recording, however i cant see any shorts, picture for reference.

author: mathsquid
author_rank: Frequent Contributor
timestamp: July 05, 2018, 02:54:24 pm
content: Quote from: Rocholl on July 05, 2018, 02:32:49 pmHave you tested it for shorts using a continuity tester? It sounds to me like one of the audio lines is shorted to the mic.

author: Rocholl
author_rank: Newbie
timestamp: July 05, 2018, 03:02:36 pm
content: haven't got a multimeter unfortunately, but I agree thats what I assumed so I resoldered it to a new plug entirely and still have the same issue

author: Rocholl
author_rank: Newbie
timestamp: July 06, 2018, 10:28:51 am
content: So I've now replaced with a solderless terminal and I am still having the same issue where the mic doesnt read my input and only reads a small version of my audio output e.g. music im playing in earphones when recording. Anyone have any idea what the issue could be here, have I well and truly fucked the headphones themselves by wiring it up wrong at some point?

author: tooki
author_rank: Super Contributor
timestamp: July 07, 2018, 01:56:39 pm
content: If the mike is the white wire with braid, then that’s the mike and its ground. You have *five* wires that have to go to *four* terminals, but it looks like you’ve only wired four wires.Try this:Tip: left (green)Ring: right (red)Ring: grounds (both the mike braid and the green/white ground for the channels)Sleeve: mike (core)
(UK) source of flat belts for pick and place system - Page 1
Forum section: electronics / repair

author: philpem
author_rank: Frequent Contributor
timestamp: July 04, 2018, 06:21:16 am
content: I'm working on repairing my MDC ECM97 pick and place system, and now the time has finally come to replace the worn out PCB loader conveyor belt.Does anyone know of a reliable UK source of ~2mm thick "seamless" flat belts, 6mm wide and 1830mm in circumference/length?The majority of the ones I've found start at 10mm.ThanksPhil(A previous version of this message listed the belt size as 1940mm. It's actually 1830mm. Needless to say a 1940mm belt is rather too long for the machine, unless you want to fit an idler pulley to the belt)

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 04, 2018, 08:01:52 am
content: If you can find a wider one, it probably wouldn't be hard to make a simple jig to trim it down

author: philpem
author_rank: Frequent Contributor
timestamp: July 07, 2018, 06:31:06 am
content: Yeah, that was my backup plan.I've found a 10mm wide belt at a local bearings supplier, just waiting for it to arrive. I can probably make up a fairly precise belt cutting jig on the lathe if I need to.

author: philpem
author_rank: Frequent Contributor
timestamp: July 07, 2018, 10:15:46 am
content: Joy, turns out I mismeasured the belt. It's actually 1830mm... which leaves me with a pair of 1940s to experiment with the belt cutting rig.
HP8590L spectrum analyser  CAL: SPAN SENS FAIL - Page 1
Forum section: electronics / repair

author: Bjoern
author_rank: Contributor
timestamp: July 09, 2018, 01:20:43 pm
content: I bought my spectrum analyzer second hand recently and had to replace two tantalum capacitorsbefore I was able to start it up.When I now try to run the self cal mode i run into the CAL: SPAN SENS FAIL error.What is the likely cause for this problem ?Could I get an electric schematic somewhere ?When I connect a sine wave signal generator I do not seem to get a sensible signal.Since I have never used a spectrum analyzer that was working I am not familiar with its settings which doesn't help in troubleshoot either.I suspect that the error is caused due to age as the damaged capacitors in the +15volt line suggests.Whats the advice ??
Schematic for Tenma 72-705 - Page 1
Forum section: electronics / repair

author: JS_NY1
author_rank: Newbie
timestamp: July 04, 2018, 01:19:29 am
content: I recently unearthed a Tenma 72-705 dual laboratory power supply. One channel works beautifully, the other channel outputs the maximum voltage with no control. I have a very poor quality schematic for this unit. Does anyone have a good, clean schematic they could send me? Thanks, Jim KC2ZVK

author: Chris56000
author_rank: Frequent Contributor
timestamp: July 04, 2018, 06:28:52 pm
content: Hi!Would you mind posting the poor–quality diagram you do have please?I might be able to redraw it for you if it really isn't too indecipherable!Chris Williams

author: bitseeker
author_rank: Super Contributor
timestamp: July 06, 2018, 02:22:14 am
content: Hi JS_NY1,Welcome to the forum. If that's a linear power supply (I didn't see much with that model number), it sounds like the power transistor on that stuck channel is shorted. Remove it from the circuit and check. If it is shorted, then replace with a similar working transistor. If not, then do comparisons between the good and bad channels.Although schematics can be helpful, you have the benefit of a working example as reference. You'll probably find the culprit with a little sleuthing.
Iron stand for Hakko FR301 - Page 1
Forum section: electronics / repair

author: tkamiya
author_rank: Super Contributor
timestamp: July 02, 2018, 11:56:55 pm
content: I guess this one belongs in "repair" section....But more of a repair tool, and desoldering gun to be exact. I just bought a Hakko FR-301. What a difference in results when compared to (just returned) Chinese copy for 1/3 of the price. Simply stated, Hakko works and the other didn't. It didn't have enough heat or suction.Anyway, I'm pretty sure many people have this model. What iron stand do you use? This one has everything built in to its handle so it's rather tail heavy and tall. It needs suitably tall and heavy duty stand. Can someone give me a suggestion?

author: particleman
author_rank: Regular Contributor
timestamp: July 03, 2018, 12:42:55 am
content: Quote from: tkamiya on July 02, 2018, 11:56:55 pmFor my hakko 808 I use the hakko 633

author: I_Code_4_Hugs
author_rank: Newbie
timestamp: July 05, 2018, 03:26:35 pm
content: Quote from: particleman on July 03, 2018, 12:42:55 am+1 for the 633.Quote from: tkamiya on July 02, 2018, 11:56:55 pmI have a FR-300 and if you're OK with resting the handle on your bench with the power cord overhanging, then the 633 would work:

author: tkamiya
author_rank: Super Contributor
timestamp: July 05, 2018, 10:44:39 pm
content: Thank you. I just took delivery of 633. It would have been nice if Hakko produced a proper stand that fits the sucking iron. A little sheet metal "thing" came with the iron but it's not even a good joke.
Solid state Amp Schematics WH300 - Page 1
Forum section: electronics / repair

author: antmaz
author_rank: Newbie
timestamp: July 05, 2018, 09:22:03 pm
content: Hi all,I was wondering if anyone could recommend a good site for amplifier circuit diagrams. I have a Randall WH300 Solid state guitar amplifier, and have some issues with the amp. I've had a hard time finding a schematic for it, and want to find one before I take it apart. Any help would be greatly appreciated, thanks in advance.Anthony
Teardown & Repair of an Agilent E4440A 3Hz - 26.5GHz PSA Spectrum Analyzer - Page 1
Forum section: electronics / repair

author: Hugoneus
author_rank: Frequent Contributor
timestamp: July 04, 2018, 07:25:51 pm
content: You can watch the video here: [21 Minutes]youtu.be/7YYcO-xkmO4More videos at The Signal Path:www.TheSignalPath.com

author: Samogon
author_rank: Frequent Contributor
timestamp: July 04, 2018, 11:04:38 pm
content: I think no chance to repair those relays even after you torn one open.

author: texaspyro
author_rank: Super Contributor
timestamp: July 05, 2018, 02:19:19 am
content: One should never handle watch/memory batteries with bare hands. The oils and salts in a fingerprint across the cell can discharge the battery faster than the circuit. I also always clean my cells with IPA before installing.

author: TiN
author_rank: Super Contributor
timestamp: July 05, 2018, 04:43:56 am
content: I think Hugoneus confused a little pinout on relay when talking about it. Coil drive pins are on same side as center "RF input" contactNice video, I add vote comment to see video on how to simulate RF components in software. Are there any "hobby"-level RF field simulators?.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: July 05, 2018, 05:15:25 pm
content: Quote from: TiN on July 05, 2018, 04:43:56 amI think you might be right about the pins.I was traumatized about my tool breaking.Haven't found a good hobby 2.5/3D simulator yet.
Grounding Output of AC/DC PSU - Page 1
Forum section: electronics / repair

author: ed_reardon
author_rank: Regular Contributor
timestamp: July 02, 2018, 11:54:14 am
content: Hello all,In the work life I've been handed an issue with an instrument.The instrument is powered by a (transformer) isolated DIN rail switch-mode PSU and it's been reported many of them are floating well above ground (sometimes around 80VAC) - my initial instinct is to tie 0V PSU output to mains referenced earth, which has been tried on test equipment and certainly stops the floating issue (and the odd nibble from the damn things), as it is expected to.However, with isolated PSUs (they're not my area!) is there anything inherently wrong with doing this? They're clearly no longer entirely separated but as the whole installation is well earthed so that isn't an especially great concern to me.As an aside, and I've spent the morning trying to work though out, these instruments are measuring from sensitive electrodes in to instrument amplifier circuits, the input (and subsequently output) appears much more stable with the PSU 0V to Ground, which is the opposite of what I expected?!Am I going mad or is this plausible?

author: Jeroen3
author_rank: Super Contributor
timestamp: July 02, 2018, 12:21:17 pm
content: Every isolated AC/DC converter has leakage current. This leakage current will find a way.Through your sensors perhaps? Messing up the measurement.In general, any DC bus in an system should be grounded, unless there is a specific requirement not to. Low leakage power supplies should be used in that case.

author: Relayer
author_rank: Contributor
timestamp: July 04, 2018, 11:15:37 pm
content: Hello ed_reardon,If you're talking about the primary of the power supply, then you cannotconnect earth directly to it. It is designed to float.Does the mains plug have an earth pin?If not, then to reduce the tickles you may receive when touching any ofthe metal parts, is to replace the mains cord with a 3 pin one that hasan earth wire within it, then place the active and neutral wires in thenormal place, then connect the earth wire to a 22nF 275V X2 capacitor(0.022μF), and the other side of the cap to the earthed metal work.This should stop or greatly reduce any zaps you may encounter.Regards,Relayer
Dell BIOS programming - Page 1
Forum section: electronics / repair

author: rdagger
author_rank: Contributor
timestamp: July 06, 2018, 04:54:57 pm
content: The Dell update utility crashed during a bios update and bricked my Vostro 410 PC. Dave’s HP envy repair video inspired me to take a shot with a TL866 programmer. The Dell DG33A01 MB has an MX25L8005 CMOS serial flash chip and there is an SPI port. I traced the pins and connected the ICSP cable. Initially I got the same damaged error that Dave received and addressed it in kind by applying 3.3V from an external supply. This cleared the error but unfortunately the Chip ID is reading FF FF FF. I tried swapping MISO and MOSI but it just changed the ID to 00 00 00. I tried bypassing the chip ID but reading and programing doesn’t work. I added a 22pF cap between MISO and ground but that didn’t help. The battery was removed and tried all jumper possibilities. Any suggestions?

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 06, 2018, 10:27:01 pm
content: It is hard to follow without linking to the trouble "Dave" ran into.I've never had trouble recovering corrupt SPI flash BIOS, but I do the programming out of site.My programmer is a Xeltek SP500P the recommendations for use are to add 30pF capacitors between SO and /CS to ground, I have found this to often be needed.For ISP they also recommend adding a bypass capacitor of 20 to 100nF (Vcc-GND across I.C. or SPI header) .Once you have been able to flash, think of replacing battery and CLRCMOS jumper in the right position.Hope that helps.

author: rdagger
author_rank: Contributor
timestamp: July 06, 2018, 10:36:22 pm
content: Quote from: shakalnokturn on July 06, 2018, 10:27:01 pmHere thelink.I did try the SO cap. I'll try the CS and bypass caps tonight.

author: wraper
author_rank: Unknown
timestamp: July 06, 2018, 10:41:59 pm
content: Quote from: rdagger on July 06, 2018, 04:54:57 pmDon't waste your time and just desolder it. It's common that another IC which is not powered pull data pins to GND through built in ESD protection diodes.QuoteDoes not matter when programming in circuit, there already should be a bypass cap on the PCB.

author: rdagger
author_rank: Contributor
timestamp: July 06, 2018, 10:55:56 pm
content: Quote from: wraper on July 06, 2018, 10:41:59 pmWasting time is kind of my hobby, but desoldering is my backup plan. I don't get why they would put a SPI header on the MB if you can't use it.I guess I can hook up the data pins to my scope which has a SPI decoder.
Fixing a toy drone - Page 1
Forum section: electronics / repair

author: jdraughn
author_rank: Regular Contributor
timestamp: July 03, 2018, 01:49:27 pm
content: I actually was able to fix it by going through the calibration procedure on page 5 of the manualhttp://www.udirc.com/wp-content/uploads/2017/01/U818A-1guide.pdfBoy am I embarrassed, another RTFM thing. So please disregard what I posted.Hi, someone has asked me to take a look at children's toy drone and wanted to get some thoughts on what the problem probably is. When the throttle is at 0, nothing turns (which is intended behavior), but as soon as you start giving it a tiny bit of throttle, two of the blades which turn counter to each other start running at what appears to be 100% on while the other two turn very slowly, which is appears to be caused by the air generated by the other two props. The two props which go to 100% are the front two props and cause the entire drone to want to move backwards. If I give it 100% full foward stick (right stick forward), which should give power to the other two props and slow down the front two, appears to make no difference. Tilting the drone forward or back appears to make no difference either in the speed at which the front props move compared to the rear two props.The only way I can get the drone to react to the controls is to give the right stick full right or full left, which I can feel it wanting to tilt left or right, but the rear props still appear to be turning by just the movement of air generated by the front two props which appear to be moving at 100% (I can only guess that one of them is slowing down a little bit to get it to tilt that direction.)I have checked the trim settings, all 4 props seem to spin freely when spun by hand, and I don't see any mechanical problems. I also double checked and all the props are all installed correctly on their corresponding motors.What I can deduce by this is that the problem is probably related to the gyro and the controller thinks it's tilted forward so it's compensating by running the two front props at 100%. The drone in question is a u818a-1-p and the receiver, brains, speed control and gyro are all integrated into 1 unit. I have not yet taken it apart yet to see if I can get the model of the gyro so I can start probing with my oscilloscope.I'm guessing that if the gyro does not output analog voltages for each axis, then it's using a serial bus. If it's using a serial bus then the gyro is probably damaged, if it outputs analog voltages then possibly there is a short or something causing the bad axis to go to either rail, or the gyro is damaged.Am I on the right track here?
HP8595E MIXER ? ? - Page 1
Forum section: electronics / repair

author: jean françois
author_rank: Contributor
timestamp: June 18, 2018, 09:51:38 am
content: Hello,Thank you for helping me,with my HP8595E I encounter the following problem "cal signal not found".I measured with a hp435B the 300MHZ -20dbm is perfect.On the first range of the mixer 5086-7952 up to 2.9GHZ the measured levels are completely false.Depending on the frequency it can miss -40dbm.From 3 GHZ the measured levels are about good and perfect the more one goes up frequency.Can we think that the 1st Mixer 5086-7952 has broken down? ?I forgot to reconnect the DCblock on the input.can I use the 8590 Series Service Manual to dismount the RF part?I can not send this device for maintenance.Please, thank you for your future answersJeanfrançois

author: Gixy
author_rank: Regular Contributor
timestamp: June 18, 2018, 09:38:29 pm
content: Hello Jean-François,You can try to contact Christian Couderc at voilelec.com, he probably can help you.(https://www.voilelec.com/voilelec/index.php/component/k2/item/509-analyseur-de-spectre-agilent-hp-8595e).Denis

author: jean françois
author_rank: Contributor
timestamp: July 03, 2018, 09:01:36 am
content: Hello,thank you for your answer, I will try to contact Christian couderc who is ham radio like me elsewhere.in any case thanks for the information.Jean François F1xxx.
Diode replacement help - Page 1
Forum section: electronics / repair

author: dark_hawk
author_rank: Regular Contributor
timestamp: July 03, 2018, 05:38:13 pm
content: Hi,I’m trying to replace a broken T4 diode that got destroyed while I was assembling the device. The device is the circuit board of an electronic cigarette.Picture of the diode elsewhere on the board.That T4– I think – was in the screen driving circuitry of a 1 inch black and white oled, because when it got broken the screen turned off while the device was working fine without the screen.I don’t have that same diode for replacement, so I’m trying to decide which part should I replace it with and learn something new doing so.The voltage across the diode is 0.5v when the screen is on and 2.5v when the screen is off.I replaced it was this:and the screen worked, but the problem is it’s a different size and the diode is hanging in the breeze and any it can easily come loose.I also replaced it with this and it’s working fine :Here it is soldered in its place.My replacement options are the two diodes above and the following:My question is, which of those will be the closest replacement for the T4 diode.Thanks.

author: envisionelec
author_rank: Frequent Contributor
timestamp: July 03, 2018, 06:53:00 pm
content: T4 is a 1N4148 diode in a SOD-123 case. The others appear to be a different type.BAV16W is a correct replacement.https://www.digikey.com/product-detail/en/diodes-incorporated/BAV16W-7-F/BAV16W-FDICT-ND/717826
Fluke 8846A - Fuse instantly blows - Page 1
Forum section: electronics / repair

author: mdszy
author_rank: Unknown
timestamp: July 02, 2018, 03:01:00 pm
content: I have a Fluke 8846A that I'm repairing and the problem it's having is when I power it on, the fuse instantly blows. I've verified that there isn't any problem with the transformer since I used the transformer from another unit and it still blew the fuse. I'm kind of stuck on how to troubleshoot this, since I can't actually power the unit on to test voltages and such, and the power supply is part of the main circuit board, not its own separate unit.Any pointers for where to start looking or suggestions for troubleshooting steps?

author: GreyWoolfe
author_rank: Unknown
timestamp: July 02, 2018, 04:19:45 pm
content: A dim bulb tester should help with that. Google Fu will give plenty of examples.

author: mdszy
author_rank: Unknown
timestamp: July 02, 2018, 04:23:36 pm
content: Quote from: GreyWoolfe on July 02, 2018, 04:19:45 pmOh nice, thanks. I was thinking using a variac could be useful, but I don't have one and don't particularly want to spend the money on one. But this looks like an awesome alternative that I'll try out tonight hopefully. Thank you!

author: ArthurDent
author_rank: Super Contributor
timestamp: July 02, 2018, 06:38:50 pm
content: I don't have a 8846 but the EEVBlog has a video of a teardown that might help. If you have another working unit you got the transformer from there are some other things to check. I'm assuming you had replaced the fuse with the correct value with the voltage selector set correctly and all the push-on connectors on the fuse/input assembly from the transformer primary are in their correct location.There appear to be separate connectors to the circuit board from the transformer primary and secondary. If you unplug the larger connector from the secondary and plug the power cord in and turn the power switch on and it doesn't blow the fuse, the problem is on the circuit board. The most likely suspects are diodes and filter caps. Look for discoloration on the board and signs of leakage/bulging on the caps.Test and replace any diodes that are shorted or caps that are leaky. Because it is blowing the fuse instantly I'd suspect a bad diode that is shorting out a secondary winding. A good hand multimeter should be able to identify a shorted diode in circuit so try this first before removing random parts. Caps often (but not always) fail open and would cause other problems and not blow a fuse. Generally problems like this are power supply related and replacement parts are readily available and cheap.Here's a photo of the power supply area I copied from the teardown.http://www.siliconvalleygarage.com/eevblog/8846teardown/supplies.JPG

author: mdszy
author_rank: Unknown
timestamp: July 02, 2018, 06:41:05 pm
content: Quote from: ArthurDent on July 02, 2018, 06:38:50 pmGreat! Thank you so much for the tips. I'll check all of this stuff out!
1980s Sanyo RM 6400 Clock Radio - Page 1
Forum section: electronics / repair

author: jt154
author_rank: Newbie
timestamp: July 02, 2018, 10:07:33 am
content: Hey guys, first time posting here. I’ve recently acquired a Sanyo RM 6400 Clock Radio from a flea market that needs repair.Everything is working except for alarm 1. When alarm 1 is set to radio, the radio comes on as it should. However, when it is set to buzzer, the radio comes on and instead of the buzzer, a popping sound is emitted from the speaker when the volume for the radio is set on minimum.When I first got the clock radio the buzzer worked, but after one week of storage it has miraculously died. I suspect the TMS3459BNL chip might be to blame, but I’m hoping the problem might be something less costly as the cheapest chip I could find costs more than what I paid for the clockWould anyone have any schematics or manuals? I couldn’t find any online. Greatly appreciate any help.

author: envisionelec
author_rank: Frequent Contributor
timestamp: July 02, 2018, 02:08:09 pm
content: When I was young, I would test my repair skills on clock radios. I had one exhibit behavior that was very similar to this. I could never find the problem, but chalked it up to lightning damage - here's why: the FM-band antenna is usually coupled to the AC line cord. A high energy spike generated from a nearby lightning strike can easily induce a current into the antenna and convert to a massive energy pulse across the PCB and damage the microcontroller.These were generally disposable items, even in the 1980's...

author: jt154
author_rank: Newbie
timestamp: July 02, 2018, 02:13:01 pm
content: Quote from: envisionelec on July 02, 2018, 02:08:09 pmI desoldered all of the electrolytic caps to measure their values, seems like some are gonna need replacing. Hopefully that will fix the problem.I have2 radio clocks, one of them is the Sanyo (which is my favorite), the other is a Philips D3200. The Philips units works fine except that someone cut off the antenna wire so I’ll have to solder a new length of wire for that and it should be fine.
Dyson DC35 Handheld Vacuum Cleaner Not Starting - Page 1
Forum section: electronics / repair

author: jedimindtime
author_rank: Newbie
timestamp: June 30, 2018, 05:48:46 pm
content: Hi!So I'm looking for some guidance for my quest to troubleshoot and hopefully repair my Dyson DC35 Handheld Vacuum Cleaner that is currently out of commission due to the motor not engaging.As for the battery;I have plugged the battery into another DC35 and it works fine.I plugged the battery from that DC35 into mine and the issue is the same.Switches;I have also checked and made sure that the filter/safety switch is engaging.Power is also getting to the motorised head attachment as the roller spins when pressing the trigger.L.E.D's;When I press the trigger the main LED doesn't turn on, but if the 'MAX' mode is on, the ring light/LED surrounding the 'MAX' button turns on when I press the trigger.It just seems like everything works but the main motor is not engaging, there are no noises when trying to start it, no 'burnt' smells or obvious signs of any point of failure (that I'm aware of)I can provide pictures and any other info if need be, but I would much rather learn how to find out myself than to be told the answer, so if anyone could please assist me in figuring this issue out, that would be awesome!I just don't know where to start, or how and what to test for etc.Even though they look o.k, would the 2 'large' electrolytic capacitors, which I'm guessing are used to start the motor initially, be the best starting point?The whole main unit is disassembled at the moment, the cover is very difficult to take off once it's clipped back together.In terms of test equipment I own;I have a really crap DMM (Jaycar kit I put together years ago), a 2nd hand 'Fluke 75' that I just bought but needs a bit of work to get it going. That's pretty much it. No oscilloscope or ESR meter or anything, do have a bench power supply if that's useful at all. I am in the market for a new decent multimeter, but my current financial situation makes things very difficult if not impossible.I may be asking a lot, but i'd very much appreciate any help at all, nothing's too insignificant.Thanks for your time reading my post.Cheers!

author: SMdude
author_rank: Frequent Contributor
timestamp: June 30, 2018, 11:30:35 pm
content: Photos would be most handy.But, first I would be checking to see if anything happens at the motor when the trigger is pulled.Then work your way back.However, being Dyson, it is probably no normal dc motor you are dealing with!Be careful, there could be high voltages about.. To get an idea of the voltages, look at the voltage rating of any of the caps you can see.

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 30, 2018, 11:47:14 pm
content: It's a brushless electronically driven motor.
Replacement for HP 8555A Spectrum Analyzer 100V-26.1V Buck Converter  - Page 1
Forum section: electronics / repair

author: Jamie_A
author_rank: Contributor
timestamp: June 29, 2018, 12:03:22 am
content: I'm currently in the middle of a repair for my HP 8555A 18GHz spectrum analyzer.Luckily, I got it with it's operating and service manual, and quickly used it to isolate the problem. The 8555A has a bizarre power distribution design. It takes in 100Vdc, uses a 100V-26.1V buck converter to drop down the voltage, and then linearly regulates that to 20Vdc and 10Vdc. The supplies were all reading about half of their expected voltage values. By removing the linear stage, and substituting it for a constant current dummy load, I saw the 100V-26.1V buck converter drop to 17V output under it's rated load. After putting the linear stages back in and substituting the buck converter for a lab supply, the unit came back to life!I had no idea switch mode supplies were in used back in the 70s, and it seems they got this module wrong on the first try. My 8555A is an earlier model, and a few years after it's release they swapped out this switch mode supply for a completely different design due to failures (they even recommending replacing it in the manual). Mine has a number of blown ICs and diodes. The caps check out fine with my ESR meter though.With that said, I'm not going to bother replacing these parts if the design might fail in the future. I'm fine buying a DC/DC module, or designing my own, but I'm having trouble finding options in this weird voltage range. TI has some nice IC like the LM5161, but that has an absolute maximum input of 100V. There's also the AD LTC7138, which maxes out at 140V.Does anyone have recommendations on how to approach this? I've done DC/DC designs in the past, but never something this high voltage. Any off the shelf options I'm missing?
Keithley 2400 Display for Keithley 2420 ? - Page 1
Forum section: electronics / repair

author: JohnPi
author_rank: Regular Contributor
timestamp: June 27, 2018, 04:17:29 am
content: I was asked to repair a Keithley 2430 at work - its display doesn't turn on. We have a non-functional 2400 available. Before I open the 2430, does anyone know if the display boards in the 2400 and 2430 are the same ?Of course I'll check for just ribbon cable failures and similar mechanical issues also.

author: TiN
author_rank: Super Contributor
timestamp: June 27, 2018, 04:40:26 am
content: Yes, they are same.

author: JohnPi
author_rank: Regular Contributor
timestamp: June 28, 2018, 02:00:48 am
content: That worked -- now I have one good 2420 (it's not a 2430 as in the title originally), and a bad 2400 -- the bad 2400 doesn't even appear to turn on now -- does it need the display to be able to turn on ?
Troubleshooting an old Dell laptop - Page 1
Forum section: electronics / repair

author: vNawar
author_rank: Newbie
timestamp: June 26, 2018, 03:09:12 pm
content: HelloI found this old Dell laptop and thought maybe I could learn something or two from trying to repair itso tried to power it on (without battery), but when I pressed the power button the laptop seemed to start up at first but then nothing happened, no lights and nothing on the screenand when I unplugged it I think I could hear it shut offanyway I took it apart to see what could the problem be and I saw this on the motherboardhttps://imgur.com/a/UipvHUhwhat is this weird fluid thing? it's coming out of what I think is capacitors and these three-legged components and the fan portis it permanent damage or could it be fixed?

author: Rasz
author_rank: Super Contributor
timestamp: June 27, 2018, 10:48:28 am
content: "this old Dell laptop" is a very popular modelits core2, worth ~$15-20 when 100% working, yours appears to have suffered retard with a heatgun to the GPU, its a source of soldering practice and parts (connectors/transistors/resistors) at this point
HP 34401A ERROR 621 AND 622 - Page 1
Forum section: electronics / repair

author: arturo
author_rank: Newbie
timestamp: June 26, 2018, 08:54:12 am
content: DearI can not read the alternating signal on my multimeter and I get errors 621 and 622 please someone who can help me thanks

author: Zucca
author_rank: Unknown
timestamp: June 26, 2018, 02:43:47 pm
content: Ciao Arturo,download the service manual, open the device and do some measurement. Post here your results.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 27, 2018, 07:03:48 pm
content: Always start with measuring the power supply rails.Many times a problem can be found there.
HP 1740A scope no trace fix - Page 1
Forum section: electronics / repair

author: ddelectrical
author_rank: Contributor
timestamp: May 21, 2017, 05:01:05 pm
content: Hi all, great news! My HP1740A scope had a missing trace. I finally found that Q3 on the Vertical amp board, A5, was open circuit. I replaced it with a 2N3906, (e and b legs crossed and insulated as the pin config is different to original), and it works fine. The original transistors were marked with HP in house code and was, I think, a 20V pnp. The 2N3906 is a 40V type and works well. Trace is crisp. hfe original = 180, hfe new part = 300.The hybrid unobtainium alien technology ic's are both fine!There are quite a few threads here on this problem so I hope this points to a cure for those with the same fault.All 4 transistors in the main vert amp are now the same type. It is possible that the original ones had a slightly higher frequency rating but these new ones are 200MHz rated and this is good for most of the work I will be doing with this scope.BEWARE: the picture in the service manual shows A5Q3 in the wrong orientation!!!! If you look closely at the actual pcb you will see a little symbol of the correct position for this component. A5Q1 is correct.If one or both of these transistors has shorted the section in the manual about using external trigger view to ascertain if pre or main amp has failed does not apply. In my case one was open cct so no visible trace could be seen anyway.Note: replace both transistors if one has failed to ensure trace balance.Good luck!

author: stellarpower
author_rank: Newbie
timestamp: June 27, 2018, 06:24:55 pm
content: Hi there,I'm new here and think I have the same problem with my scope, I was wondering whether I should start a new thread or post here, please could you tell me which would be preferable?By no trace I assume that you have a scanline but no vertical deflection, is that right? Mine starts up okay, (there's a metallic click on first power on though, not sure about that), but after about a minute there's no trace and neither of the vertical position pots will budge the trace. My electronics knowledge is a few years old and really basic, I actually bought the scope as I thought it'd help me learn better but it had this error intermittently a few years ago, has been sat in a cupboard since, and now I have a project for which I need it, it's non-functioning!Thanks for your help!
HP1740A Delay Calibration - Page 1
Forum section: electronics / repair

author: tombi
author_rank: Regular Contributor
timestamp: June 24, 2018, 01:16:38 pm
content: Hello,I have a very annoying problem with a 1740A. The unit had a couple of minor faults that I repaired but now I am trying to calibrate it and stuck on a step.Adjustment step 5-51 has you set the delay to 0.2 and then line up the bright dot (delayed timebase dot) with the small graticule 2mm from the left by adjusting A7R169Unfortunately I have A7R169 at the minimum and I can't get it there. It is only slightly off (maybe 2mm - one minor graticule line).So should I be able to adjust the delay to zero or is there supposed to be a small gap? I would think I should be able to if a delay of 0.2 is supposed to set it to 2mm from the start. Anyway I can't and the offset seems relatively consistent across the screen.I checked TP4 on A7 and the voltage is around 0.9 or 0.8 when the delay is turned to zero. The manual indicates it should be 1.3 to 11.3 so this seems already lower than they expect.The sweep signal looks a little low in that it starts at about 800mV. I thought this might be why this is happening.So I followed the setup on the A8 schematic and stopped the sweep to take voltage measurements. They are mostly ok except that collector of Q3/Q13 is -1.5V instead of 1V as indicated. I checked other places like Q4 and Q7 and these voltages look mostly ok. TP2 is right also.C11 had been replaced on A8 before I got the unit. I replaced it again (with a 100uF capacitor as the previous person put a parallel combination of around 63uF in). Otherwise I've not changed anything here.I checked the opamp and that manages the integration loop and it looks Ok (inverting/non-inverting voltages match).Any idea where to look? Is that -1.5V likely to be the cause? If so what might be the cause of that?So service manual ishereThanks,Tom

author: David Hess
author_rank: Super Contributor
timestamp: June 24, 2018, 03:01:34 pm
content: If the delay is calibrated like Tektronix does it in most cases, then the delay's mechanical dial is suppose to be offset from the 10 turn potentiometer's "zero". Not coincidentally the offset is suppose to be about 0.2

author: tombi
author_rank: Regular Contributor
timestamp: June 25, 2018, 01:26:00 am
content: Ok are you thinking this could be a mechanical issue?I have an old 475 actually and the 1740 dial is different - On the 1740 when you turn it to zero, the outer dial zero is half a value out. When you turn the inner dial to the 1 position the outer dial clocks to zero. Also when you turn the inner dial round a turn, the outer doesn't clock to 1 until the inner gets goes past 9 and gets to zero.This makes me think the knob may have been removed and re-installed incorrectly.Thanks - that sounds like a good line of inquiry to follow!Tom

author: tombi
author_rank: Regular Contributor
timestamp: June 27, 2018, 03:47:08 pm
content: BTW - I gave up. The delay is basically 0.1 out (I adjusted it to be exactly 0.1 out).I completed the rest of the calibration procedure with no issue and the scope is functioning pretty well.So I am calling it done.Tom
spectrum analyser   HP8595E - Page 1
Forum section: electronics / repair

author: jean françois
author_rank: Contributor
timestamp: June 27, 2018, 01:59:18 pm
content: Hello dear friends, I call you to help,the 5086-7952 mixer on my 8595E spectrum analyzer 7GHZ is broken.in the first range.I have a mixer 5086-6821 (same range frequency 7GHZ in good condition.it seems that the technical characteristics of these two mixers is very close.while waiting for better days, and even if the amplitude is wrong, can I mount it instead of 5086-7952.?For the moment, I can not do otherwise.thanks in advance,Alain
any fluke nettool serie 1 or 2 user here ? - Page 1
Forum section: electronics / repair

author: kripton2035
author_rank: Super Contributor
timestamp: June 27, 2018, 07:42:59 am
content: Hi folks,I just bought one fluke nettool serie 1 and one serie 2 used.it seems Fluke did not keep any firmware for these old gears (well they are of this century at least ...)and I have some defect on them I would like to try to flash these devices again.problem I don't have any firmware, Fluke cannot help me tooand I don't have the nettool uploader program too...please feel free to contact me (in private if you want) if you have any information on how I could do that operation.thanks.