hybridfree/eevblog-posts huggingface dataset:
Blown input diodes on Uni-T UT622E LCR meter - Page 1
Forum section: electronics / repair

author: nekelly
author_rank: Newbie
timestamp: March 15, 2023, 11:39:16 pm
content: Hello all, first post here 🙂This evening I accidentally connected 12v to the input of my month-old (🥴) LCR meter and I heard a pop. I opened it up and found 2 blown diodes. I can replace the M7 ok but I've no idea what the orange/black diode is as it appears to have no markings. Any thoughts? Simple diode or zener maybe? Pic attached.Thanks, Noel.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 16, 2023, 02:27:17 am
content: maybe 1N4148 ??Do you have an dmm, and a diode test functioncheck the one on the photo who seems physically ok you should have 0.6v in a direction and way higher or infinite in the other way, but the circuit could play a trick

author: nekelly
author_rank: Newbie
timestamp: March 16, 2023, 03:19:01 pm
content: Yes, I checked the good one with a DMM and it read 0.56 in the forward direction so I replaced it with a similar one from a laptop board. Hopefully it's ok now!As an additional check, I put a resistor in series with the good diode and reverse biased it to see if it acted like a zener and there was no breakdown up to 30v.What originally happened was I touched the test leads to a 12v battery thinking the leads were connected to my DMM but they were attached to my LCR meter. Big whoops!

author: Kleinstein
author_rank: Super Contributor
timestamp: March 16, 2023, 07:15:03 pm
content: With 2 back to back diodes it would not make much sense to use zener diodes. With only 0.56 V this looks like a stronger (higher current) diode than a 1N4148. Chances are the diodes are for protection and there could be additional, not so abvious damage. With a weaker diode the protection would be weaker.

author: gamalot
author_rank: Super Contributor
timestamp: March 17, 2023, 03:56:59 pm
content: It's hard to tell, but at least the glass case looks like a 1N4148, if it's not a zener.We all know that the forward voltage drop of the diode will change with the current, and the figure I found in Vishay's datasheet and the results I measured with my multimeters all prove that the test current change from 0.5mA to 1.5mA will have a great impact on the forward voltage drop of 1N4148.
Blown mosfet. - LP9435LT1G - Page 1
Forum section: electronics / repair

author: U298257
author_rank: Newbie
timestamp: May 08, 2024, 04:19:31 pm
content: Hello peeps,Any idea where I can get 1 on these lolIt’s blown from a battery charger.P94 soc-23 from my limited understanding of SMDs.

author: fzabkar
author_rank: Super Contributor
timestamp: May 08, 2024, 05:18:36 pm
content: P94 = LP9435LT1Ghttp://markingcodes.com/search/c/p94https://uploadcdn.oneyac.com/attachments/files/brand_pdf/lrc/BE/FF/LP9435LT1G.pdf(datasheet)https://www.platan.ru/docs/library/2018LRC Product Catalog.pdf(catalogue)https://ae01.alicdn.com/kf/S8edf08093ca7429998a7f1709389f9fcx.png(photo)

author: wasedadoc
author_rank: Super Contributor
timestamp: May 08, 2024, 05:18:50 pm
content: SOT-23https://alltransistors.com/mosfet/transistor.php?transistor=42446

author: U298257
author_rank: Newbie
timestamp: May 08, 2024, 06:33:55 pm
content: Does anyone have a couple LP9435LT1G?I really done fancy having to buy a roll of 50 - 1000 haha.

author: MathWizard
author_rank: Super Contributor
timestamp: May 12, 2024, 06:44:40 am
content: What's it from ? The datasheet doesn't look super magical, but IDK mosfets that well. There's probably some cheap ebay ones that would do ok, and there's probably ebay ones that would do just fine. Then there's trying to search on the Digikey and other places, by spec's. If it's just some basic slow switch, probably anything with a small enough VGS threshold should do, and similar current and Rdson values.

author: U298257
author_rank: Newbie
timestamp: May 12, 2024, 08:34:20 am
content: Hi,I bought 50 of them from AliExpressSo if anyone needs a few let me know.It’s from a li-ion battery charger.

author: loulou31
author_rank: Contributor
timestamp: May 13, 2024, 11:57:09 am
content: Hi,Thank you for the proposal .... However I am not very confident on Aliexpress active components : there are a lot of fakes....RegardsJean-Louis
Blown SMD cap - how to find value - Page 1
Forum section: electronics / repair

author: born2fly2
author_rank: Newbie
timestamp: July 19, 2020, 07:56:10 pm
content: I was wondering what the best method(s) are when you are trying to determine the value of a blown SMD cap and there is no labeling or schematic.

author: TheMG
author_rank: Frequent Contributor
timestamp: July 20, 2020, 12:08:03 am
content: You either try to find another identical board with a known-good cap to measure the value, or you come up with an educated guess based on what the capacitor is doing in the circuit, its operating voltage, and physical size.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 20, 2020, 03:54:31 am
content: That's basically it. If it's part of a circuit around a primary part (like an IC) you can take a look at the chip's datasheet to see recommended values, as designers will often follow those guidelines. If it's a bypass cap the value is probably less critical, and you can match it to other similarly sized bypass caps on the board (since they probably have some standards used for all the bypassing on the board). If it's part of an analog network or the value/specific parameters really count, unless there's a copy of that circuit elsewhere on the board or on another board, you basically have to reverse engineer what it's doing to try and get a good guess for the cap picked.

author: born2fly2
author_rank: Newbie
timestamp: July 20, 2020, 02:58:26 pm
content: Ok, I kinda figured as much, I just wanted to see if there was a better way. So I can still assume then that if you guess wrong, "pop goes the capacitor' is possible.
Blu-ray player repair or beyond economical repair - Page 1
Forum section: electronics / repair

author: jonovid
author_rank: Super Contributor
timestamp: May 31, 2022, 10:29:00 am
content: I was given a non-working Laser BLU-BD3000 Blu-ray player for free by a neighbour.https://assets.kogan.com/files/usermanuals/LSR-BLU-BD3000.pdfmechanical inspectionthe Blu-ray player hand been heavily used in a smoky room as it was coated with black dust and or tobacco smoke residue,fingerprint residue did show the buttons most used on the remote.it will boot up and play USB media files ok but only in 480p standard definition video, even from the HDMI output.did cleaning of the lens and vacuum'd all the insides of the drive bay.my question is about the Blu-ray player common mechanical problems. that other may know about?the BLU-BD3000 Blu-ray player tray will take a disc and load it as will, as also eject the disc ok.the fault is this.however when the spindle motor spins up the disc to speed a grinding noise is heard.at maximum RPM- revolutions per minute. may be a spindle motor hub alignment problem? or head to disc contact - physical touchinghowever no contact scaping is seen on the Blu-ray discthe mico automaticity spins the disc RPM down and then re-spins up the disc to speed.also the tracking servo system motor kicks in trying to find the start track on the Blu-ray disc.the mico automaticity spins up the disc 3 times before quitting.the lens shows blue laser light. when the top spindle clamp assembly is removed from the drive tray assembly.I have re-oiled the tracking servo jack-screw and the tracking bar or rod.I have not re-seated the ribbon cable plugs. is this a common problem?maybe the fine lens tracking, a lens focus fault?looks to me like deteriorated plastic parts is the course of the fault in the lens assembly.maybe lens assembly has been out of focus with the disc or maybe the hub alignment is coursing a disc to case contact scraping problem.has anyone else tried to fix a Blu-ray player with this type of fault? any success story's to tell?or is it all beyond economical repair.

author: Haenk
author_rank: Super Contributor
timestamp: May 31, 2022, 01:52:38 pm
content: IMHO not worth the effort.Optical drives don't like smokers' homes at all. The plastic lenses might even suck up the tar, this might be the problem here.Buying a replacement laser is probably the solution, but will cost almost as much as a new cheapo BD player. Plus you still have a smelly, old, nicotine-covered device, that is not worth any effort.

author: David_AVD
author_rank: Super Contributor
timestamp: May 31, 2022, 09:14:27 pm
content: It will be a bin job IMO.

author: jonovid
author_rank: Super Contributor
timestamp: June 01, 2022, 05:58:48 am
content: Ok I get it
Blue Yeti microphone Rev.7 firmware file (EEPROM; Arduino) ? - Page 1
Forum section: electronics / repair

author: Ivan_s_Lab
author_rank: Newbie
timestamp: July 09, 2020, 11:20:19 pm
content: Greetings, I have a Blue Yeti with a revision 7 digital PCB with a corrupted EEPROM. Now this version of the Yeti is notorious for losing its firmware when connected to certain USB ports. Basically it uses a UAC3576B ADC which reads its firmware off a 24c128 EEPROM. Now I've had a few of these mics but they were all different revisions which use different ADCs so their firmware is not compatible with the revision 7 board. I don't have an EEPROM programmer but I do have a few Arduino boards that I can MacGyver into one. So If anyone has had this issue and still has the firmware file stored somewhere I would be very grateful if they can share it. Thank you in advance.
Blueair sense + air purifier motion sensor issue - Page 1
Forum section: electronics / repair

author: moss99
author_rank: Contributor
timestamp: June 10, 2022, 09:40:37 am
content: Hi , I have a blueair sense +air purifier which operates by waving your hand over the top , I got it apart and removed the board with the sensor on , it all seems fine and operates fine up to a distance of 6 - 7 inches away but when it goes back behind the glass it does not work , any ideas anyone , here is a photo of the sensor , seem like 2 led's and a sensor , not quite sure how it works .
Bluetooth Ear Buds (Prime Brands) - Page 1
Forum section: electronics / repair

author: IRB
author_rank: Regular Contributor
timestamp: May 11, 2022, 12:45:46 pm
content: I receive a pair or Prime Brands NFL ear buds as a gift. Turns out they were duds not buds. I reached out to Prime brands it took less than 3 weeks they shipped me a replacement pair at no charge. The replacement ones look more like apple ear pods.I am hoping some one can help me fix the original ones as I found them more comfortable.There are a few unpopulated parts I think the SOT-23 is the important missing part, I am not certain but I think it is in the negative feed from the battery.Also if any one can point me to the data sheet for the chip may be there is a sample circuit.JL "UEB094" I could not find the chip athttp://www.zh-jieli.com/

author: tooki
author_rank: Super Contributor
timestamp: May 14, 2022, 04:01:26 pm
content: What gave you the idea that the unpopulated parts are the cause of the problem? It’s very common for there to be unpopulated component footprints in products.

author: IRB
author_rank: Regular Contributor
timestamp: May 16, 2022, 12:01:38 pm
content: It's just a guess. The person I spoke to at the company said is was an issue with the battery. They were unclear if it is a charging issue or a not holding a charge issue.It could be an issue with the battery itself, and nothing to do with the PCB. There are two chips on the battery pack.
Bluetooth speaker goes into protection when powered up - Page 1
Forum section: electronics / repair

author: bogdan2014
author_rank: Regular Contributor
timestamp: November 11, 2021, 10:04:10 am
content: I have an Akai battery powered speaker (the larger ones with a 10 inch woofer) and when powered up it goes into some sort of protection. I can hear the relay click rapidly a few times and the woofer popping but then it shuts down. It only does this with the woofer connected, if I disconnect it it powers on normally. I double checked with another driver and it does the same thing. So I suspect either:- the TDA7377 chip- the speaker protection circuitI'd be really happy to hear some opinions before replacing the chip
BM235 DC screen (mostly) blank - Page 1
Forum section: electronics / repair

author: jstuart
author_rank: Newbie
timestamp: November 05, 2024, 02:00:36 am
content: Fired up my eevblog bm235 the other day and found the dc screen was missing all the numbers. Batteries are ok. (I changed them just because I know you'll ask. No leakage to report.)[ Attachment Invalid Or Does Not Exist ]The volts ac screen looks normal. Cycling through the DC ranges I see blank (auto), blank, -55.03, -550.3, 0L. mV dc appears to work normally, but I don't have a mV reference handy to confirm it's accurate. The rotary switch seems fine mechanically. Again, batteries OK. Innards look clean.Any suggestions how to trouble shoot?Much thanks,Jeff
BM235 disassembly - Page 1
Forum section: electronics / repair

author: andymcl
author_rank: Newbie
timestamp: January 27, 2021, 09:50:56 pm
content: I need to disassemble my BM235 as a mud wasp has filled a connector hole with mud (as they do). To remove the top board do I have to unsolder the short wire or does it pull free. See attached picture

author: andymcl
author_rank: Newbie
timestamp: January 28, 2021, 07:49:40 am
content: Well I managed to clean the socket but seem to have caused another problem in the process. It is now dropping a segment on each digit in the display as per attached photo

author: shakalnokturn
author_rank: Super Contributor
timestamp: January 28, 2021, 09:55:15 pm
content: If you're lucky you've trapped a crumb between the zebra strip and LCD or PCB, if you're unlucky the microcontroller has been hit by ESD.Watch out for screws also: Tight enough is good, too tight is bad...

author: andymcl
author_rank: Newbie
timestamp: January 30, 2021, 10:48:30 pm
content: Thanks for the advice. Full tear down, clean and all working again!

author: MathWizard
author_rank: Super Contributor
timestamp: January 31, 2021, 06:50:52 am
content: I have a BM235 and sometimes it kept have a short on the battery as I turn the knob. I took it apart once and might have some solder balls, but IDK, I think I've still had the problem, of turning the knob and getting the flashing low battery signal, that I'd expect from some short pulling the battery way down.
Bm235 Select button issue - Page 1
Forum section: electronics / repair

author: DocJones
author_rank: Newbie
timestamp: April 23, 2020, 02:12:41 pm
content: I understand someone has had this issue before as the button beeps but cannot change existing modes except backlight unit appears stuck in ac volts, capacitance and resistance. I am unable to select continuity or diode check.Was there a resolve for this .ThanksAny info on this would be appreciated
BM235 voltage measure fail - Page 1
Forum section: electronics / repair

author: beni8910
author_rank: Newbie
timestamp: October 01, 2019, 03:13:49 am
content: Hi, I have just bought a couple of bm235's last week and it appears that one has gone faulty. It will not read voltage anymore although it does still work in continuity mode. I was using it to test a flickering light fault (240Vac) on REC to see the highs and lows when it gave up. I was also using the LoV to see if it gave any different readings.I'm not 100% sure if I've used it incorrectly by testing a known live source with LoV or if this is ok?

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 02, 2019, 09:37:46 pm
content: Bad on all Volt ranges AC and DC?
BM257 (Elma) in DC Voltage (Auto) - Just pulses the "bargraph" - Doesnt show 12v - Page 1
Forum section: electronics / repair

author: bingo600
author_rank: Super Contributor
timestamp: October 02, 2024, 03:53:52 pm
content: My (out of support) Elma BM257 had developed a weird error, while stored.When switching to DC Voltage , it just pulses the "Analog bargraph" , and just hangs there.I tried to connect the probe pins to my PSU set to 12v , but it just kept on pulsing.If i manually try to switch the ranges , then at one of them it shows 0.00v , the rest OL.None of the ranges vill detect the 12v connected to the probes.Other functions work fine - Ie. Ohm shows 0.001 when shorting the test leads.I don't see any "Cal errors" when switching to DCvAny hints ??
BM869 Repair - Page 1
Forum section: electronics / repair

author: Cagatay
author_rank: Newbie
timestamp: February 03, 2025, 10:24:21 am
content: I have a bms869 that broke down with high current measurement. The fuses are burnt, but the protection diodes and transistors are intact. I replaced MCP602 (u15) and UMT2907A (q11) because they were broken. Unfortunately, the device did not work. The screen didn't even come on. When I applied 3.5 and 5 volts from some points on the motherboard, the screen appeared and I read absurd voltage values.Where do you think the problem is?
BMW/Philips 2002 Z8 multi-info radio problem? - Page 1
Forum section: electronics / repair

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: May 30, 2024, 12:15:13 am
content: Radio BMW part number 65.12-6 910 448 Philips part number 9022 247 00231 03 Philips model 22DN700/23B.Radio will not power on, red LED on right side flashes, has some internal voltages but need to know what should be where.Bsp452 has 13.8V on pin 4, 0.6V on pin 1, nothing on pin 3, I need more info.Service info anyone? Operators manual? Vehicle manual shows different units not this one.Is Philips europe still around in germany?Thanks for any help.Jeff
BN44-00514A Repair - Page 1
Forum section: electronics / repair

author: FoxMulder
author_rank: Newbie
timestamp: November 04, 2019, 05:05:29 am
content: Hey guys,So I have a Samsung PS60E8000 that died. The bridge rectifier, main fuse and 1 of the power factor correction MOSFETs had shorted. I replaced all those and the set was working ok. Then again it failed. This time one of the FETs that powers Vs and Va had given up. I replaced both these FETs and the set still wont work. All the capacitors look ok.Pulling the PSU out of the set, and applying mains power has the PSU click the relay on. This implies something is driving PS_ON low.I get all the correct voltages STBY, D5.3V, 15V, but not Vs and Va. Wiring a 300 ohm resistor to link VS_ON and V_5.3 doesn't do anything.I tried to work out what was driving PS_ON low on startup so I traced it out. Measuring PS_ON I was getting 1.6V. I traced this to the voltage divider formed by RQ890 (2.4k) and RQ825 (1k).In order for PS_ON to be 1.6V it would mean that Pin 4 of UQ802 must be 0v. (5.3*1000/(1000+2400)) ~ 1.55VI removed RQ890, RQ825 and CQ817 and I measured 3 Ohms to ground on Pin 4 of UQ802. I'm assuming UQ802 is stuffed, however it looks to be some sort of micro-controller and thus I would need the firmware to reprogram a new one.Anyone have any luck replacing UQ802? Or any schematics for this board? I might be better off binning the TVas a new PSU is around $200.Thanks,Asela

author: FoxMulder
author_rank: Newbie
timestamp: January 05, 2020, 09:14:59 am
content: If anyone else is curious, I managed to find someone with a board and they posted it to me. Sure enough Pin 4 of UQ802 on the new board is at high impedance when off. New board is currently operating in the TV. UQ802 is a microcontroller with Samsung code on it, but no one else has the code. If it fails, Samsung will only sell the board (which is of course no longer produced) not the component. It would be possible to rig up a PIC or other micro to perform the same function if it ever fails again, however part of me thinks the effort required to do so, might as well just buy a new TV.

author: Hornnumb2
author_rank: Regular Contributor
timestamp: January 07, 2020, 03:31:13 am
content: Did you look on shopjimmy for a repair kit.

author: TheN00b
author_rank: Contributor
timestamp: January 07, 2020, 05:10:53 am
content: A repair kit probably won't have this sort of thing in it. OP, have you desoldered it and checked the bottom of the chip? Sometimes important info can be silkscreened onto the bottom. If not, then you may want to scrape off the top plastic of the chip VERY CAREFULLY to see if there is any writing.
Bn44-00516a samusung power board - Page 1
Forum section: electronics / repair

author: ant17
author_rank: Regular Contributor
timestamp: June 03, 2020, 11:54:23 pm
content: hi i have ps64e8000gm plasma television.my brother tells me that when they were watching it just went black. So i said would have a look at it for him. when i opened it up i thought the first thing to look at was the power supply which was bn44-00516a switchmode power supply. i tested it and when i first tried to power it up it blew the 20 amp breaker. which i thought must of been a major short circuit somewhere in the power supply. my first thought was to get out multimeter and check all the main transistors for dead shorts. i found 3 completely shorted transistors and a defective ice3br2565jf offline switch mode ic. so i replaced them and short was gone but the high voltage side seem to be present. when i checked the low voltage side after the 2 main power / isolation transformers there was no stand by voltage and none of the other low voltages were present on that side. it was completley dead on the low voltage side so again i checked the voltages on the main switchmode ic found that between ground pin and vs pin of the ic should be 25volts but only voltage present was on the drain pin 360vdc and some of the pins seem to have 30ohm short to ground but with out the schematic i am really having trouble visualizing the circuit can any tell me where i might get a schematic for the bn44-00516a even if i have to pay for it if somone could help i would be greatful
bn44-0073c power supply (dead) - Page 1
Forum section: electronics / repair

author: phildecor
author_rank: Newbie
timestamp: November 02, 2020, 01:27:06 pm
content: help plz ,,,,bn44-00773c dead no 5v no 12v

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 02, 2020, 02:13:48 pm
content: https://www.tvpartstoday.com/BN44-00773C-Samsung-TV-Module-power-supply-p/bn44-00773c.htm

author: phildecor
author_rank: Newbie
timestamp: November 02, 2020, 04:35:15 pm
content: looking for schematic to fix ,,,thanks

author: KevinA
author_rank: Regular Contributor
timestamp: November 02, 2020, 09:55:35 pm
content: Unless someone has sat and drawn this out, I doubt it exists.Even if you found a schematic, parts are close to unobtanium unless you have an account with a company like ASWO.Kevin

author: amyk
author_rank: Super Contributor
timestamp: November 03, 2020, 04:26:09 am
content: Schematic? Make one yourself, these are pretty standard SMPS with not that much complexity.
BNC 625A SmartARB service manual - Page 1
Forum section: electronics / repair

author: markkkk42
author_rank: Newbie
timestamp: September 16, 2020, 03:11:08 am
content: I have a BNC 625A function generator and its proven to be a great bit of kit. The power supply has decided to give up the ghost. Does anyone have any schematics for service manual for this unit please?...or is it just a + and - 15V powersupply

author: rvalente
author_rank: Frequent Contributor
timestamp: September 16, 2020, 03:34:50 pm
content: I've never heard about this brand but, just stating the obvious... Did you try to contact the manufacturer?
[Solved] Board U11150 Acova Timerprog repair - Page 1
Forum section: electronics / repair

author: ghorizo
author_rank: Contributor
timestamp: January 15, 2020, 06:54:42 pm
content: Hello I wanted to try and repair this little control board from the bathroom heater.When powered it gives no signs of life: leds are off and so is the relay. The main resistance measured 62 ohms.I can see no visibly damaged components for which I hope for as that is about my level. I have tried following the live circuit but get lost quite quickly and don't feel so confident about doing, but still I would really like to understand the diagnosis process as I'm constantly around broken electronics.Could someone please help me go through this?

author: fzabkar
author_rank: Super Contributor
timestamp: January 16, 2020, 02:22:00 am
content: I would start by desoldering and reflowing each of the corroded solder joints (there are many).Then I would measure the voltage across each of the capacitors. One will probably be the coil voltage for the relay, while the other will probably be the Vcc voltage for the NEC microcontroller IC.Be very careful. You are working with a live circuit.

author: ghorizo
author_rank: Contributor
timestamp: January 16, 2020, 08:29:07 am
content: So I have re-soldered all the trough hole joints and the more accessible smds.Measured voltae across the electrolytic caps is 3.10 and 3.15 volts dc. On the film one I get varying measurements in the mV range, could it be it the culprit? But when removed from the circuit it measures up to spec so maybe no.Update:So after that all the components measured seemed fine I thought of looking for the installation manual from the manufactgurer's website.Turns out whoever got into this before me swapped some wires around so it was installed wrong (lucky the owner was convinced it was working before!). What I marked as earth and had quite a few suspicions about turns out to be neutral, and there is no earth but a control wire to remotely control the unit.So here it ends quite stupidly from not reading ahead, hey at least I cleaned up the corroded joints.Thanks anyway fzabkar I appreciate the help!
Boombox only works on one speaker with 2/3 inputs - Page 1
Forum section: electronics / repair

author: optonox
author_rank: Newbie
timestamp: July 06, 2020, 10:35:01 pm
content: Hi,I have this boom box.It has three modes:- Tape- TV- RadioTape works with left and right channels but the TV and RADIO modes only have audio coming out of one of the two channels (I have swapped the speakers just to be completely sure).The speakers have a 1/4" mono type plug.Does anybody know why this would only be working in 2/3 modes or how I could go about debugging this?Thanks

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 07, 2020, 12:50:48 am
content: Bad contacts in function selector switch?
Boonton 72BD Repair - Page 1
Forum section: electronics / repair

author: Kjo
author_rank: Regular Contributor
timestamp: April 25, 2023, 04:03:28 pm
content: I have had two of these Boonton meters for as long as I can remember. They are basically the same with one having a digital meter and the other an analog meter. (I sold the analog 72B some time ago to clear up some bench space.) I hadn’t used it for quite some time because the auto range was flakey and the meter would not remain stable at zero. But I always had something els to do instead of digging into the 72BD.But a recent bench cleaning and clearing brought the 72BD front and center to where I couldn’t ignore it. Now my unit is a rather early version with a serial of 1937. Based on the date code on some parts, I would say the manufacturing date was 1979-1980. I have a manual from much later production (1987), but it appeared to be nearly identical. I was hopeful that the design hadn’t been changed too much in the intervening time.As usual with electronics, one needs to check the power supplies first, as without them operating little hope is there that other parts will function properly. The meter has 3 primary supplies based on traditional transformers and linear IC regulators. (+-15VDC & 5VDC.) A quick check indicated 4.4V on the 5V bus, 15V on the +15 bus and -21V on the -15V bus. Clearly 2 of the 3 are a problem.I next looked at the raw DC input busses to evaluate the condition of the main filter capacitors. The 5V supply was around 7V, really too low for the headroom required by a LM7805. So this input cap was likely very leaky and overloading the transformer winding.The -15V input bus should be in the -25 to -28VDC range, but had more than 8VAC and unstable DC voltage. This cap likely had a high internal impedance, and the associated LM7805/LM723 were likely faulty. I removed all the capacitors, and all were faulty; the large caps had degassed and eroded dome of the PCB trace tin & copper. ESRs of a couple hundred ohms and leakage of 400K says it all.Interestingly, the large cap values were marked with 10% of the values specified in the newer manual. (250uF/2200uF & 1000uF/4700uF). A look at the photo of the replacement caps indicated that there is not a lot of headroom under the transformer. Maybe Boonton couldn’t get caps to fit in higher capacity in 1979. My 21st century caps are small enough to use the newer spec size!You can see the cap repair in the back side PCB photo where the eroded traces are repaired. On applying power, all three supplies were well within spec after the required adjustments were made. The range switches all work properly and the 2pf range will zero out and remain stable.Next I will be checking some of the performance specifications, but I do not have capacitor standards to do a good calibration at this time…..
Boonton 9200C & 91-12F probe help? - Page 1
Forum section: electronics / repair

author: wd5jfr
author_rank: Regular Contributor
timestamp: July 05, 2024, 06:56:20 pm
content: Bought the meter w/o a probe at Hamfest earlier this year and found a probe on QTH that might work but I can't find a 9200C manual, only a 9200B. I know the meter has to be matched to the probe but I'm going to try to see if I can set it up so I can get readings within 5% or so. So far, I have not had much luck since I don't know if the 9200B manual Preliminary Checkout or Set Up is valid for the 9300B. I checked the probe diodes in series and got 0.6045 VDC on my Fluke 189II so I assume the probe is probably OK. I also assume the meter has to be set for whatever that will make read if that's possible. With the CPU and many options I'm at a loss. Any help with the manual or setup or how I might be able to get it working appreciatedThanksHank

author: George Edmonds
author_rank: Frequent Contributor
timestamp: July 05, 2024, 08:44:54 pm
content: HiIn my experience all Boonton meters are no more than low voltage dc meters with computer scaling.I do have a PDF on Bootom probes but it is too large to postG Edmonds

author: wd5jfr
author_rank: Regular Contributor
timestamp: July 05, 2024, 10:57:40 pm
content: Hey GeorgeCan you email the Bonton probe PDF to kolesnik@sbcglobal.net?ThanksHank

author: George Edmonds
author_rank: Frequent Contributor
timestamp: July 06, 2024, 12:24:02 am
content: Hi HankEmail sent to you.G Edmonds
Boonton 92C repair question - Page 1
Forum section: electronics / repair

author: WB8PFZ
author_rank: Regular Contributor
timestamp: February 26, 2024, 04:02:20 pm
content: I have a module 92 rf microvolt meter that has an issue. Everything appears to work but all the readings are 5.5 db high. I am using a Hp signal generator for my rf source, double checking it with a HP spectrum analyzer. Any thoughts. Thanks Mike

author: TimFox
author_rank: Super Contributor
timestamp: February 26, 2024, 04:23:30 pm
content: That’s consistent with a generator calibrated for voltage into a 50 ohm (external) load, but a meter with an input impedance much larger than 50 ohms.I have two similar Boonton units: one is a power meter, where the probe shows 50 ohms to the source, and the other is a voltmeter with high input impedance, supplied with a removable 50 ohm termination.Ideally, a very high input impedance results in an indication 6 dB high (x2 voltage).

author: WB8PFZ
author_rank: Regular Contributor
timestamp: February 26, 2024, 09:43:58 pm
content: Well putting a 6 db attenuator between the rf out of the generator and the rf probe put all the scales in line with where they should be.

author: TimFox
author_rank: Super Contributor
timestamp: February 26, 2024, 10:29:15 pm
content: Try adding a 50 ohm termination between the generator and the Boonton probe input.Note that your spectrum analyzer has a 50 ohm input impedance, but voltmeters rarely do.

author: WB8PFZ
author_rank: Regular Contributor
timestamp: February 27, 2024, 01:19:51 pm
content: I used a t connector in between the sig. gen and meter with a 50 ohm load and it now reads correctly. Thanks for your insight. Mike
Boot issue? Wandel & Goltermann PSM-39 Selective Level Measurement Set - Page 1
Forum section: electronics / repair

author: youngplayer
author_rank: Newbie
timestamp: July 14, 2020, 03:36:25 pm
content: I've recently obtained a PSM-39, however, it does not seem to work.When I turned it on for the very first time, it said "main memory corrupted, using default settings", or something along these lines. I also remember it displaying a dBm number (like it should). However, on subsequent boots, all I get is this.https://www.youtube.com/watch?v=l7dU29ve7fU&feature=youtu.beI'm guessing the beeps are similar to the BIOS beeps, and there's a specific error tied to that beeping pattern.I have popped the top cover off, inside is this seven segment display, which displays the parts of the boot process that pass (I think anyways). There's also a lithium battery (3.5V, 750mAh) inside, that one is really dead (about 0.1V @ 10MOhms). The whole memory corruption thing and an empty battery makes me assume that that battery was for holding user settings in volatile memory in between boots. However, that would not explain why it won't display the correct stuff after boot. I have also hooked up a current limited PSU to the battery terminals with 3.5V, just to see if that does anything. And it doesn't - it draws about 175uA, be the device on or not, so it's probably flowing into the battery - I have not tested this for longer than about 10s.tl;dr:Does somebody have experience repairing similar devices or "memory corrupted" issues?PS: Does somebody have any kind of document on this device or it's sister models? I have searched the depths of the internet, and the only thing I found was this datasheethttp://www.testequipmenthq.com/datasheets/WANDEL%20&%20GOLTERMANN-PSM37-Datasheet.pdf, but I need a service manual or operation manual.
Boot problem Agilent E4417A EPM-P Series Power Meter. - Page 1
Forum section: electronics / repair

author: magnetchief
author_rank: Contributor
timestamp: November 21, 2022, 04:00:17 pm
content: Hi, I'm having an issue with an Agilent RF Power meter.Until recently it was working perfectly.When connected to the mains outlet the Power led is illuminated but pushing the button has no effect.The instrument will not boot up.Weird thing. If I unplug the instrument and hold my finger on the power button, plug in the power cord it will boot up correctly.I have checked all the various fuses, there are a pair on the mains power connector and one inside the case on the power board.I did notice a 3V Lithium battery soldered onto what looks like the main processor board. This battery measured 0.9v without the power cord plugged in and 2V with the instrument turned on.Any help appreciated, i'm thinking that the 3v battery at least needs replacing.

author: R-1125F
author_rank: Regular Contributor
timestamp: November 21, 2022, 04:50:06 pm
content: The battery does need to be replaced, but I don't think that is the problem. I have fixed a few of these and the main problem is the membrane keypad FPC. Replacements are available from China and they are really cheap. However, they are a pain to replace. Another thing about the Chinese replacement part is that the standby LED is red instead of orange.

author: R-1125F
author_rank: Regular Contributor
timestamp: November 21, 2022, 06:07:53 pm
content: I should add, change the battery first (it needs it anyway). If it fixes the problem please post here.

author: magnetchief
author_rank: Contributor
timestamp: November 21, 2022, 07:02:23 pm
content: Will do, thanks for the advice.Wow, they are cheap. $22

author: nfmax
author_rank: Super Contributor
timestamp: November 21, 2022, 07:09:31 pm
content: I had a very similar problem with my EP4418B power meter, diagnosed & fixed here:https://www.eevblog.com/forum/repair/(mended)-ep4418b-power-meter-doesnt-turn-on/msg3991700/#msg3991700It might not be exactly the same fault, but it may help you

author: magnetchief
author_rank: Contributor
timestamp: November 28, 2022, 06:57:43 pm
content: All sorted,Replacement battery fixed the issue.Also noticed that there is a pre boot check for the lithium battery. It passed.

author: R-1125F
author_rank: Regular Contributor
timestamp: November 28, 2022, 07:47:53 pm
content: Good to know that fixed the problem. Let us know if it fails again.

author: magnetchief
author_rank: Contributor
timestamp: August 24, 2023, 07:29:39 pm
content: Hi, of course here we are a year later and it's failed again.The 3v battery was reading 2v, so swapped it out, again.This time no luck. I'm thinking of trying the membrane keypad repair.
Bootlooping Thinkpad X230i - No backlight - No image (schematics included) - Page 1
Forum section: electronics / repair

author: Romanizer
author_rank: Newbie
timestamp: June 07, 2019, 03:01:28 pm
content: Hello fellow Engineers and hobbyists,A couple of days ago, I got a broken Thinkpad X230i from a friend, saying it was unfixable and he saved it from recycling.Here is the problem:When turning it on, it stays on for about 5 seconds and then turns off again. This repeats indefinitely and happened when battery and/or charger(20V Bench PSU) powered. While bootlooping, it shows no image on screen and the backlight is off, but The Keyboard light and the thinklight are both on.I checked all rails: 20V DC-in, 5V, 3.3V. All are present. The only rail I could make out that is missing is the VCC_GFXCORE_I rail for the CPU's integrated GPU. I'm guessing its an i3-3310M.The VCC_GFXCORE_I rail is provided by a VT1324SFCX, which in turn is controlled by a VT1318MFQX (schematics attached, see pages 79 & 80).I tried injecting Voltage into the rail, to see if there were shorted caps, because my meter was measuring about 1.4 ohms. But no luck.I noticed that the power management IC VT1318MFQX is sending a fault signal to the buck converter VT1324SFCX telling it to shutdown.Does anyone have an idea to what is wrong with my newly acquired Thinkpad?Any help is greatly appreciated!!

author: Rasz
author_rank: Super Contributor
timestamp: June 08, 2019, 06:22:06 am
content: lack of VCC_GFXCORE can be faulty bios, bad ram, etc, GPU is brought up late in boot processbut 1 ohm on gpu-vcore is too low, take off L29 and check which side is low resistanceor buy <$20 replacement motherboardhttps://allegro.pl/oferta/plyta-glowna-lenovo-thinkpad-x230-core-i3-8079804809https://allegro.pl/oferta/100-sprawna-plyta-glowna-lenovo-x230-gw-fv-7994395139https://allegro.pl/oferta/plyta-glowna-i5-3320m-lenovo-x230-2325-8017430419even $10 with fan controller defecthttps://allegro.pl/oferta/plyta-glowna-lenovo-x230-3320m-intel-slj8a-8118683212personally I LOVE x220/x230 motherboards for small projects(home routers,nas,camera servers etc), they cost less than raspberry pee while delivering x10 the performance and IO. I usually buy ones with defects like one USB port blown for $5-10 including lower case (means comes with radiator/fan and often wifi/bt)

author: Romanizer
author_rank: Newbie
timestamp: June 08, 2019, 01:44:46 pm
content: Thank you for your response!I was guessing that the GPU might not come up after a couple of seconds after boot, but my scope was confirming that the VCC_GFXCORE was trying to turn on.I can rule out bad ram, because I tested multiple sticks in various configurations. I'll take of L29 and try locating the short then.I'll order a 'new' mainboard as a last resort, first I will see if i can fix it very cheap. If not the mainboard are super cheap aswell, i did not expect that.
BORRI 30kVA B8033fxs Uninterruptible power supply precharge relay fault - Page 1
Forum section: electronics / repair

author: SmartFoxElectronics
author_rank: Newbie
timestamp: June 15, 2020, 02:07:05 pm
content: Hi guys,This is my first post, I thought I'd create an account here since I've started a new job and have far more time & freedom to investigate faults on the units I'm repairing, however, I've come from a job that dealt primarily in logic level electronics, to a job that builds, tests and repairs 3 phase industrial power supplies & have only been in the electrical field as a whole for 5 years so am by no means a veteran...Anyways, I'm having a recurring issue on the charger/inverter modules of BORRI B8033fxs UPSs, on certain batches I get in, usually around one out of the 3 modules fails when I run them up through the test software it fails, giving me the fault code "042 precharge relay fault"I've traced the control circuit itself to a couple of ICs on the far right corner of the PCB, but changing these does nothing, and for the most part the signals match up to those of a working unit.Other things I have tried:Changing rectifier and inverter IGBTsChaning the thyristorsChanging DC BUS capacitorsThis fault used to only occur in units that had been exposed to the elements & had seen corrosion but now seem to be getting more and more units that look relatively new giving us the dreaded precharge fault. It's a common fault that nobody else has been able to nail down, I'd really like to get to the bottom of it so I can stand out a bit to the bosses!Any help would be much appreciated!

author: trobbins
author_rank: Frequent Contributor
timestamp: June 16, 2020, 12:16:51 am
content: Have you identified if the fault code relates to a specific digital input, or an analog trip level, or ...?Have you identified the precharge relay that would be the subject of the fault code? Is it just being controlled by a coil enegisation signal, or is their a state contact being fed back or an analog signal being fedback that would be directly related to the precharge function performing ok (ie. the capacitor being precharged reaches a set level within a certain time)?
Bosch 144-8CH15-L E Bike Charger no Power on LED no Output - Page 1
Forum section: electronics / repair

author: vanillaboard
author_rank: Newbie
timestamp: September 20, 2024, 10:05:02 pm
content: Hi everyone,A colleague gave me his eBike charger to check out, as it's no longer working.Upon opening the charger, I immediately noticed that a smaller component between the electrolytic capacitors had burnt out. I assume it was a capacitor?I removed the damaged component completely and temporarily bridged the burned fuse after the 230V input on the board.Unfortunately, the charger is still not functioning. The two large 200V 470µF capacitors are now charged to around 155V, which wasn't the case before my intervention. The fuse is also holding up fine.I also checked the smaller control board where the Slow/Fast button is connected, and I've marked the voltage readings on the picture of the main board. Since all the voltages seem to be present, I'm at a bit of a loss as to what the problem could be.On the Power on LED i have about 1,7VNo hot Components on the smaller controller board.My colleague mentioned that the green LED should light up as soon as the device is plugged in, but that's not happening.Any ideas on what the issue might be? Does anyone here have experience with these types of chargers?Thanks a lot for any help!
Bosch al1130cv not charging - Page 1
Forum section: electronics / repair

author: MirtSergiu
author_rank: Newbie
timestamp: March 19, 2020, 05:19:59 pm
content: I have this bosch al 1130cv 10.8v battery charger. It worked fine until one day when it stopped charging. When i insert a battery, it's charging for 3-4 seconds then the relay closes and it shows the constant green light and when i measure the battery voltage, it shows 8.7v. I took a look inside and i couldnt see anything that doesnt look ok. What could it be?
Bosch Athlet battery pack rebuild - Page 1
Forum section: electronics / repair

author: justaguy
author_rank: Contributor
timestamp: February 14, 2022, 04:14:59 pm
content: I'm fighting with the battery pack of a Bosch Athlet BCH 6ATH18 vacuum cleaner.Device did not take charge. Upon inspection, one of the 5 Li-Ion cells was showing only about 0.5V. I have bought new cells and rebuilt the pack, however it still refuses to charge. There are a BQ77PL900 battery manager and an atmega328 running the show. The charge mosfet appears to be ok and if I connect the pack keeping the uP under reset (which should let the BQ77 run in stand-alone mode) the batteries get charged. Therefore I assume that the uP has stored the battery failure in eeprom and got in some lockdown/brick mode.My only hope seems to be to reflash the uP, does anybody have the right firmware?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 14, 2022, 04:23:25 pm
content: Have you seen this thread?https://www.eevblog.com/forum/reviews/dyson-v7-trigger-cordless-vacuum-teardown-of-battery-pack/?allIt looks like manufacturers really don't want you to repair their battery packs, since they essentially self destruct if you are not careful - like a time bomb!It may be possible to buy a replacement battery module on AliExpress that works on this model?

author: abdulbadii
author_rank: Frequent Contributor
timestamp: February 15, 2022, 12:34:01 am
content: pass BMS by ?try put its schematic/picture on

author: amyk
author_rank: Super Contributor
timestamp: February 15, 2022, 03:42:16 am
content: RE the communication protocol between the battery and device which uses it, write your own firmware or emulate it... might be easier to always report 100% than an actual battery gauge.

author: justaguy
author_rank: Contributor
timestamp: February 15, 2022, 09:20:27 am
content: I'm under time pressure from my wifeI think I will just buy a new vacuum cleaner.It's just a shame that those things are not meant to be repaired; I can understand the manufacturer's concerns about safety when dealing with Li-Ion, but sometimes it smells of planned obsolescence...
Bosch BHN20L/04 vacuum red light issue - Page 1
Forum section: electronics / repair

author: m4ss4
author_rank: Newbie
timestamp: September 22, 2024, 08:56:32 am
content: I'm new here and I would like to bring the life back to this vacuum cleaner.The problem: When it gets power the led showing red and after 10 seconds it goes out. Manual says it's the 5S battery pack thermal sensor signal. I've measured the thyristor and it's 10k Ohm and on heat the resistance is dropping. Probably it's OK.When the PCB attached to power the motor is not turning on, but directly from the battery it works. Motor seems OK.I did a couple of measurements, but I'm not sure what I see.More details: Mp/Mg=motor positive/motor ground Bp/Bg=battery positive/battery ground Cg=charger groundVoltagesBP-BG 18.7VMP-MG 0VBG-MP 18.7VCG-MP 18.7VBG-MG 3.43VContinuityBP-MP yesBG-CG yesBG-MG noWhen I got the device and turned on there was this stucked red light issue. That's why I take apart, but one time while testing unfortunately connected the battery wrong direction and a couple of parts got burnt. Those parts I've replaced(Schottky diode, 1 resistor) So the original problem it still present.If you need more image or infos I will provide. Thank you for your help!
BOSCH Drill Charger Bc330 4V-21V - resistor value? - Page 1
Forum section: electronics / repair

author: Spare647
author_rank: Newbie
timestamp: October 20, 2020, 09:55:20 pm
content: Hi guys I had plugged in my drill charger and it popped and started to smoke. After opening it up I had seen that one of the resistors had exploded, I don't know why. If anybody has a similar model and can let me know the resistor value the blown resistor is, that would be greatly appreciated. I live in North America btwThe blown resistor is in between the capacitor and transistor with the metal plate.
Bosch Exhaust-gas analyser ETT 008.55 (need schematic) - Page 1
Forum section: electronics / repair

author: Henk4free
author_rank: Newbie
timestamp: May 01, 2023, 12:21:46 pm
content: I am looking for a schematic of a Bosch ETT 008.55.it's about the main board, which is what i'm looking for.damage has been caused by a leaking battery