hybridfree/eevblog-posts huggingface dataset:
HP/Agilent 3634A Repair - Page 1
Forum section: electronics / repair

author: sahko123
author_rank: Frequent Contributor
timestamp: April 26, 2021, 10:36:14 pm
content: This thread is basically for anyone who has the issues listed below and what I did to repair them.1. Non-sensical/maxed out reading beyond range.2. Collapsing voltage at any current1. One of my 3634As when powered read beyond maximum voltages at around 54V and 7A. Part of the manual tells you to test the bias voltages. In mine the +15 rail read 0.8V which was traced to a broken CR9 2.4V zener diode. I repaired it with a through hole zener diode with the same voltage but higher power dissipation. This was because I couldn't be arsed waiting for the actual part to arrive and it made no difference. But anyways fixing this diode made the power supply work fine with no strange readings. I think the measurements are based of these rails but thankfully the 3634A has a calibration mode that can be accessed a power cycle while holding error for 5 seconds at power up.1. (solution) Replace CR9 2.4V zener2. The second 3634A would output the displayed voltage perfectly and even voltage calibration worked perfectly the problem was that when a current of more then 1 or 2mA was applied the voltage would collapse completely. This problem was slightly stranger to troubleshoot everything on the board measured fine at first I thought that the power regulator was at fault. I decided to test the components directly on the output by feeding 10V into the input and tracking it back. There was a resistor directly across the output which is 4.7K i measured the voltage across the resistor which should have been ten while inputting 10V from another supply. This resistor should have been directly across the output. Then i noticed that the sense wires are connected to the output through a resistor internally, I had them shorted externally on the binding posts. So I continued tracking the output voltage and noticed that there was no 10V anywhere but the actual binding posts. As it turns out the binding posts are not one piece from output to the board they are soldered just on the inside. So measuring the continuity from the binding posts to the board meant that the post itself was at fault. The solder was reflowed and more was added to make sure this fixed the supply. The reason i measured the correct voltage was because the sense and output was shorted to each other with the power output going through the resistor connecting them internally was output to the sense binding posts which was in turn connect to the output through the short. So the collapse was caused by the dicky binding posts2. (solution) Reflow or add solder to the binding posts or specific dysfunctional binding post.
HP/Agilent 4156C failing self test on power on - Page 1
Forum section: electronics / repair

author: chilternview
author_rank: Frequent Contributor
timestamp: August 25, 2023, 06:27:30 am
content: I'm seeing one or more SMUs fail self test at power on. The error code is 10x24 where x is the SMU number, apparently this error is 'SUM failed I set and I measure calibration'The error goes away after the unit has been powered on a while, but I'm concerned it may get worse. Has anyone seen this error message, and found a solution? Unfortunately the service manual does not have any schematics. I'm guessing that if just the current calibration checks fail (and not the voltage ones) it may be something like leakage in the range resistors?

author: chilternview
author_rank: Frequent Contributor
timestamp: September 18, 2023, 07:21:55 pm
content: So this problem with errors 10x24 and also 10x27 is caused by input leakage in current measure mode.I found that carefully cleaning the HRSMU board with a clean soft brush and also a hot air gun set to low temp (100C) to blow away any dust around the OPA128LM and associated components (they are under a screen, under another screen for the analog section of the HRSMU) got rid of the problem. Handle with plastic gloves on to avoid getting any sweat etc on the board. Even the slightest touch in the wrong place can give rise to leakage.
HP/Agilent 6614C schematic - Page 1
Forum section: electronics / repair

author: Octane
author_rank: Regular Contributor
timestamp: November 11, 2023, 05:24:54 pm
content: Hey all,I've scored a damaged Agilent 6614 power supply from the electronics trash at work. It had a sticker saying "Unr" on it and indeed it showed the unregulated annunciator when it was powers on and the output was activated.No voltage appeared at the output terminals. A short investigation showed that the Rail+ line was not there, and with the help of the service manual I found F311 to be blown.Shorting it with the multimeter in current mode showed a current of about 150mA and the supply went back into regulation. At least for the CV mode.The display showed a constant current (which is not running through the output terminals) and when I try to get it into CC mode it does many weird things. Showing negative output voltage, and currents that are not the ones I set.I also found a blown cap (C375 on the A1 board), which I removed, but that did not change anything. Furthermore I tried to make sense of the control signal coming from the A2 interface board, but they are kind of all over the place.Without a schematic I'm kinda stuck.So does anybody have schematics for the HP/Agilent 6614C? That would be really helpful for the troubleshooting. The service manual is too vague for me to make real progress.Thanks,Michael

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: November 11, 2023, 09:20:30 pm
content: Linking in the service manual for clarity.http://ridl.cfd.rit.edu/products/manuals/agilent/power%20supplies/cd1/service/6611Cser.pdf
HP/Agilent E3610A calibration - negative and non-linear meter reading (solved) - Page 1
Forum section: electronics / repair

author: CatNinja
author_rank: Newbie
timestamp: September 25, 2022, 08:27:22 pm
content: My E3610A meter readings were always slightly off (negative at 0v, about 30mV low at 5V), so I tried calibrating it as per the Service Manual.However, there is only 1 adjustment pot for the voltage, which only allows you to adjust it to be accurate at the recommended 15V. After calibration, I still get a negative reading at 0V, but worst of all, an error that is non-linear across the range, ranging from -0.02V at 0V, -0.03V at 3.30V, +0.05V at 9V, to 0V at 15V (calibrated for this voltage). Looking at the forums, it looks like a lot of people have the same issue with negative zero voltage reading, and the recommendation is just to live with it since it's just a built in power supply meter.The display driver is a Microchip TC7107, and it's auto-zeroing, which is why there is no pot for zero adjustment. It's used in a lot of low-end DMMs, so it should be a lot more accurate than what I'm seeing. I don't see any obvious bad components in the display either.I finally found a thread that describes this type of multimeterhttps://www.eevblog.com/forum/testgear/old-fluke-multimeters/875/and it described how sensitive these chips are to board contamination. So I cleaned the display board thoroughly with IPA even though it looked clean already. I didn't want to dismount and soak it, so I just brushed on IPA and wiped it off several times. It's now dead accurate (within 1 digit, measured with a 34401A) across the entire range, and reads +/- 0.00V at zero.I hope this helps someone else with this power supply. It's my favorite by far, especially now that the meter reading is accurate.
HP/Agilent E3631A power supply: calibration question - Page 1
Forum section: electronics / repair

author: chr42
author_rank: Newbie
timestamp: March 21, 2025, 12:09:53 pm
content: Hello everyone,I have a question related to a recently acquired HP/Agilent E3631A power supply.Checking out the unit, I found that the measurement of the actual current for the 6V channel is showing a +22mA offset. The attached picture shows this for open terminals.When the 6V channel is operated in CC mode, the setpoint entered in the limit menu is what is flowing through the load. I have checked this with an HP3478A multimeter.All other indicated values (6V voltage, 25V voltage, 25V current, -25V voltage, -25V current) exhibit excellent setpoint/readback agreement and also comparing in CV and CC mode with my (uncalibrated) HP3478A shows very good agreement.Checking some documentation, I guess this +22mA offset is somewhat out of spec. Since the unit is otherwise in good condition, I am wondering if this +22mA offset in measurement of the 6V load current can be calibrated away? Or is this indicating some malfunction in the unit?Thanks

author: benj38
author_rank: Frequent Contributor
timestamp: March 27, 2025, 02:01:32 pm
content: This is a malfunction.
HP/Agilent E3642A PSU Binding Posts - Page 1
Forum section: electronics / repair

author: JohnPi
author_rank: Regular Contributor
timestamp: December 16, 2021, 01:48:20 am
content: The binding posts on my PSU were broken, and OEM replacements are not easily available. This is the plastic holder for dual 4 mm binding posts. It fits commonly available posts. The design follows the OEM one.This was atrial copy -- the final one is printed in gray" alt="" class="bbc_img" />
HP/Agilent E3645A PSU plastic? - Page 1
Forum section: electronics / repair

author: Stray Electron
author_rank: Super Contributor
timestamp: September 26, 2025, 09:21:28 pm
content: I noticed this morning that I must have bumped my HP E3645A power supply and I knocked a chip out of the plastic trim around the front edge. I found the chip and it's intact. Does anyone know what kind of plastic they use and what's the best glue to glue the chip back in with? Mine is the desk top model with the plastic trim and not the portable model with the thick rubbery trim. It looks like thishttps://www.ebay.com/itm/386270622338

author: Kwakerman
author_rank: Regular Contributor
timestamp: September 26, 2025, 09:49:40 pm
content: I tried loctite superglue on my cracked 3631A facia and it seemed to work ok. That said, I wasn't happy with the overall strength / look after the repair (multiple fractures and loose bits) so I ended up getting a replacement from China which was fine. Assuming your 3645 is the same form factor / size as a 34401A or 53131A then you would be able to fit a bumper set to it if that would make the repair look better.
HRU-WALL-150 dead mysterious fan motor - Page 1
Forum section: electronics / repair

author: 4cx10000
author_rank: Regular Contributor
timestamp: November 15, 2024, 03:42:26 pm
content: Hi all!Suddenly a HRU-WALL-150 landed on my bench with non working fans. This is (text directly taken from the owners manual) a single alternate flow decentralized (single point) residential heat recovery unit, also called «push&pull» unit. Link to the manual:https://www.vvs-eksperten.dk/amfile/file/download/file/354/product/10161/The customer told me that both fans worked before they did some changes with the wiring. The manual states that it is extremely important to connect neutral and phase correctly, otherwise it will lead to malfunction or permanent damage of the fan – which words can be seen on a label in a quick made attached schematic I did over the PWM driver circuit for the fan. However, their changes of course ended up wrong – phase on neutral and vise verse.Why would incorrect connection of neutral and phase cause damage to the fan? I did not find a data sheet that has information enough for me to understand why. I may open it and have a look at the small pcb at backside of the the motor. Here is a link to a more-to-wish data sheet what to me looks closest to the fan I have on the bench:https://www.everelgroup.com/wp-content/uploads/2023/03/EC-BRUSHLESS-MOTOR.pdfSo ... what do you guys think?
Help with HSTNS-PD11 (pn:438202-002) DPS1200FB  - Page 1
Forum section: electronics / repair

author: tirman
author_rank: Newbie
timestamp: February 09, 2022, 04:46:49 pm
content: I'm trying to repair a PSU HSTNS-PD11 (pn:438202-002). This power has all outputs 4,8V and 12V STBY ok.... but ...there isn't 12V output! I pulled out a control board (+12VFB), but I couldn't find any failure. Do you know where is 12V ouput control? Could you help me? I've checked all mosfet and capacitor....I'll upload some photos. I promise.

author: tirman
author_rank: Newbie
timestamp: February 09, 2022, 06:21:42 pm
content: Pin 27= 4,8VI connected a ATX64P6 board to turn on the PSU, then these are the values:Pin 28=4,84VPin 29=4,84VPin 30=0,1mVPin 31=4,8VPin 32=4,8VX Pin 33= 0,63V (and 2,9V when it's only plugged to AC and PSON no activated)Pin 34=6mvX Pin 36=0,63VPin 37 (STBY)=12VPin 38 = ---X Pin 64 (12V)= 0VThe PSU turns on and shows 12V, but few seconds later it drops off.I've atttached a pinout that I think it's similar to my PSU and some photos of the board "12VFB".

author: eblc1388
author_rank: Frequent Contributor
timestamp: February 10, 2022, 06:05:40 am
content: Quote from: tirman on February 09, 2022, 06:21:42 pmThere is a very high probability that the ATX64P6 is not compatible with the PD11, unless it works with other PD11 before. You should manually test the PSU before removing the 12VFB board. Here are the steps:1. connects a 18K ~ 22K resistor from Pin36 to Pin37(12V SB). This will make the PSU believe that it is inserted into a power slot of the server.2. jumper Pin33 to GND to start the PSU. If main 12V output becomes available, then you can be sure that the ATX64P6 board is at fault.Quote from: tirman on February 09, 2022, 06:21:42 pmIf main output did produce 12V, then the protection of the power supply likely to be triggered and shutdown the supply. It would not be possible to easily know why this happens. These type of power supply has a ton of monitoring on various parameters(like undervoltage, overvoltage, overcurrent, ....) both via hardware comparator and ADC pins of MCU, making it virtually impossible to troubleshoot unless one has got the full schematic of the power supply.

author: tirman
author_rank: Newbie
timestamp: February 10, 2022, 02:46:18 pm
content: Great eblc1388! Thanks for your help!I´ll try with your advice.

author: tirman
author_rank: Newbie
timestamp: February 10, 2022, 05:57:44 pm
content: Quote from: eblc1388 on February 10, 2022, 06:05:40 amI followed your steps. The output 12V is... in fact... 0V, but the cooler turns on.I understand that we need the schematic, but...Now we know that the fault is on 12V output Perhaps an illumnated soul will give hope and light over this PSU in the next weeks, months...years....
HSTNS-PD18 (aka Delta 750) OVP Hack - Page 1
Forum section: electronics / repair

author: ym58
author_rank: Regular Contributor
timestamp: May 04, 2022, 11:14:14 am
content: Has anyone been able to modify theOVP levelof theHSTNS-PD18"tiny but powerful"HP Server SMPS ?I have found a bit of literature on how to mod theVoutexcursion range as inHEREbut nothing really relevant to theOVP

author: axm1955@yahoo.com
author_rank: Newbie
timestamp: June 16, 2022, 09:18:58 pm
content: Hello ym58,Did you ever get any answer to your quest? I too sought information about the PD18 as well as the PL11.Modified a PD18 to achieve 13.85V, but the over current protection now kicks in at 25A, so wondered if you had success in finding documentation for I think it will help me too.

author: ym58
author_rank: Regular Contributor
timestamp: June 17, 2022, 04:29:32 am
content: Nada @axm55, to my great despairI'm hoping leaving this topic alive will make hints come as my two PD-18's are now sitting on a shelf !The same with two powerful & tinyEmerson 7001605-J000(aka IBM 94Y8113/8114) ...Do you have any info on this PSU ?

author: coromonadalix
author_rank: Super Contributor
timestamp: June 17, 2022, 02:18:06 pm
content: you may have some infos on RCgroup web page, they hack server psu's to charge batteries ...

author: ym58
author_rank: Regular Contributor
timestamp: June 17, 2022, 02:40:20 pm
content: yes, I've been there but nothing really relevant (especially when it comes to OVP hacking ...)thanks for the tip, however.
HT-Instruments HT 79 Clamp Meter - readings low - zero function behaviour - Page 1
Forum section: electronics / repair

author: soldermarc
author_rank: Contributor
timestamp: August 25, 2024, 10:02:51 am
content: I've got a used HT79 clamp meter here.Some simple dc current measurement tests show values about 10-20% too low.When I press the "ZERO" button in dc current mode the meter tries to zero but after some seconds the "mA" in the display disappears and pressing the "ZERO" button again nothing happens anymore. The meter seems to be stuck and only gets reset out of this when it is powered off and on again.If there is some kind of service instructions available or somebody out there who knows what's going on with the device it would be very helpful. The pcb has a bunch of trimmer pots on the back, but I doubt that only adjusting the correct one solves the problem.

author: fant
author_rank: Contributor
timestamp: August 25, 2024, 11:36:03 am
content: Pictures?

author: soldermarc
author_rank: Contributor
timestamp: August 25, 2024, 12:24:44 pm
content: Found someone worked inside before. VR1 and VR3 were put all into the right position.

author: soldermarc
author_rank: Contributor
timestamp: August 31, 2024, 11:19:00 pm
content: It seems to be the same as AEMC Model 556.https://www.aemc.com/products/clampon-meters/clampon-meter-566I wonder who's the oem for this meter?Perhaps this would it make easier to find more information or a service manual.

author: soldermarc
author_rank: Contributor
timestamp: August 31, 2024, 11:26:41 pm
content: Found more names for the device.KOICO Model 3541https://www.koico.co.jp/product/acdc-clamp-meter-for-low-current-measurements-2/KUSAM KM 2006https://www.kusamelectrical.com/AC-DC-TRMS-Leakage-Clampmeter-KM-2006.htmCentertek CENTER 262https://www.centertek.com/product_d.php?lang=en&tb=1&id=205&cid=52

author: soldermarc
author_rank: Contributor
timestamp: September 16, 2024, 10:58:09 am
content: According to a sticker on the pcb (262-3) the correct oem should be Centertek and the device is a Center 262.No service manual found so far.
HT Instruments HT64 - Page 1
Forum section: electronics / repair

author: fuzzomanus
author_rank: Newbie
timestamp: April 09, 2024, 10:00:35 am
content: Dear people of EEVblog,You are my last hope! Obviously, I have a problem with the meter in the subject and I need help. Here's an intro. I am a proud owner of HT Instrument device shown here:https://www.ht-instruments.com/en/products/digital-multimeters/trms-multimeters/ht64/It's top of the line unit, it has all the bells and whistles including dedicated 4-20mA loop measurement range and rogowski coil range. Heavy and bulky unit with big fat fuses and perfect display with trend representation and data logging.Well, it seems that the perfect screen is not so perfect. Unit is several years old, and in total it was used less than 5 hours (protection film is still on the front of the LCD). It was working normally at that time, and was used only in lab, only measuring some resistors and low voltages. Two years ago it was stashed away in basement in its carry bag. It was recently pulled out of the storage and it doesn't work anymore.My first guess was the battery, but the battery is ok and charged, both fuses are ok, no moisture entered the casing. When the switch is moved into any position other than off, meter responds with a clear beep after pressing any button, but there is absolutely nothing on the screen, so my best guess is that the screen (or the backlight) died and the rest of the instrument is ok. I've opened it up and brought to work, guys at work checked it under a microscope (we are in electronics business), there was no visible corrosion or short circuits anywhere on the PCB, including LCD pins. Guys were clueless what to do next and so am I. I could not find a new LCD with the code that is on the original one. Also, the unit has an exposed JTAG connector inside, but I'm not sure if I can do anything with it. I have bunch of pictures made during disassembly that I can dump here, maybe it's a generic PCB that can be easily replaced. Please help me with my meter, thanks in advance!

author: microbug
author_rank: Frequent Contributor
timestamp: April 09, 2024, 02:37:13 pm
content: I doubt you'll get much help without the pictures!The display looks like a generic colour LCD. It might be possible to find a replacement, but it would be difficult. We would need the part number to search for a replacement.

author: fuzzomanus
author_rank: Newbie
timestamp: April 10, 2024, 10:53:07 am
content: Not a problem, here's a dump of photos made during disassembly. I did find some similar LCDs, but they all have their flat cables on the "wrong" side (shorter side).
HTC OS 5030 OSCILLOSCOPE - Page 1
Forum section: electronics / repair

author: hitecelec
author_rank: Regular Contributor
timestamp: November 04, 2020, 10:35:23 am
content: Hi Allneed part Number/ type of Zener Diode V 35 in the 150 V power supply scetionCan anybody helpThanks in advance

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 04, 2020, 10:52:14 am
content: It might sound like a joke, but the service manual of this oscilloscope only contains the block diagram and no diagrams at all....http://www.mantech.co.za/datasheets/products/OS-5020%5E1.pdfIt is completely ridiculous.So, unfortunately, impossible to help you.Maybe someone who has the same oscilloscope could measure the voltage across this zener diode?Ask for schematics to the manufacturer EZ DIGITAL !http://www.ezdigital.co.kr/a/sub_page.php?page_idx=138

author: Chris56000
author_rank: Frequent Contributor
timestamp: November 05, 2020, 06:07:36 pm
content: Hi!Is this S.M. I have placed in my Dropbox any good for you?https://www.dropbox.com/s/1e3tf7p4ecvdd4n/134639836-LG-OS-5020G-Oscilloscope-Service-Manual.pdf?dl=0Chris Williams

author: hitecelec
author_rank: Regular Contributor
timestamp: November 06, 2020, 06:21:03 pm
content: hello ChrisThanks

author: RAJENDRA
author_rank: Newbie
timestamp: November 19, 2020, 02:54:27 pm
content: Hello,Thanks for your help.sent wrongly service manual of OS9020G instead of OS5020G.could you pl. resend.thanks.

author: Chris56000
author_rank: Frequent Contributor
timestamp: July 20, 2021, 01:41:48 pm
content: Hi!Sorry for being so long researching this, but I've found a set of diagrams for you!They've been drawn in some awful Asian cad software and the lettering and numbering is absolutely barbaric to read, but it's the best I can do until I can afford to buy one of these instruments myself and draft a proper service manual for you – all the secondhand ones are in the rotten u.s. and the import and shipping charges are prohibitive!Chris Williams

author: Chris56000
author_rank: Frequent Contributor
timestamp: July 20, 2021, 01:44:26 pm
content: Hi!LG5020G Oscilloscope, remainder of the diagrams. . .!Chris Williams
https://healthperfect.net/alpha-titan-testo/ - Page 1
Forum section: electronics / repair

author: Unknown
author_rank: Unknown
timestamp: December 17, 2019, 09:07:11 am
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: m3vuv
author_rank: Super Contributor
timestamp: December 17, 2019, 09:26:53 am
content: how about banning this asswipe for spam,come on mods get your shit together!

author: Simon
author_rank: Unknown
timestamp: December 17, 2019, 10:22:14 am
content: Sorry for not coming immediately to the rescue. Got home last night with a temperature and am managing to get some stuff done today.

author: m3vuv
author_rank: Super Contributor
timestamp: December 17, 2019, 10:32:54 am
content: wishing you a speedy recovery in time for xmas,73
Huawei e5573 battery replacement  - Page 1
Forum section: electronics / repair

author: wawinfo
author_rank: Contributor
timestamp: April 03, 2024, 08:18:05 pm
content: Hi friends. I have a Huawei e5573 4G router that works on battery like attached photo, unfortunately I can't find that battery and some how I want to use another brand like Samsung battery or maybe unbranded one, Can any one tell me about that two unknown pin on Huawei battery?I know in some manufacturers there is a temperature ntc type sensor pin to tell the phone about temperature of battery while charging, and for that type I can emulate the ntc pin, but here are two extended pins, and I couldn't find any pinout and specifications about that, I will appreciate your help in advanced
Huawei Mate X Pro 2020 Voltage regulator blew - Page 1
Forum section: electronics / repair

author: lmagalhaes
author_rank: Contributor
timestamp: September 27, 2023, 06:30:51 pm
content: Hi there,I have a Huawei Mate X Pro 2020 that has stopped working. When I opened it up, I saw that one of the voltage regulators absolutely desintegrated. However, looking around the same area of the board, I found another regulator with a similar marking and footprint. However, googling it I couldn't get to the same part.Here is a picture:I came across some other components on aliexpress but aren't MPMJ, they are MPxx (examplehttps://pt.aliexpress.com/item/4001037315185.html?gatewayAdapt=glo2bra). Also got to a Monolithic Power Systems part, but their markings have MPS on the first line, so I don't know if that is the correct part. However, the footprint is very similar (https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP86945A/).If anyone can help me identify this part, I-d be very appreciated. Hopefully, replacing this regulator will return the laptop to life.
Huawei OEM spare parts - Page 1
Forum section: electronics / repair

author: den
author_rank: Contributor
timestamp: September 15, 2019, 01:16:15 pm
content: Hi everyone,anyone has any info/experience on where to get an original Huawei P10 display? A lot of options generally, but most of them look fake, no idea how to tell if it is OEM (people say that fake ones are worse in many ways).The best options I have found are:https://www.witrigs.com/oem-lcd-screen-with-digitizer-for-huawei-p10-graphite-black#customer-reviewshttp://www.mobilelcddisplay.com/original-lcd-for-huawei-p10-display-touch-screen-replace-replacement-vtrl09-p-2081.htmlhttps://eshop.instamel.com/index.php?id_product=50&id_product_attribute=0&rewrite=oem-screen-with-frame-for-huawei-p10-black&controller=productThere also are two options - with frame and without frame. No idea if OEM actually are offered in both variants. Any advice on which is better to get is welcome (is saving 30 Eur worth the hassle?).Den

author: YetAnotherTechie
author_rank: Regular Contributor
timestamp: September 15, 2019, 11:40:28 pm
content: Always get it with the frame, otherwise you need to be able to un-glue and glue back the screen/digitizer, you can search for videos of this process, it needs a machine, otherwise crap results and a broken display is certain. youtube "In frame whole phone laminating mold for Samsung s7" for example.

author: den
author_rank: Contributor
timestamp: September 16, 2019, 04:15:28 am
content: Thanks YetAnotherTechie.Any info on OEM parts? Anyone?
Hum appeared in valve amp (C-J MV-55) - Page 1
Forum section: electronics / repair

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: January 10, 2024, 08:27:26 pm
content: My MV-55 has developed a hum equal in both channels. On this amp the output tube bias is set with a pot by each tube with an indicator LED. They're all trimming mid-range which is correct.If the bias is wound down the hum disappears, suggestign that it's coming in from the earlier stages of the amp (12AX7 and 6SN7).Tried rolling all tubes to rule out any obvious issues.HT all looks fine, with minimal ripple.So, to the heater supply: this consists of one winding which provides AC to the four parallel heaters on the output tubes, and then is bridge rectified (discrete 1N500x type) and smoothed (4700µ) which then feeds the small signal tubes with DC.The DC heater supply is referenced to the HT ground (via a 220k resistor and parallel cap), but I do not believe this is relevant (the line disappearing off in the schematic belowMeasurements show, however, that on the supposed DC supply I've got about 4V DC plus 1.2V AC superimposed. This rail when 'scoped shows the 1.2V RMS AC at 50Hz (UK) not 100Hz.This suggests to me that I have a duff rectifier diode, presumably open circuit? Am I on the right path?It's so simple I cannot see what else could be wrong...All guidance appreciated. Thanks.

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: January 10, 2024, 08:55:07 pm
content: Answering my own post, I find that my MV-55 has a fuse in the heater winding circuit so by removing the EL34s I can test the rectifiers avoiding a complete engine out.Result - one is o/c.
Humidifier-Stopped working, no mist! how to test Piezo? - Page 1
Forum section: electronics / repair

author: Aakash
author_rank: Contributor
timestamp: December 01, 2021, 05:12:01 pm
content: My humidifier stopped working, there is no mist coming out of it. I can hear the fan is running.Can anybody let me know how can I check if the piezo is working or if I should replace the piezo.Any suggestions please help.

author: Haenk
author_rank: Super Contributor
timestamp: December 03, 2021, 11:17:04 am
content: Not sure if this works, but maybe use a laserpointer and the piezo element as a "mirror" and project the laser dot. If the projected dot gets broader, when the cleaner is switched on, the piezo is working.

author: wraper
author_rank: Unknown
timestamp: December 03, 2021, 11:27:28 am
content: Replacing transducer most likely won't help since the problem most likely is in electronics which are driving it. Unless it's electrically shorted or has visually observable damage, not likely there is anything wrong with it.

author: Xenon
author_rank: Contributor
timestamp: December 03, 2021, 04:31:00 pm
content: Those piezo thingies are also used in medical humidifiers. They fail when they run dry because of overheating (they are driven hard).Often the failure is visible on the piezo surface. It has a discoloration in the center or the surface peels off (tiny blisters).Do you see anything similar?

author: Aakash
author_rank: Contributor
timestamp: December 03, 2021, 06:06:30 pm
content: There is no discoloration that I see of, is there any way to drive it externally with a function generator and get to know if it's working fine?

author: james_s
author_rank: Super Contributor
timestamp: December 03, 2021, 06:17:04 pm
content: You could connect it to an audio amplifier, piezo elements are very commonly used as inexpensive tweeters.

author: Aakash
author_rank: Contributor
timestamp: December 03, 2021, 08:23:59 pm
content: I don't have any idea to build an audio amplifier, do you have any base circuit that I can build?

author: james_s
author_rank: Super Contributor
timestamp: December 03, 2021, 08:56:29 pm
content: Build? If you take 10 seconds to search with google you will find numerous circuits, but surely you already have some kind of audio device around? Or just buy a small amplifier module, you can get them for a few dollars or less.

author: Renate
author_rank: Super Contributor
timestamp: December 04, 2021, 01:36:42 pm
content: I say that if it looks good, connect it to your scope and tap it lightly. You should see plenty of volts.
Humidity Sensors - Page 1
Forum section: electronics / repair

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 07, 2023, 05:31:48 pm
content: With humidity sensors, I know they tend to fail over time as the surface gets contaminated. I saw in a data sheet for one sensor a method of recovering was to heat it up to 90 ish degrees for 20 mins or so.Is this a known method for recovering sensors? Does it work on most sensors?I ask as I have one in the lab that has a linearity issue so I would like to see if it can be recovered rather than replacing the sensor. But I also get the odd one in that you can tell is in a dusty room and could do with a clean.
Humminbird 385CI - switching diode SOT-23 - Page 1
Forum section: electronics / repair

author: Travis79
author_rank: Newbie
timestamp: November 03, 2019, 09:11:04 pm
content: Hi there!I wonder if here is anybody who could give me a hand with my issue.I'm trying to repair my Humminbird 385CI fish finder.Beside the SA604A replacement, I discovered that switching diode has been blown/burned.The question is quite simple. How can I define what switching diode it was?The only information I got from Humminbird support is that it is switching diode and it is SOT-23 form factor.It is located directly on the Vcc path, right on the input path from the battery.I assume it functions as a fuse, right?The technical specification of the unit says, that its current draw is 425mA.I'm desperately looking for the switching diode with forward current around 500mA, but having no luck. Mostly they are rated 250 mA max.Am I looking for the wrong rating of the diode or is it really so hard to find such diode?Does it mean that the switching diode doesn't have be rated >250 mA with such unit current draw?Unfortunately I was not able to get schematic of the boardI'm attaching picture to show the reality at least.I'll appreciate any advice.Thanks!

author: fzabkar
author_rank: Super Contributor
timestamp: November 03, 2019, 09:45:56 pm
content: It looks like a reverse polarity protection diode, probably Schottky. It doesn't appear to have any switching function.I would just use any Schottky diode that fits, even a 2-pin type. Diodes which are rated for higher currents will have a lower voltage drop.That said, I would be concerned about possible damage downstream of the diode.Edit: Maybe I'm wrong, but could the diode be a back-EMF protection diode connected across the primary winding of T401?

author: Travis79
author_rank: Newbie
timestamp: November 04, 2019, 08:02:53 am
content: Hi fzabkar,Thanks for your thoughts.My initial idea was to replace it by Schotkky diode as well, but I decide to ask others for their opinions as well as it is an issue I don't understand exactly but would like toIf I did the measuring correctly, the diode is in series only. No parallel connections to it.It shares the two pins on one side and outputs one to the other side.If I would like to replace is by the "original", did you see any with proper parameters anywhere around?Cheers, Travis

author: fzabkar
author_rank: Super Contributor
timestamp: November 05, 2019, 04:24:11 am
content: Could you show us the other side of the PCB?

author: Travis79
author_rank: Newbie
timestamp: November 05, 2019, 08:56:47 am
content: Sure, but as one can expect, the PCB is multilayered

author: fzabkar
author_rank: Super Contributor
timestamp: November 05, 2019, 08:53:23 pm
content: Sorry, I can't make out where the diode goes.If it's in series with the Vcc supply, then it would be a common cathode, dual diode, not necessarily a switching type. If it is a back-EMF snubber diode connected across the transformer primary, then it would be a dual, common anode, switching type (with a lower current spec).In either case I would still be concerned about damage to other nearby components.
HUNG CHANG 5502 vertical section problem - Page 1
Forum section: electronics / repair

author: EP3SK
author_rank: Newbie
timestamp: January 25, 2021, 05:36:40 pm
content: Hi , i have problem with my oscilloscope HUNG CHANG 5502 in its vertical section. once powered on and then the screen of oscilloscope was showing that its vertical beam is not working properly. device opened and i found Q307 , Q309 , Q311 are defected. changed with near same parameter B649 and D669 as the same TR were not available in my country. it was working for 3 days and after a while working it get damage again on the same TRs . please advise if you have experience about this problem .

author: EP3SK
author_rank: Newbie
timestamp: January 25, 2021, 05:39:13 pm
content: the service manual attached
Hung Chang 5504 aka Beckman Philips Protek Tenma Oscilloscope - Page 1
Forum section: electronics / repair

author: trueblue2k2
author_rank: Newbie
timestamp: April 20, 2021, 05:10:17 am
content: Hung Chang (Korea) series of mid-1980s oscilloscopes was made in 20, 40, 60, and 100 Mhz models, selling under Hung Chang, Protek, Beckman, Philips, Tenma, or other names. The 40Mhz Hung Chang 5504 sequence may be: (5) inch screen size, (5) 198 year, and (04) Mhz X10 rating. It has an off-white faceplate re-branded Beckman Industries 9104 or Protek 5504; or else a black faceplate as Philips PM-3209 or Tenma 72-740. "Instruction Manual" included by Hung Chang includes schematics, parts, and calibration adjustment control info. Link for Hung Chang 5504 manual:http://www.i1epj.ham-radio-op.net/Laboratorio/file/HC5504%20Manual.pdf

author: ssschuh
author_rank: Newbie
timestamp: May 27, 2021, 01:42:57 pm
content: The link seems broken.This one works.http://www.i1epj.ham-radio-op.net/Laboratorio/files/HC5504%20Manual-LoRes.pdfThanks for sharing, I'm looking for the 5804 diagrams.But looking at the horizontal and vertical boards on the 5504 manual (and also the 5602 that I had), they are the same as the 5804.Unfortunately, my unit has a CPU board also, controlled via little buttons and leds on the front pannel, instead of physical the switches controlling vertical/horizontal/sweep mode. These controls are locked on ch1, so I need that circuit diagram too in order to fully repair it.It has also other problems, like no sweep at all, even with external source, so I guess I have to diagnose the z-axis circuit.And sometimes the dot faints, even though read out info shows always fine, so I suppose it's some z-axis input circuit issue.

author: linux-dude
author_rank: Newbie
timestamp: May 30, 2022, 06:51:11 pm
content: I'm also looking for schema for 5804. Did you ever find it?Sorry for resurrecting a dead thread.

author: ssschuh
author_rank: Newbie
timestamp: April 14, 2023, 01:27:36 pm
content: I don't think the thread is dead, at least I'm still looking for info on HC5804.I could find some rebranded specific models, but couldn't find any circuit or manual for them either.The models are Tenma 72-925 and Protek P-2840.I still couldn't find the rebranded models from Philips and Beckman.
Hunting short - Page 1
Forum section: electronics / repair

author: diskosteppas
author_rank: Contributor
timestamp: September 26, 2021, 11:55:57 am
content: Hi all Ive got my drum machine open and it with it not powering up, I opened it to check voltages.Power board connected to mainboard, Checking 7905 it gives out of spec reading.Disconnecting the psu board from mainboard the 7905 returns to spec.Checking mainboard, some IC's are hot. Caps seem ok. No other obvious damage.I removed the 3 hot IC's and the 7905 is within spec again.Is it safe to assume one or all of these parts are at fault please?

author: Manul
author_rank: Super Contributor
timestamp: September 26, 2021, 02:08:12 pm
content: Quote from: diskosteppas on September 26, 2021, 11:55:57 amEverything is a guess until something is proved. Something connected to the output of these ICs could be shorted, so the ICs get hot. I would say your guess is a good guess, but it is not a safe assumption. Also it is a bit suspicious, that 3 ICs got damaged at once. It is possible, but not super likely. So you may buy them, replace and hope, or you may spend some more time and collect more information.I don't know what kind of chips you removed, but your options might be checking supply pins of IC with multimeter (burned ICs sometimes have them shorted), try to power them outside the circuit. Get datasheet, see what IC does, trace and check inputs/outputs on the board. Many options.

author: DavidAlfa
author_rank: Super Contributor
timestamp: September 26, 2021, 02:49:15 pm
content: I'd lift the 7905 output pin and put the amp meter in between.Probably at least one IC is overloading the regulator.Knowing the regulator has a limit of ~1.5A, note down the the readings without these ICs.Then put back one IC at a time. If any causes a huge current flow, you found the culprit.If after soldering all back the current isn't too big, then you could blame the regulator.

author: diskosteppas
author_rank: Contributor
timestamp: September 26, 2021, 04:09:17 pm
content: I did not think to test current draw per IC at a time. I'm going in. Thanks for the tip!
Huntron Switcher 640  - Page 1
Forum section: electronics / repair

author: Martin Miranda
author_rank: Regular Contributor
timestamp: January 06, 2022, 03:08:33 pm
content: got this equipment for free, got really excited that it would be like a huntron tracker. when i got home i realized it has a LCD instead of the usual CRO or LCD screen.... upon a quick google it's a extension for huntron trackers for "automating", and no amount of google fu that i can find the service manual or schematics.so i took a look at the schematics of huntron tracker 2000 instead. and how it feeds signal to the switcher.upon closer inspection it uses a 8051 mcu and a ADC... the tracker only sends the sine wave and a ttl output clock. making me think that this is a independent machine. (so i fed in a 60hz 7.07 Vac rms signal) the sync from the signal gen to the clock input. and it worked!

author: Martin Miranda
author_rank: Regular Contributor
timestamp: January 06, 2022, 03:14:18 pm
content: - power is supplied by the huntron tracer... split 12vdc.- clock is mentioned in the manual that feed to the switcher.
huntron tracker model HTR1005B-IES psu transfo - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: July 14, 2019, 09:22:51 pm
content: Hi all i have the above piece of gear its been left in the damp and the psu transformer has gone open on the 240v primary,it looks like 6 wires go in one side and 6 in the other,i presume one side is primary and the other the seconderys,would anyone have any info on this unit,ie schematic or service manual etc,i want to homebrew another psu for it if poss but without any info im in the dark,thanks in advance paul. m3vuv

author: pbarton
author_rank: Frequent Contributor
timestamp: July 15, 2019, 05:43:49 pm
content: Free service manual with full schematics herehttps://www.opweb.de/en/model.php?id=10657scroll down and click on 'free download' button.You are right the transformer has a total of 12 wires. However, 3 on the primary and 9 on the secondary.Looks like the same transformer 06-6032 is used in the tracker model 2000http://huntron.com/forum/index.php?topic=72.0
huntron tracker psu replacement - Page 1
Forum section: electronics / repair

author: p.larner
author_rank: Frequent Contributor
timestamp: December 08, 2023, 06:29:15 am
content: i have this tracker and killed the main psu transfo,i need the following voltagesThe power supply section provides various operating voltages:(1) -1350 Volt Regulated High Voltage.03, 04, C9, C10, C11, C12, R46, R47, R48, and R49 form a voltage doubler; Q7 and IC2 providelinear voltage regulation. For adjustment details see Internal Set-Up and AdjustmentsSection.(2) + 180 Volt Unregulated Deflection Voltage.Diodes 05,06,07, and 08 form a full wave bridge rectifier, and C14 is the filter capacitor.Bleeder resistor R57 discharges voltage in C14 to a safe level within 60 seconds after poweris turned off.(3) + 6/-6 Volt Regulated Voltage.Diode 09, 010, 011, and 012 form a bridge rectifier; IC3 and IC4 provide regulation for+ 6 Volt and -6 Volt respectively.(4) 6.3 Volt Filament Voltage.The power transformer supplies this voltage to the filament of the CRT.Switch SR5 sets up power transformer TR2 for 220 Volt or 240 Volt environments in the EuropeanEconomic Community.,any ideas how to fix it maybe using moduals,the transfo is no longer made/available.

author: Chris56000
author_rank: Frequent Contributor
timestamp: December 10, 2023, 05:47:47 pm
content: . . .As you're shown as UK Based, register on the UK Vintage Radio Forum if you're not already a Member, and contact Ed Dinning – he can rewind the transformer to the exact voltages for you – it will, I'm afraid, cost £100 or so, but that's peanuts when you consider the absolutely obscene prices sellers are asking for these things!. . .I bought one of the Chinese TSH210s and use it with a small Unipart schools oscilloscope!. . .If you don't mind the small display, you can get the Chinese NSU–210 that does the same job for £100, free p & p, or, you could buy the AliExpress NU–210 for £27 plus tax and postage, and get a small cheap CRT oscilloscope off ebay to provide the display!Chris Williams

author: BobBeBob
author_rank: Regular Contributor
timestamp: March 23, 2025, 12:10:05 am
content: which huntron do you have. did you ever get it done?

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: March 24, 2025, 06:45:30 am
content: Hello p.larner,The link to the maintenance manual seems broken (error 404)
HVAC Blend Door Actuator motor test - Page 1
Forum section: electronics / repair

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 03, 2023, 08:50:12 am
content: Hi,This HVAC blend door motor actuator was removed from a Volvo car. It's responsible for changing the damper from heat to cold and vice versa. It has 3 pins.1 pin red = voltage2 pin purple = frequency3 pin black = ground.How can I test this motor on my bench with external PSU? The problem here is the frequency. How can I feed a frequency to rotate the motor?

author: amyk
author_rank: Super Contributor
timestamp: July 03, 2023, 08:57:24 am
content: That's actually a Ford part, but you'll probably need a signal generator to produce the right (PWM?) signal; likely similar tohttps://en.wikipedia.org/wiki/Servo_control.

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 03, 2023, 09:28:55 am
content: Thanks for the reply. I just want to make sure it works fine, unfortunately, I don't have a function generator. Can I try using a custom FG using ie Arduino PWM? Will this work?1pin = 12V supply2 pin = PWM3 pin = GND

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 03, 2023, 07:44:01 pm
content: I finally opened the box. It seems that has a motor controlled from an IC named ELMOS 14301B. No datasheet found. Any infos about this? Does this motor controller is uniquely programmed to be used only for the mached VIM? How this motor is working and how can I test it?

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 03, 2023, 07:46:22 pm
content: Extra Photos

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 03, 2023, 07:50:28 pm
content: Photos...

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 04, 2023, 05:40:33 am
content: I made a first unsuccessful try.With external power supply I connected 12V to Red line and Ground to black line. Using my GM328 tester, I connected the purple (pin2) line with the PWM output of the GM328.I verified with my DMM the duty cycle of the GM328 output but nothing, the motor didn't move. The grounds from the PSU and GM328 were connected to create a common ground.Any other ideas?

author: Dan N
author_rank: Contributor
timestamp: July 04, 2023, 01:59:39 pm
content: You didn't give the year, but this old article from 2000 describes the different types of actuators and how they are controlled:https://www.motor.com/magazine-summary/diagnosing-electronic-climate-control-actuators-april-2000/Most likely the third wire is a sensor output.