hybridfree/eevblog-posts huggingface dataset:
Help with PC motherboard component - Page 1
Forum section: electronics / repair

author: 4cx10000
author_rank: Regular Contributor
timestamp: March 07, 2021, 04:44:02 pm
content: Hi!Suddenly the motherboard IPM17-DD HP Envy gave up. I pulled the cover, swapped the PSU but to no avail. I then took my thermal imager and found that an ic, next to the ATX power connector, was running hot by more than 100 degrees C. I have two pictures of this IC (3x3 mm) which I have not found on the webb so I would be very thankful if someone know what it is. By chance, do anyone know where to get hold of a schematic for this motherboard?Thanks in advanceBjorn

author: wraper
author_rank: Unknown
timestamp: March 07, 2021, 04:46:11 pm
content: RT8237EZQWhttps://datasheetspdf.com/pdf-file/1346014/RICHTEK/RT8237E/1

author: 4cx10000
author_rank: Regular Contributor
timestamp: March 07, 2021, 05:02:17 pm
content: WOW! Thank you so much wraper! How the he... could you find it so fast?!I can clearly see the marking information in the datasheet but I searched all over the webb, with every thinkable option, and with no hits at all!Thank you once again wraper!

author: mariush
author_rank: Super Contributor
timestamp: March 07, 2021, 05:32:18 pm
content: Check ceramic capacitors and mosfets and diodes around that chip ... it may gave failed after another component around it failed.

author: wraper
author_rank: Unknown
timestamp: March 07, 2021, 05:47:10 pm
content: Quote from: 4cx10000 on March 07, 2021, 05:02:17 pmI googled "88 richtek" because it looked like Richtek.
Help with PD78C12ACW-675 microcontroller from a Tascam Portastudio recorder - Page 1
Forum section: electronics / repair

author: faxika
author_rank: Newbie
timestamp: February 01, 2024, 03:01:59 am
content: Hello,I`m trying to bring back to life a old Tascam Portastudio 464 which have this microcontroller in it that control the commands to actuate the motors, LCD screen and recording signals.So, Im having an issue that it only plays for a little bit and for some reason the microcontroller gives a signal to STOP the machineI`m suspecting that the microcontroller has been shorted by someone before, but I don`t know how to diagnose thisSince I don`t know much about digital eletronics, maybe you guys could shine a light to me in these readings I made from 2 pins (one from ALE pin and other from MODE1 pin) that looks weird to me. I attached pics so you guys could see.As far as I read the microcontroller manual, these pins should be just a HIGH or LOW signal, not a bunch of noisy and scrambled signal, or Im wrong?Theres no component attached to these pins that haven`t passed an eletronic test, they look good, thats why im suspecting that the microcontroller is bad, but I never fixed something with digital eletronics, I only repaired analog eletronics so far.
Help with Pioneer SX-S30 - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: July 14, 2022, 09:01:23 pm
content: I am looking for a service manual and/or schematic for a Pioneer SX-S30.I am having trouble with the switch mode power supply. I have 3v 12v and 33v voltages on one section of the board but the voltages do not appear at the connector for the FL tube display. I have attached some photos of the PS board. If anyone could email me a copy of the service manual or schematic, I would appreciate it.If not, maybe someone has experienced a similar problem and could help me find the problem. I have traced the voltages to one portion of the board and marked the photo showing where the voltages are missing. Transistors? Q923, Q924 and Q925 seem to test open on my DMM. Since the transistors are small surface mounts and I can not see the markings on them, maybe someone could identify them for me.I will have to attach photos one by one because of size limit.Thank you very much.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: July 14, 2022, 09:09:21 pm
content: Here is photo two:

author: Bargainhunter
author_rank: Regular Contributor
timestamp: July 14, 2022, 09:10:50 pm
content: Here is photo 3

author: Bargainhunter
author_rank: Regular Contributor
timestamp: July 14, 2022, 10:31:12 pm
content: Here is the last photo:

author: Bargainhunter
author_rank: Regular Contributor
timestamp: July 15, 2022, 02:08:47 pm
content: Here is a list of smd components that I need to know what they are:Q901, Q907 cy O 620Q912 OB COQ913 LG or LC (not sure)Q914 UAQ922 SGQ923, Q924, Q925 NB C1Can anyone tell me what semiconductors they represent?Thank you.Chuck

author: gamalot
author_rank: Super Contributor
timestamp: July 15, 2022, 04:19:53 pm
content: I can only give some unsure guesses:Q901,Q907 2SJ186https://datasheetspdf.com/pdf-file/201816/HitachiSemiconductor/2SJ186/1Q912 KRA102Shttps://datasheetspdf.com/pdf-file/1145667/Kexin/KRA102S/1Q913 2SC2712-GRhttps://www.mouser.com/datasheet/2/408/2SC2712_datasheet_en_20140301-707731.pdfQ914 MMBTA517https://datasheetspdf.com/pdf-file/1018702/KEC/MMBTA517/1Q922 2SA1162-GRhttps://html.alldatasheet.com/html-pdf/29946/TOSHIBA/2SA1162/246/1/2SA1162.htmlQ923, Q924, Q925 KRC102Shttps://datasheetspdf.com/pdf-file/514852/KoreaElectronics/KRC102S/1

author: Bargainhunter
author_rank: Regular Contributor
timestamp: July 15, 2022, 04:22:41 pm
content: Thank you very much for your suggestions.I will compare the datasheets to see if they could be the correct part numbers in the circuit.chuck
Help with plastic capacitor identification please - Page 1
Forum section: electronics / repair

author: tony359
author_rank: Frequent Contributor
timestamp: February 10, 2025, 06:46:47 pm
content: Hi there,I'm trying to fix a modular power supply from XP Power. The offline switcher (a TOP242 for the 5VSB I think) has blown and I'm replacing components which look burnt.One is the white capacitor you see in the attached picture, from another board. It reads 10nF and it's made of plastic. I didn't realise it was made of plastic so when I went to clean the solder from the good part, I unintentionally melted it a bit.Can someone point me to what type of capacitor that is? I believe this is part of the snubbing network of the offline switcher so I'd imagine it's rated 400V.Thanks!

author: wraper
author_rank: Unknown
timestamp: February 10, 2025, 06:51:53 pm
content: It's SMD film capacitor. Looks like snubber capacitor, certainly rated for more than 400VDC, most likely 1000+V. I see no damage on the photo.

author: tony359
author_rank: Frequent Contributor
timestamp: February 10, 2025, 08:22:00 pm
content: Thanks!That's the undamaged one from the good board. I removed it to measure it and read 10nF. Then I insisted with some de-soldering wick too much and... The one on the board with the exploded offline switcher is discoloured but still good. But I'll order some and replace them.You're right, the datasheet also says 1kV, I looked at the wrong picture.I had a look at Mouser and Digikey and I was unable to find a 10nF, 1kV smd film capacitor in stock. On Mouser the only one available - but not in stock now - is the belowhttps://www.mouser.co.uk/ProductDetail/KEMET/LDEQE2100KA5N00?qs=FE4FjJMnrEJMiX46HK8n7g%3D%3DAm I looking in the right place?Thanks for your help!

author: eurgenca
author_rank: Regular Contributor
timestamp: February 12, 2025, 06:50:14 am
content: Here you go.https://uk.farnell.com/kemet/ldeqe2100ka5n00/cap-0-01-f-1-kv-10-pen-2824/dp/2446205?srsltid=AfmBOopWSQkzj0jZ3f_mTZ48ftu69H6galLOGnbb3b6yzZrM_kec5QPU

author: tony359
author_rank: Frequent Contributor
timestamp: February 23, 2025, 09:47:17 am
content: Thank you! I got some - they're bigger but I think the pads should be big enough to accommodate themCheers!
help with regulator  - Page 1
Forum section: electronics / repair

author: vixo
author_rank: Regular Contributor
timestamp: February 27, 2020, 04:54:22 pm
content: im fixing an old piece of musical equipment for a friend. I have the schematic, but it turns out the schematic doesn't follow what I have in front of me. The device is powered by two 9volt batteries in series, but the 'ground' is derived from regulators. I'm seeing that the positive power rail is very close to the negative, so I investigated the power section and disconnected the power from the main circuit to make sure nothing in the circuit was affecting it - no change - so I started looking at the circuit itself and discovered that it's not the same as the schematic but actually has two PNP 2N3906's (figure 1) instead of the schematic (figure2) MPSA14. This doesn't make sense to me - shouldn't that type of darlington pair be used *the other way up*? I can't understand how it is supposed to work. To add more confusion, in simulation (figure 1) it seems to work fine, but in the piece of equipment AND when i breadboard it, it does the same thing - the rails are about 0.2 volts away from each other.can anyone shed some light on this? Should this work, or what??this is the entire schematic that I have :http://clacktronics.co.uk/research/drumlab/star-synare-3/Clacktronics_Star_Synare_Schematic.gif
Help with resurrecting an analog scope (moved from another section) - Page 1
Forum section: electronics / repair

author: pitpat
author_rank: Contributor
timestamp: May 12, 2020, 03:11:34 pm
content: Hi, im not super good with english so be kind.I got for these quarantine days a cheap Hameg 103 to be restored.I'm quite new with old school tech, anyways the thing is when i first got it everything look'd ok but after a few minutes of playing with the test trace all went black (or white since we are talking about crt).The strange thing is that the component tester is working good, vertical line for short-circuit and L-shaped line for diodes.After replacing some caps that wasn't quite in specs anymore (only the few that i had laying around) in normal mode i got a dot that i can move with the x-y position knob.The big resistors of the y final amp gets really toasty.Since the component tester isolate the y-preamp board i would say that the fault can be located in there.What do you guys think?i'll leave the service manual for referencehttps://cdn.rohde-schwarz.com/hameg-archive/HM103_englisch.pdfThanks.

author: pitpat
author_rank: Contributor
timestamp: May 12, 2020, 03:17:46 pm
content: little update: all the ceramic 0.1uf cap on the main board seems to be cracked.
HELP with Sencore PA81 connectors - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: January 27, 2021, 05:37:15 pm
content: My previous posts have not been showing up. I will try again.I'm having trouble with the connecting plugs on the pc boards. The wires are connected to the plugs by pushing the wires down between a "v" shaped pin on the plug. This is supposed to "bite" into the wire making contact. This is similar to telephone wire connectors. However once the wires come off, it's nearly impossible to re-attach the wire(s) to the plugs. I have attached some photos as an illustration. Has anyone solved this problem? Are there any replacements that use solder connections to the plugs that will fit the headers on the boards?Any help will be greatly appreciated.Thank you.

author: CaptDon
author_rank: Super Contributor
timestamp: January 27, 2021, 05:54:28 pm
content: I have always just soldered my leads into the connectors. They were crap from day one and many companies used them.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: January 27, 2021, 05:58:21 pm
content: Thank you for your reply.I have thought about soldering the wires to the plug but there is not much room for the soldering iron tip.Is there a special procedure you used to get the wire, solder and the iron tip in that small opening to solder?

author: coromonadalix
author_rank: Super Contributor
timestamp: January 28, 2021, 01:34:26 am
content: hum not sure they look like mta 100 connectorshttps://www.te.com/usa-en/products/connectors/pcb-connectors/intersection/mta-100-mta-156-connectors.html?tab=pgp-storyjust need to be sure of the pitch, i use tons of them at my job, the amp tool to crimp the wire cost a fortune +/- 200$If you do some repairs, skin/remove 3-4mm of the wire and try with an small eyeglass flat screwdriver to push the skinned wire into the plug and use 60/40 63-37 solder, you may add some flux BUT be fast, it may melt the plug or the solder may get sucked further down the plug, filling the pin hole ....you need to get a relatively fine pitch solder tip ??good luckIf the pitch is 0,1 you could try to find 1 row connectors like this ?https://www.ebay.com/itm/50pcs-Pitch-1x-9-Pin-2-54mm-Female-Single-Row-Straight-PCB-Header-Strip-Socket/291558160354?
Help with smd components - Page 1
Forum section: electronics / repair

author: error21
author_rank: Newbie
timestamp: July 11, 2019, 03:05:40 pm
content: Hicould anyone please help me identify these 2 smd components? (the zd2 and zd6 both have W98 as some marking on the side so I guess they are the same, but I cannot find what kind of zener diodes they are)all the components are on a PSU on the live side.Update: maybe the diode is this one:https://www.rohm.co.kr/datasheet/TFZ24B/tfzgtr24b-e( TFZ24B )Thanks

author: fzabkar
author_rank: Super Contributor
timestamp: July 12, 2019, 01:19:50 am
content: Could this be the transistor?http://www.gmicroelec.com/KUpload/product/TR/PXT8050%20SOT-89.pdfhttp://jcet.svell.cn/gallery/txUpfile/30465bc5ca1ca5713ff57725ac02ff7e.pdf

author: error21
author_rank: Newbie
timestamp: July 12, 2019, 07:56:42 am
content: Thanks
Help with SMD IC Identification - Page 1
Forum section: electronics / repair

author: vegaspeaker
author_rank: Newbie
timestamp: September 07, 2024, 03:56:41 pm
content: First-time poster here. I'm an electronics repair hobbyist. I've never had any formal training. I took up electronics in college and enjoy the field.The current project on my bench is a 15" flat screen TV (Venturer PLV76156) with a failed power supply. The obvious problem was the failed main filter cap. Unfortunately, it took out several other things with it. Some SMD resistors were damaged which I already replaced. The main MOSFET was shorted and replaced. I now get 170VDC on the main cap and all the way to the MOSFET and input of the transformer. That's all I get. 170VDC through the transformer. It's not switching on and off.The culprit appears to be the IC for the gate. I'm getting strange, very low, resistance readings on at least a couple pins.I've tried my best researching for the actual part number of this 6 pin (SOT457?) device. It's big enough to have a logo on it, but I haven't been able to match that to any company. As extensive as this list (https://componentstash.com/reference/semiconductor-logos) is, I didn't see it on there. I haven't been able to match any of the markings to anything that makes sense. That's why I'm here. This TV isn't worth much, but if I didn't think I could fix it I wouldn't have started. Right now this one device seems to be hanging me up.BTW, the second picture is more representative of what you see in person.Any help would be greatly appreciated.Greg
Help with Starlink Dish repair - Page 1
Forum section: electronics / repair

author: redor
author_rank: Newbie
timestamp: April 09, 2025, 07:30:52 pm
content: Hello everyone,I‘m in a bit of a pitty. I have a Starlink Gen 2 Dish and it is not doing anything. The Main Coil was detached due to a drop and I‘ve repaired that. I have measured all voltages with a multimeter and the are fine, but the SoC stays cold and the voltages for the Sat-Part aren‘t turned on by the SoC. The SoC stays cold and the only thing getting remotely warm (~27C) is one side of the emmc.What should I do now? I‘m suspecting a broken solderjoint/pad underneath one of the BGAs (emmc, SoC or RAM)Is there something which I can check besides that?Is the emmc the right Point to start or should the SoC get warm regardless of the emmc/ram if it is fine?Is a reflow sufficient or is there zero chance of a broken solder ball vs. A ripped pad underneath?(The damage is most likely due to board bend/flex during removal/drop)

author: thm_w
author_rank: Super Contributor
timestamp: April 11, 2025, 12:16:26 am
content: SOC would be warm regardless of emmc state. But there may be some lower level power management.Is it similar to this:

author: DaJMasta
author_rank: Super Contributor
timestamp: April 11, 2025, 12:21:59 am
content: Are you sure you've checked all the external voltages for the SoC? Otherwise inspecting for broken traces around it and then going for the reflow would be my approach.
Help with Tektronix TLA7E2 Power-On Kernel Fail - Page 1
Forum section: electronics / repair

author: softnado
author_rank: Newbie
timestamp: November 22, 2021, 09:08:49 pm
content: New to forum, feel free to point out post problems.I recently received one TLA7E2 for my TLA721. All other tests passed except the Power-On Kernel. Did some research on EEVblog, old posts seems indicate something to do with battery powered chip with system configurations. Want check with experts before I pear off that calibration seal sticker. Thanks and regards.

author: softnado
author_rank: Newbie
timestamp: November 23, 2021, 01:36:45 am
content: Attach pictures of processor board and the chip with battery. Will the battery issue cause Power-On Kernel fail but NVSRAM test still pass?

author: softnado
author_rank: Newbie
timestamp: November 23, 2021, 06:35:54 am
content: How stupid I am. Turns out that the board is working, the only thing it needs is reflash the newer firmware that come with TLA721. The special part is old TLA7E2 require firmware flash jumper pin connected. After that, everything works.
Help with unknown smd IC - Page 1
Forum section: electronics / repair

author: error21
author_rank: Newbie
timestamp: July 28, 2019, 04:36:01 pm
content: HiCould somebody please help me with the following IC? They are from 2 different products and I THINK they are used to measure the input current.I did look on google but could not find anythingWhat I did measure is that PIN2 is GND and PIN5 is +5V and between 3 and 4 there is a 100K resistorThanks

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 28, 2019, 04:47:27 pm
content: Looks like this:http://pdf1.alldatasheet.com/datasheet-pdf/view/658183/SGMICRO/SGM8271.html

author: fzabkar
author_rank: Super Contributor
timestamp: July 29, 2019, 05:17:18 am
content: http://www.smdmark.com/en-US/search/code?id=sg5https://www.bing.com/search?q=sgm8271+filetype:pdf
Help w/rectifier ID? - Page 1
Forum section: electronics / repair

author: cvanc
author_rank: Frequent Contributor
timestamp: December 23, 2019, 05:45:44 pm
content: My Google-fu seems weak on this one, I'm not finding anything on this rectifier. Anyone got an idea what this is and where a datasheet can be found? Thanks, as usual...

author: WyverntekGameRepairs
author_rank: Regular Contributor
timestamp: December 23, 2019, 06:01:28 pm
content: Edit: Confirmed. It is a high-voltage, general purpouse rectifier diode in a transistor-like (TO-220-2L) package. The series is called "Stealth" by the looks of the Digikey description.Remember that a lot of manufacturers only include part of a part number on small packages that can't hold the entire number. This is one of those cases. The full part number is ISL9R8120P2, but on the package they cut a portion of the part number off.Here is the Digikey page for it, you can find a datasheet for this diode there:https://www.digikey.com/product-detail/en/on-semiconductor/ISL9R8120P2/ISL9R8120P2-ND/565978?utm_campaign=buynow&utm_medium=aggregator&WT.z_cid=ref_findchips_standard&utm_source=findchipsHope this helps
Help in identifying SMD part. - Page 1
Forum section: electronics / repair

author: suntime
author_rank: Contributor
timestamp: March 08, 2025, 04:38:59 pm
content: Hi,I'm trying to fix the power supply of an amplified speaker, but I can't identify an SMD component with the inscription 'W215J' and with some help and luck maybe I can get it here.I have enclosed part of the SMPS electrical circuit and an image of the component that appears to be the one I drew in KiCad.Thanks.

author: squadchannel
author_rank: Frequent Contributor
timestamp: March 08, 2025, 04:49:23 pm
content: missing picture

author: suntime
author_rank: Contributor
timestamp: March 08, 2025, 09:05:37 pm
content: Sorry for the missing images

author: Whales
author_rank: Super Contributor
timestamp: March 08, 2025, 09:54:41 pm
content: Between a micro and a gatedriver is a weird spot. TVS would not make sense unless the tracks are long and user accessible (parts on different boards?).Maybe it's an NPN transistor that shorts one of the signal lines down whilst the other is high, as a shootthrough prevention method? Odd but maybe an extra layer of protection beyond the micro firmware. I don't think that gatedriver chip has any in-built lockout between the upper & lower driver.Do you have one of the cheap transistor tester boards? You can hold SOT23's against their test pads (with a little bit of difficulty) and find out more.

author: suntime
author_rank: Contributor
timestamp: March 08, 2025, 10:10:43 pm
content: What I know is that with the positive end of the multimeter on pin 3 and the other end on pin 1 or 2, it measures like a normal diode (0.6V) and if I measure with the Peak Electronics Atlas ZEN50 I get 7.8V and 7.1V with the black end on pin 3 and the red end on pin 1 and 2.The values ​​mentioned are from a component that appears to be good, because the one that is damaged has one of the diodes shorted and the IC U8 blown.On the printed circuit board it is marked as DZ3.

author: fzabkar
author_rank: Super Contributor
timestamp: March 08, 2025, 11:51:09 pm
content: The equivalent circuit for U8 shows internal ESD diodes on its inputs and outputs. "DZ3" would suggest a Zener or some kind of clamping diode.https://www.infineon.com/dgdl/Infineon-IRS21867S-DataSheet-v01_01-EN.pdf?fileId=5546d46269e1c019016a4e24fc670c35Are there any Year/Week date codes on the other ICs which could help us to discern the date code digits on DZ3?

author: inse
author_rank: Super Contributor
timestamp: March 09, 2025, 03:14:50 am
content: An interlocking add-on seems to make little sense as half bridge gate drivers with internal (certified) logic are available.I assume its a protection circuit to provide immunity against ground shifts between the logic and the load side.

author: suntime
author_rank: Contributor
timestamp: March 09, 2025, 12:59:05 pm
content: Hi,I think this is it:https://www.we-online.com/components/products/datasheet/824021.pdf

author: inse
author_rank: Super Contributor
timestamp: March 09, 2025, 04:21:24 pm
content: Well spotted!
Hewlett-Packard 1741A Calibration Frequency Drift - Page 1
Forum section: electronics / repair

author: El_Berto
author_rank: Newbie
timestamp: December 01, 2023, 11:05:32 pm
content: Greetings, first post.....I have a 1741A and a couple frequency counters. Just futzing around while reading the manuals I decide to plug the 1741A calibration posts to the counter. The documented frequency of the 1741A calibration posts is 1400 Hz. The counters tell me another story, both agreeing to something like 1611.x Hz. Each counter using their internal clocks, as opposed to a shared external time base. On their internal tests, the counters are spot-on.There is a volt peak-to-peak adjustment in the 1741A but not a frequency adjustment, even then a +-14% offset just does not make sense. With a slow DMM the output is measured at 0.495v, which seems sort of normal since the signal is a 50% duty cycle square wave. I am thinking that there is something going on inside the scope, i.e. some component(s) on it's way out.Has anyone seen this in a 174x or similar scope? Is this frequency used internally for measurement results and if so what? Any suggestions would be welcome.Thanks Dave. Cheers, Bert

author: factory
author_rank: Super Contributor
timestamp: December 02, 2023, 10:39:11 am
content: Did you see my reply on the HPAK group, instructions state the frequency is "approx" 1400Hz. It's used externally for checking/setting the probe compensation.The calibrator circuit is on the A3 board, I would look at R100 (301k) & C47 (910pF), it's possible the Mica cap has lost a little value, due to silver migration problems that Mica caps are known for, or the resistor has gone high in value.The output of U4B is used for other things in the scope, this is common with the analog storage scopes from HP.David
Hewlett-Packard 3302A Trigger/Phase Lock Plug-in for 3300A - Page 1
Forum section: electronics / repair

author: oz2cpu
author_rank: Frequent Contributor
timestamp: September 17, 2022, 12:16:19 pm
content: IT IS DRIVING ME NUTS..no one ever shared a schematic for this module online ?the phaselock part of it is not working,previous owner messed a round in it, many funny solderings, and dots from scope probesreveal he spend a long time trying to figure this out..anyone got a schematic ?

author: wn1fju
author_rank: Frequent Contributor
timestamp: September 17, 2022, 04:07:59 pm
content: Try:https://xdevs.com/doc/HP/3302A.pdf

author: oz2cpu
author_rank: Frequent Contributor
timestamp: September 17, 2022, 09:40:05 pm
content: thanks mate, funny how many contacted me to tell me this :-)and even more funny it did now show up on any of the many searches i performed
Hewlett Packard 3336B replacement control board - Page 1
Forum section: electronics / repair

author: Wazza
author_rank: Contributor
timestamp: December 30, 2024, 11:26:01 pm
content: Hi all,I'm attempting to repair a hp3336b and have found it has a replacement control board (03325-66516) fitted.This is not documented in any of the service manuals I can find, but is referred to in 'service note 3325-A21' or the service manual change sheets for the 3325 generator (the 3325 generator can also use this replacement control board).Does anyone have information on this newer control board?Regards,Waz

author: m k
author_rank: Super Contributor
timestamp: January 04, 2025, 09:32:19 pm
content: 90003 manual has 526 board.Maybe you can gain something by comparing previous and next.At least you can say what are still like they used to be.
Hewlett-Packard 723A power supply refurbish - need schematic - Page 1
Forum section: electronics / repair

author: Arty30
author_rank: Regular Contributor
timestamp: September 10, 2022, 06:08:46 pm
content: I just picked up an HP 723A power supply that I want to clean up. It appears to work but could do with a look-over seeing that its from the first half of the 1960s. Here's an HP journal from Feb, 1961 describing it:https://worldradiohistory.com/Archive-Company-Publications/HP-Journal/60s/HPJ-1961-02.pdf. I can't make out any of the details on the capacitors and was wondering if anyone has a schematic/parts list or knows where to find one, Thanks.

author: bdunham7
author_rank: Super Contributor
timestamp: September 10, 2022, 06:12:30 pm
content: Artek has the manual for $10, I don't see any free ones online.
Hewlett Packard '60's gray and '70's beige touch-up paint - Page 1
Forum section: electronics / repair

author: Tomorokoshi
author_rank: Super Contributor
timestamp: May 19, 2017, 04:31:43 pm
content: I am looking around for touch-up paint for Hewlett Packard equipment. I am interested in the '60's gray color, and the early '70's beige.I looked at the Keysight parts web site but nothing is listed.Looking over 5 very difference pieces, some certainly from different factories, shows remarkable matching overall for beige anyway. If there is a difference it's more in density instead of an actual color shift.The scratches don't matter so much; it's where they tore off the old calibration labels that I want to repair, so it's an area of perhaps 1 square inch.Eventually I might try to mix Testors model paint, but I would never get the sheen right.Another option: I could take the equipment into a paint store and see if they can mix up something that would match.

author: Cerebus
author_rank: Super Contributor
timestamp: May 19, 2017, 05:01:42 pm
content: Myguess, and I must stress it is a guess, is that the HP colours are probably colours from a standard industrial paint colour scale such as RAL, BS4800 and FED-STD-595.

author: james_s
author_rank: Super Contributor
timestamp: May 19, 2017, 06:51:19 pm
content: If you can't find a suitable match, you might take it to an automotive paint supplier and have them mix you some. Often they can even put it in an aerosol spray can for you if you don't have a spray gun.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 19, 2017, 08:34:20 pm
content: If you can take a piece in, alot of places that sell paint such as a hardware store or auto-body shop will have a colorimeter that can match the paint to what they have in their computer database.

author: jemp
author_rank: Contributor
timestamp: July 08, 2023, 08:52:01 am
content: Hi, I came across the same question , some time agoIf any help for the moment or the futureThe Colour RAL7032 will do nicely, practically the sameSuc6Jemp

author: Cecil
author_rank: Contributor
timestamp: July 08, 2023, 08:55:00 pm
content: I second the recomendation to go to a paint store. They can scan a sample and a computer will generate a list of pigment colors and quantities that will turn base white into any color. They can similarly control the scheen between flat and glossy. Cost could be a problem though because you'll probably have to buy a gallon of paint. Most body shops also have a human who is expert at matching paint but I suspect most won't offer the service unless you hire them to fix your car.If you want to spray touch-up quantities, look for a Preval sprayer at the paint store, Amazon or a big box home imprpovement retailer. It includes a 9oz. bottle and a small can of pressurized gas that will allow you to spray small quantities of any paint. If you have compressed air, then a tiny and cheap paint sprayer from the likes of Harbor Freight can give bettery economy.
Hewlett Packard HP70908A 22GHz RF section ROM checksum error - Page 1
Forum section: electronics / repair

author: Lightbox Solar
author_rank: Newbie
timestamp: August 18, 2021, 04:29:59 am
content: Hi,My HP70908A RF section has developed error 7009: ROM #2 checksum error. Just wondering if anyone has an image / is willing to make one?The chip is A12U7, a Xicor X2864AD 8k x 8 EEPROM. HP programmed part no is 70908-80001The unit still boots and seems to run fine

author: KE5FX
author_rank: Super Contributor
timestamp: August 18, 2021, 07:01:45 am
content: If the ROM images aren't already available on ko4bb.com, I'd recommend posting your inquiry to the HP-Agilent-Keysight-equipment group on groups.io. There are quite a few HP 70000 owners who hang out there.

author: Lightbox Solar
author_rank: Newbie
timestamp: August 18, 2021, 11:05:04 am
content: Hey KE5FX, it's been a while - I think you helped me out 10+ years ago on the Yahoo Groups HP repair page to fix an issue with the 70908A's discriminator loop when I first got it!Had no idea those guys moved to another platform - will check it out.Cheers!
Hewlett Packard HP8922M and HP3325B SRAM Battery replacement - Page 1
Forum section: electronics / repair

author: BLReklov
author_rank: Newbie
timestamp: December 17, 2021, 08:09:14 pm
content: Hi,I recently acquired a HP8922M GSM Test Set and an HP3325B Synthesizer/Sweeper. Now I would like to back up the ROM´s and change the SRAM Batteries for good measure. Im new to electronics repair stuff. What should I look out for and can I just replace the Batteries with the units powered on or should I hook up a Power Supply to the SRAM?Thanks in advance.

author: alm
author_rank: Super Contributor
timestamp: December 17, 2021, 10:41:09 pm
content: Check if the battery-backed SRAM contain settings that are hard to recover, like calibration, or just convenience settings like the last front panel state. If the former, there are two ways (that can also be combined).Replace the battery while the instrument is powered on. Be very careful not to short anything. If it's a solder-in battery, make sure your soldering iron tip is not grounded. A trick I've used in the past is to unplug the iron just before touching the solder joint, so it's disconnected from power (and ground) while you're touching the board.Power it from a floating source, like soldering a temporary battery with series diode in parallel.You can also go belt and suspenders by using both external power and a temporary parallel battery. Especially if you're worried about your mains power failing at just the wrong moment. There are some tips inthis thread on replacing the HP 3468A battery..If it's a simple battery holder, then the same applies, but you don't need to do any soldering. Power it on, optionally connect another battery in parallel, and replace the battery using non-conductive tools (if any).
HGST/WDC Ultrastar He12/HC520 - Page 1
Forum section: electronics / repair

author: JoeRoy
author_rank: Regular Contributor
timestamp: March 18, 2024, 05:16:39 pm
content: This is a HGST/WDC Ultrastar He12/HC520.The HDD is spinning, but not be recognized, I guess this is the culprit, I think is an SMD inductor.I'm looking for the schematics to find the value. Maybe I can remove it and put a 0hmns bridge?Any help is appreciated. Thanks.

author: fzabkar
author_rank: Super Contributor
timestamp: March 18, 2024, 05:55:12 pm
content: That appears to be a normal moulding mark. I believe that this area is the -3V supply for the preamp (on the headstack). This supply may not be enabled if the board is tested off the drive.This tutorial should explain how this voltage is generated:https://www.hddoracle.com/viewtopic.php?p=596#p596See the attachments for the other voltage test points.Other references:https://www.hddoracle.com/viewtopic.php?p=22339#p22339https://www.hddoracle.com/viewtopic.php?p=22340#p22340That said, if the drive spins up, then the PCB is almost always OK. Instead the fault is due to the drive's inability to reach the reserved firmware area on the platters (System Area, SA, discware). That is, the fault is most likely related to bad heads.The hard drive -- a computer-within-a-computer:http://www.hddoracle.com/viewtopic.php?p=19087#p19087

author: JoeRoy
author_rank: Regular Contributor
timestamp: March 18, 2024, 06:06:32 pm
content: Thank you. yes, I found other pictures and they have this mark, when I saw that, I thought was burned.I'll investigate. Thank you for all the details.
Hi newbie here!! Thanks for the add!! Question for anyone. - Page 1
Forum section: electronics / repair

author: metricscaleer
author_rank: Newbie
timestamp: April 22, 2024, 04:18:08 am
content: I was working on my camper van which has solar panels, a solar controller { 20 Amp MTTP } two 100AH deep cycle batteries, and an inverter. the solar panel and the battery in connections in the controller were really loos so I disassembled it and resoldered the pins that went through the circuit board and it looks I was successful, my question is when it tests for continuity on the battery + - I have it but i don't have it when I test the solar panel in + _ I was wondering if I should have continuity but i don't knowThanks!!!

author: Shock
author_rank: Super Contributor
timestamp: April 22, 2024, 11:49:16 am
content: Multimeter continuity/resistance/diode/capacitor functions are all fornon poweredcircuits. Multimeters on these tests a apply it's own voltage/current to the circuit under test (so therefore polarity matters). If you think you may have a semiconductor/diode blocking current in your test you can try the diode function and or reversing your test leads to get the polarity correct.So the inverter needs to be switched off and the power sources (solar panel/battery) fully disconnected/isolated. You can test one wire at a time if it's isolated at one end but you must be sure it has no current running down it.It's best to test powered devices or voltage sources (in this case) with the dc voltage function across both conductors and dc voltage drop measurements down individual conductors. This is the "live" way to determine if there is a high resistance (bad) connection.
Hickok 1605M voltmeter  - Page 1
Forum section: electronics / repair

author: TimFox
author_rank: Super Contributor
timestamp: July 14, 2019, 09:40:04 pm
content: While I wait for the manual that I ordered on eBay, can anyone tell me the function of each of the six calibration pots facing up on the top board? I have the version using an AD 545 op amp, not the older version with photo chopper.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 15, 2019, 01:19:39 am
content: I would say take their values before adjusting them, and maybe by trial and errors you could find their use ??

author: TimFox
author_rank: Super Contributor
timestamp: July 23, 2019, 08:59:52 pm
content: I now have the manual. In case someone finds this on search, here is the layout of the calibration pots on the top board, seen from above. Each sets the full-scale value. Hickok recommends adjusting at 80% of F.S., and using 400 Hz for AC voltage calibration.REARR48 [50 mA DC]R47[0.05 V DC]R37[0.5 V AC]R39[1.5 V AC]R41[5 V AC]R44[50 V AC]FRONT
Hickok 539B / 539C Repair question (uMHO meter test)  - Page 1
Forum section: electronics / repair

author: WimWalther
author_rank: Regular Contributor
timestamp: April 29, 2023, 02:49:52 am
content: Howdy,I have here a Hickok 539B tester, it's the late model with round AC line & bias meters. I cannot get any indication on the main (uMHO) meter with any switch settings I've tried. It would seem prudent to first eliminate the meter (coil) itself as the issue.How can I make a direct resistance test of the meter movement without disassembling the tester and pulling the meter out? It's kind of a pain** on these models and I'd like to avoid it.Is there some switch setting that directly exposes the meter winding to some point(s) on the front panel, for easy testing? Some other simple, semi/direct method?TIA, Bill(** I'm not just lazy, but physically disabled.. I can't even put the unit on the bench without help, much less manipulate it as needed for disassembly. They seem to become heavier with each passing year.)

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: May 01, 2023, 12:02:36 am
content: Hello Bill,The 539B/C's meter is an odd 115uA, 1,500 ohm, 172.5mV (full scale) meter. I haven't checked the schematic but I don't recall any direct external connections to the meter. I wouldn't use an analog meter to measure the meter as most put a fair amount of current out and you don't want to overload the meter too much. A DVM should work just fine as they use lower currents. These units are a bit of a hand full to get into and support while digging around in them. Hickok used meter movements from 50uA up to 1.4mA, few of them being standard meter values but a different lower current movement can be substituted fairly easily if necessary.There is a 100uF capacitor (C4) across the meter's terminals, odds are this capacitor is leaky and since the meter is a 115uA movement, it wouldn't take that much leakage to mess things up. I doubt that the meter movement is bad.Regards,Edwin

author: WimWalther
author_rank: Regular Contributor
timestamp: May 27, 2023, 08:27:54 am
content: Howdy All,I've been majorly sidetracked with health issues (dialysis troubles mostly) and haven't so far been able to get back to my friend's 539B. So I felt like I should quickly check-in, reaffirm that your assistance isn't for naught, and see if there were any new replies.I'll try to get back with something of substance sooner rather than later. Thanks again for your time & input.. much appreciated.
Hickok 539B - Help with wiring bias potentiometer - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: June 04, 2025, 09:38:54 pm
content: I had to take out the bias pot to repair it. I marked all the wires but somehow I ended up not knowing where the white with brown stripe wire gets connected.I tried following the schematic but the wires on the back of the 10v and 50v switch are different on my schematic.Could someone tell me what wires get connected to the terminals on the pot? Also what looked like a black stripe to me was actually purple.Thank you in advance.Chuck

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: June 05, 2025, 07:41:44 am
content: Use a multimeter to identify where each wire goes (grid resistors, ground, bias supply). Match this with the schematic voltages and positions, not just colors.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: June 05, 2025, 09:49:04 pm
content: I found a schematic that is close to my wiring. I've attached a copy.I traced each wire to make sure I had the correct wire to attach to the bias potentiometer.Now the 10 volt range only goes up to about 5 volts and on the 50 volt range I get 0 volts no matter where I set the bias potentiometer.what could cause this? Do I have the wrong schematic or did I mess up.
Hickok 539B help - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: March 13, 2025, 08:05:42 pm
content: Has anyone had the same problem I have with my Hickok 539B?On Diode tubes the meter goes off scale.With other tubes including 6L6 the meter does not indicate anything.The meter is good. I cleaned all the switches and controls, replaced all capacitors. The tester was purchased as-is.Thank you for your help.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: March 14, 2025, 11:47:07 pm
content: Just an update.I'm going through the calibration.With my variac set to 110 volts and the voltage on the Hickok set to 100 volts (red test) and all the settings set as listed in the calibration manual, I'm getting 187 volts on the plate instead of 150 volts when I press P4. With the plate volts switch set to low, I'm reading 83 volts instead of 65 volts with P4 pressed..On the screen voltage test, I get 233 volts instead of 130 volts when I press P4. The reading should drop to 56 volts when I Hold P4 and press P1 but the reading stays at 233 volts.Any suggestions what could be wrong? I am using the solid state replacements for the 83 and 5Y3 vacuum tubes.Thank you for any help you can offer.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: March 15, 2025, 01:21:21 am
content: I found the problem. The calibration manual I was using is showing voltages taken with a 1000 ohms per volt meter. Later calibration papers suggest using a 270kohm resistor across the meter probes to "load" the circuit under test.I will try this and see if the gives me a closer reading.
"HiFi" CD radio clock: Z-778PM3Ui - Page 1
Forum section: electronics / repair

author: najrao
author_rank: Regular Contributor
timestamp: December 30, 2020, 12:30:08 pm
content: This rather good looking product was made by "SEM industries, Hong Kong". Not even a user manual is forthcoming, even after an imploring mail.As received, it is dead: needed replacing a zener and two bipolars to get up all of the several power rails. Not to mention a few resistors, capacitors and links which were victims of "snot" corrosion.I have pictured only the display and buttons board. Because exactly these do not show any signs of life. The mother board and the radio board are separate.The display is driven by a Samsung S3P8245 chip. The data sheet and app note shows the LCD pins directly connected to the chip pins; except nos. 48,49 and 50 which are to connect to external caps for voltage doubling or tripling, as the LCD supply. In this unit, 48-50 are led out to the main board thru 1k resistors, and cannot play a part of the LCD supply.More importantly,noneof the LCD pins are left out, all are connected up to pins 51- 80, and to nothing else. So, I do not know what this LCD supply means or where it applies. Yes, I am ignorant and unfamiliar.Each of the LCD pins has a stepped waveform on it, average 1.3V dc. All the same.I have checked that the S3P8245 is active, both the 8.0MHz and 32.768kHz oscillators are working (I replaced the 8M crystal).Neither the display nor any of the buttons show any signs of life.Repairing this some how will bring cheer to an aging relative, who needs such badly.I hesitated a lot before asking help from my eev friends. Kindly help.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 30, 2020, 01:04:30 pm
content: 3 things maybe worth checking- the darkened pcb just above the display driver, it looks like something got hot under the LCD- some liquid spots just above the center of the pcb?- something that looks like there was a short just above and left of where the 2 wires exit at the right bottom

author: najrao
author_rank: Regular Contributor
timestamp: December 30, 2020, 01:42:24 pm
content: Thanks, PAOPBZ.Yes, that was where a transistor had cooked and shorted. I have replaced it. Also, cleaned out the area with IPA. The brown patch is not conductive.The 'liquid' marks are actually just the projecting edges of a small daughter board, which only carries two LED's for display illumination (which works).Bottom corner are just two wires leading to a momentary push button to turn on/off some of the dc supplies; it works too. I have not cleaned properly after reattaching the wires (had broken off).
hifiengine.com - Page 1
Forum section: electronics / repair

author: markav2
author_rank: Contributor
timestamp: January 08, 2023, 10:35:37 am
content: Looks like the webmaster over at hifiengine.com was and is having problems with bots he has purged some of the accounts and it looks like mine was purged. I think he probably purged my account because of my email address which is a custom domain that I own, but it ends in.US. He has closed registration for new accounts and I need the service manual/parts list forYamaha R-N803. I have searched around and cannot find it anywhere else. If you know of somewhere I can find it or if you could use your account to download it from hifiengine.com I would appreciate it.Mark

author: markav2
author_rank: Contributor
timestamp: January 08, 2023, 11:16:09 am
content: This is a link to the files that I am unable to download.https://www.hifiengine.com/manual_library/yamaha/r-n803.shtml

author: Chris56000
author_rank: Frequent Contributor
timestamp: January 08, 2023, 01:57:24 pm
content: Any help?https://www.dropbox.com/s/9ylzriqw9hyc6hf/hfe_yamaha_r-n803_n803d_schematics.pdf?dl=0https://www.dropbox.com/s/gnoped4yx1uykkq/hfe_yamaha_r-n803_n803d_parts_list_en.pdf?dl=0https://www.dropbox.com/s/0zqm21j5i2emvb4/hfe_yamaha_r-n803_803d_en_fr_es.pdf?dl=0Chris Williams

author: floobydust
author_rank: Super Contributor
timestamp: January 08, 2023, 04:57:54 pm
content: I can't download anything from hifiengine.com for a long time now. Something broken with the website."Referer Error: unable to complete your request due to missing or incomplete referer data forwarded by your browser"FAQ: Why do I get a referrer error when I try to download a manual?"If you get a referrer error this means that your browser is blocking referrer information ie not passing on the URL of the page with the download link. Please refer to the documentation of your browser, anti-virus program or firewall for a solution.You can check to see if referrer information is missing on this page."<<<goes to that link>>>"Referrer CheckWhat is referrer information?When a page requests referrer information from your browser it is asking for the address of the page from which the link originatedWhy is this information needed?The referrer is used to check the source of the download request and helps prevent 'hot linking' and 'bandwidth theft'.Is my browser blocking referrer information? NO"Referrering page =https://www.hifiengine.com/referrer-check.phpFAQ: How do I contact the webmaster?"This website is provided as is. If you have a query about using the website please read the FAQ above for answers to frequently asked questionsNote that it is not possible to provide support for registration/login/download problems beyond what is written hereIf you have been banned for registering multiple accounts, this is permanent."In my browser I have "Send the HTTP referrer header on all requests", adblocking turned off etc.I just gave up, I could not find the problem.