hybridfree/eevblog-posts huggingface dataset:
MARCONI 6200 repair - Page 1
Forum section: electronics / repair

author: Avinoam
author_rank: Newbie
timestamp: February 08, 2020, 09:55:51 pm
content: תמונה.pdf(110.57 kB - downloaded 181 times.)תמונה.pdf(110.57 kB - downloaded 181 times.)Hi ,I need to change the set-up for my MARCONI 6200 , for change of output attenuator .To get into set-up screen , I need the Primary password .Can you help ? any idea ?Thank you ,Avinoam\תמונה.pdf(110.57 kB - downloaded 181 times.)

author: George Edmonds
author_rank: Frequent Contributor
timestamp: February 08, 2020, 11:19:03 pm
content: HiFirst try 123456 or however number of digits it will take.There is a super user password that is derived from the instrument serial number. First make sure that the printed serial number is the same as the one displayed on the screen (ESN).Post the details and I will try to obtain the super user password for you.

author: Avinoam
author_rank: Newbie
timestamp: February 09, 2020, 04:53:03 pm
content: Hi,I tried 123456 , 111111 ,222222 , ............The code length is 100000 - 999999 , by the manual .The serial number on the factory plate is : 236261/018 .The serial number in Build State , on screen is : 123456/123 .Can this data help ?

author: Manul
author_rank: Super Contributor
timestamp: February 10, 2020, 02:08:16 am
content: I'm not familiar with this model, but if nothing else gives result, there is two overkill ideas.1. If password is changable, it should be in eeprom somewhere, so dump it and look. If it is fixed, maybe disassemble / reverse the firmware.2. Simulate keyboard presses with external MCU and brute force.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: February 10, 2020, 02:53:41 am
content: HiThe super user password is not held in the EEPROM, a number of people have looked for it, the level two password is held in the EEPROM. Best guess is that it is generated from the instrument ESN by an unknown algorithm which is part of the instrument firmware.Not certain what is going on here, the factory plate serial number and the displayed ESN should be the same.George.

author: comtek
author_rank: Newbie
timestamp: July 28, 2020, 03:56:30 pm
content: HiThe Level 1 password is 9999 and the Level 2 password is 999999 (normal default from factory).
Marconi 6200B. service manual - Page 1
Forum section: electronics / repair

author: Johnny10
author_rank: Frequent Contributor
timestamp: March 03, 2023, 09:11:27 pm
content: Looking for a Marconi 6200B Service Manual.I am buying a parts/repair unit next week.Thanks

author: George Edmonds
author_rank: Frequent Contributor
timestamp: March 03, 2023, 11:30:48 pm
content: HiThere is very little information on the Marconi 62XX series available.I do have a copy of the 6200A service manual, BUT it is over 300MB in size and I am not certain of the Copyright status so am reluctant to put a copy on the internet.May I suggest that you join the Marconi-Test-Instruments@groups.io there is one member who probably knows more about the 62XX series than most/anyoneG Edmonds

author: chick0n
author_rank: Regular Contributor
timestamp: November 14, 2023, 12:39:14 pm
content: I have a copy of the 6200B Service Manual, but without Schematics. I think its available on xdevs Server...yep...https://xdevs.com/doc/Marconi/6200B/Marconi_6200B_Service_Manual_OCR.pdfI own a 6203, so a complete Service Manual for 6200 or 6200A would be nice to have. I already asked in Marconi Group...I think, there where 3 "iterations", of the 620x Series.620x - has CRT Display and VCXO Osc.620xA - is like 6200, but has LCD Display and OCXO Osc.620xB - has the "A" Stuff + Floppy Drive and you can use detectors with EEPROM Correction. Also the Digital Part is maybe new / more modern. (You can Update Firmware with Floppy now, instead of changing EPROMs.)If im correct...

author: chick0n
author_rank: Regular Contributor
timestamp: September 06, 2024, 08:37:22 am
content: We have the Full Service Manuals with schematics for the 6200 and 6200B Series now. I Uploaded them to xdevs server, and ko4bb.Also the Passwords for 6200:lvl1: 9999lvl2: 999999primary: 456444marconi: 150357

author: Ice-Tea
author_rank: Super Contributor
timestamp: September 06, 2024, 08:42:15 am
content: Absolutely fantastic! Much appreciated!
Marconi/Aeroflex screen repair - Can you diagnose this? - Page 1
Forum section: electronics / repair

author: homem_do_saco
author_rank: Contributor
timestamp: August 26, 2020, 02:31:01 pm
content: Hi everyone.I recently acquired a Marconi 2030 signal generator. It came with a defective LCD screen that does not impair usage, but is annoying.However, I don`t think the LCD screen itself is at fault, because the LCD self test flips the pixels. I think it`s some logic chip`s problem.If someone could take a look at the schematics and come up with some idea, that would be appreciated.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: August 26, 2020, 06:09:47 pm
content: HiThis is 99.99% certain to be a faulty LCD screen which must be replaced to clear the fault.George G6HIG UK

author: Gyro
author_rank: Super Contributor
timestamp: August 26, 2020, 08:12:50 pm
content: Can you take a better lit photo? The detail of the screen is mostly obscured by the reflection of you and your shirt.Are you talking about the black streak above the -144dB in the first photo?Edit: Ah, I get it - the horizontal line across the middle of the screen (At first look, I thought it was a separator).

author: George Edmonds
author_rank: Frequent Contributor
timestamp: August 26, 2020, 11:32:29 pm
content: Just to clarify the situation.ALL of the display decode and LCD driver logic is embedded in the display itself.There were two different LCD displays used by Marconi in the 203x and 204x range. the original one was manufactured by Epson and is totally unobtainable now, the later display was manufactured by NAN-YA and a small number are still available. The CCFL driver is different between the two displays and MUST be changed with the display.George G6HIG Dover UK
Marconi/Ifr 2967 - Page 1
Forum section: electronics / repair

author: ct1bxt
author_rank: Contributor
timestamp: December 11, 2022, 07:26:28 pm
content: Hello,does anyone as a Marconi/Ifr 296X, preferential a 2967, witch I can compare some spectrum analyser screen´s ?RegardsRodrigoct1bxt
Mark Levinson № 27.5 power supply schematic neede. - Page 1
Forum section: electronics / repair

author: FriedMule
author_rank: Frequent Contributor
timestamp: May 06, 2022, 03:54:57 pm
content: I have found schematic on everything in the Mark Levinson № 27.5 power amplifier except for the power supply, does any of you have something? A drawing, your own or professional schematic?Deeply thanks in advance
Marking code 204 and SHM at Agilent E5601B  - Page 1
Forum section: electronics / repair

author: Linh Le
author_rank: Newbie
timestamp: March 21, 2023, 05:34:36 pm
content: Hi guysI am repairing E5061B network analyzer. But I can't find the part number of the two components with the marking code 204 and the SHM at the RF port of the receiver board. If you know can you help me please
markings on thermal switches in GE microwave oven - Page 1
Forum section: electronics / repair

author: MrWO
author_rank: Newbie
timestamp: February 11, 2021, 03:32:14 pm
content: I am having difficulty understanding the makings on a thermal switch I removed from a GE microwave oven. The markings on the back NT101 and KIE-on the face:V 40706320

author: CaptDon
author_rank: Super Contributor
timestamp: February 11, 2021, 07:40:10 pm
content: Don't know that one specifically. GE used two thermal protectors. One was on the side of the magnetron tube and was a self resetting device, round with two 1/4" spade lugs. The other was on top of the cooking cavity and is NON-RESETTING and most appliance repair parts stores won't sell you one or even sell you an equivalent. It is considered a 'safety' issue assuming if your old one tripped it was from a cooking fire and there may be hidden damage. They are both normally closed and in most cases carry the full load current of the oven so that when they trip the thing goes totally dead!! Don't jump them out, if you get a real thermal issue in the future the oven won't shut down and may cause a kitchen fire. If you can't find a replacement at a parts store check with an 'appliance repair guy' as they may have something pulled from a used oven with a bad maggie or transformer. I may even still have some laying in a box of microwave parts. Some of the non-resetting switches on top of the cavity can be taken apart and reset. There is a 'clicker' bi-metal strip which is meant to hold a tiny microswitch device in the closed position. When the metal strip heats it pops to an inverted arch shape and releases the tiny switch. You can reset the metal strip and re-assemble the switch. You have to bend little metal tabs to take the switch apart.

author: fzabkar
author_rank: Super Contributor
timestamp: February 11, 2021, 07:59:17 pm
content: Could it be a resettable switch that opens at 70C and closes at 40C?

author: MrWO
author_rank: Newbie
timestamp: February 12, 2021, 08:50:50 pm
content: That was helpful
Marshall Bass State B65 & Raven Student 10 service manuals wanted - Page 1
Forum section: electronics / repair

author: cowasaki
author_rank: Frequent Contributor
timestamp: September 01, 2019, 12:26:54 pm
content: Anyone know where I can get hold of service manuals for the above, especially the MarshallThanks in advance.

author: cowasaki
author_rank: Frequent Contributor
timestamp: September 02, 2019, 07:26:02 pm
content: Just had a reply from Marshall with the schematic. They will happily send them out to people!

author: 2N3055
author_rank: Super Contributor
timestamp: September 02, 2019, 08:11:27 pm
content: That is great news!!If you a repairing B65 please share what it was...Maybe a quick post?Regards,

author: cowasaki
author_rank: Frequent Contributor
timestamp: September 02, 2019, 08:43:02 pm
content: Quote from: 2N3055 on September 02, 2019, 08:11:27 pmI will. I'm looking forward to having a mess with it. He's bringing them both in tomorrow.

author: cowasaki
author_rank: Frequent Contributor
timestamp: September 03, 2019, 08:39:54 pm
content: I have some photos but got the amp home today. There are five screws which go through the lid into the amplifier itself and once removed the back has to be removed as well in order to gain access to the rear of the speaker. You need to remove the speaker wires and the gunk which stops the wires rattling about. Once that's done the amplifier electrics slide out backwards.With the amp on the bench I measured the speaker's impedance and found it to be 6 ohms so selected a 6 ohm speaker for testing. I hooked it up and the power light came on but no output. I then prodded about inside with a plastic chop stick to see if anything obvious was loose. The large white rectangular resistors are a favourite due to their weight. The next step was to photograph the inside and make a note of where all the wires go before disconnecting the cables and removing both boards.Looking at the back of the board it became apparent that there were a LOT of poor solder connections. The places that are normally an issue are the sockets and pots. I re-soldered all these and was still having problems. Looking through the microscope I found that one of the tracks to the volume pot had broken and so mended this using some solid core copper wire. So with that fixed it worked and I re-assembled it to find it not working again!Next I realised that all the faders were also loose so removed that board and re-soldered all the bad connections there too.Re-assembling it again it stopped working again when I screwed the plastic socket retainer in place. Taking it apart again I realised that all the sliders and sockets were oxidised so cleaned them all and the faders with dioxit.Now it all fully works.....These Marshall amps are more often not working due to bad connections than component failure.
Mastech 9803R Repair Help - Page 1
Forum section: electronics / repair

author: larrybud
author_rank: Contributor
timestamp: March 29, 2024, 12:30:26 am
content: I purchased a Mastech 9803R benchtop meter off ebay for "parts or repair" and everything works on it except two odd issues, which I suspect are related:Capacitance reads half the expected valueThe voltage drop when testing a diode is twice the expected valueI opened the unit up, checked for the common culprits (bulging caps, cooked resistors, cold solder joints) but didn't notice anything.First, does anybody happened to have a schematic of this thing, and if not, any advice on what to look for?Also, this uses the NJU9210 chipset. I found the datasheet for that and adjusted the 1v reference pot, and the DC/AC. While I don't have a super accurate reference voltage, I'd say I'm close enough where the diode drop and capacitance values should be within a few percent. Starting to wonder if the chip is faulty.

author: sean0118
author_rank: Frequent Contributor
timestamp: March 29, 2024, 09:10:25 am
content: Have you checked that the DC volt mode works on all ranges? Could be one of the relays / reed switches or resistor network has died?I suspect you're right and the two issues are related. If it's charging the capacitor with a fixed current and has a false reading of double the voltage the capacitance will be half expected. I = C(dV/dt)

author: MathWizard
author_rank: Super Contributor
timestamp: March 29, 2024, 09:50:26 am
content: If you have the time, I'd try and find the sections on the DMM, the parts and pins associated with the diode/cap mode. I would do it in something like LTSpice, and then it's easy to see to sometimes if removing 1 resistor or other part, or shorting some cap or diode, etc, could double or halve some current or voltage.If you're lucky, the problem is outside the main chip. Here's the datasheet for the IC, there's probably schematics out there for full DMM's with the IC or something similar. Or might be bigger datasheets with more design guides.I think a lot of diode modes work like resistance modes, by sending out (or sinking) some reference current, like 2mA, and then measuring some voltage drop. And they have some parallel resistance with the current source, to clamp it at 4V or whatever, when the probes are open circuit.If you have another DMM, measure the output I, V, or you could make some circuit (if you have the parts and some know how), to get a rough idea of the current and voltage from the DMM.

author: larrybud
author_rank: Contributor
timestamp: March 29, 2024, 01:26:46 pm
content: I did a little more investigation and started checking every cap on the board.There are two of these caps (see attachment). One reads "103JG" and measures 10nf (in circuit).The attached reads "103JU" and I get no reading with my DMM or ESR (overflow) in circuit, so I pulled it out, and I do get a 10nf reading. Odd that it reads OPEN when installed?
mastech DC POWER SUPPLY - Page 1
Forum section: electronics / repair

author: westerjimmy495
author_rank: Newbie
timestamp: September 04, 2021, 10:44:31 pm
content: The current display stopped working still has the current just no display anyone ever seen this have not removed cover yet getting idea's on what to check any suggestions ...Thanks

author: bob91343
author_rank: Super Contributor
timestamp: September 04, 2021, 10:55:35 pm
content: I never looked at those displays but you can see if there is a poor connection. Otherwise you may have to replace the display, depending on what's wrong.Pull the cover and probe around looking for loose connections.

author: rsjsouza
author_rank: Super Contributor
timestamp: September 04, 2021, 11:49:10 pm
content: The displays on those Mastech power supplies are usually 7106- based DMMs totally independent of their main board, so it becomes almost a replaceable part entirely.For it to die completely, I would suspect power supply to the ammeter (a broken wire, perhaps?) or a complete breakdown of the 7106 (much rarer occurrence IMO).
Mastech HY-3005D-3 Earthing and common ground issue - Page 1
Forum section: electronics / repair

author: Jwillis
author_rank: Super Contributor
timestamp: February 20, 2024, 12:41:05 am
content: I have a problem that I didn't have before. The Positive and Negative(common ground) should float independently from Earth ground, correct?I was trying to work on a op amp powered with a dual rail supply from HY-3005D (in series mode to give me +15v 0v -15v) . Signal from AWG and oscilloscope to monitor the output with my oscilloscope. I hadn't even connected the the circuit yet but was creating a common ground with Hy3005D power supply, Oscilloscope and AWG. Oscilloscope and AWG work fine until I connect the 0v centre tap of supply and the slave side shorts out.I done this configuration without any issue before. Power outputs of power supply should be independent from earth ground.
Mastech M-830B resistor value - Page 1
Forum section: electronics / repair

author: daskorn
author_rank: Newbie
timestamp: August 25, 2025, 09:00:54 pm
content: Hi,I try to repair a Mastech M-830B multimeter. The ohms mode is not working.I noticed that the biggest resistor on the board measures as open circuit. If I bridge it with e.g. a 10 ohm resistor it starts working.I attached a photo of the resistor. Strangely I read the color code as: Braun Black White Gold. Which makes no sense as it represents 10 GOhm.What do you think? Any educated guess is welcome.BRdaskorn

author: wraper
author_rank: Unknown
timestamp: August 25, 2025, 09:08:32 pm
content: Most likely 10.9 ohms. Treat it like 5 ring marking.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 25, 2025, 11:28:10 pm
content: supposed to be the schematicssadly quality is bad

author: gamalot
author_rank: Super Contributor
timestamp: August 26, 2025, 04:51:28 pm
content: It looks like a 39ohm resistor.

author: daskorn
author_rank: Newbie
timestamp: August 28, 2025, 02:43:02 pm
content: Hi,I gave the schematics a try. In addition I found this Russian article with a really nice schematic of the meter:https://www.kipis.ru/upload/kipis_articles/article_m-830b.pdfIn both schematics it seems to be a 2k resistor.Old schematic: R10New: R13I identified it because its wiring to the sector knob and the 1.2M Ohm resistor it is wired to next.Without schematics it would have been impossible to identify, as the color code seems to have changed. Maybe due to heat?Thanks for your support!

author: wraper
author_rank: Unknown
timestamp: August 28, 2025, 04:42:57 pm
content: It's a current shunt, so all you need is to check the current multimeter displays. Then you can easily calculate needed ratio off actual current to make it right, and multiply with existing shunt resistor value.
Mastech MS2108 broken - Page 1
Forum section: electronics / repair

author: dchapman
author_rank: Newbie
timestamp: January 27, 2025, 02:46:18 am
content: Good day.I have a Mastech MS2108 clamp meter that is acting up. On the DC Amps setting the screen reads -0L and the unit beeps about twice a second.The low battery indicator is not on. I replaced the batteries anyways but the issue persists.I contacted Mastech and their tech people are celebrating the new year.Any ideas?Thanks,

author: coromonadalix
author_rank: Super Contributor
timestamp: January 27, 2025, 05:27:40 pm
content: https://www.ic-fortune.com/upload/Download/FS9922-DMM3-DS-12_EN.pdfdatasheet of the dmm chip, schematic in it should helphas it been dismantled or just used, used on the probes input(s) voltages spikes, overload ?

author: dchapman
author_rank: Newbie
timestamp: January 27, 2025, 07:53:22 pm
content: Thank you for your reply and the datasheet. I will study it but most likely it is beyond me.This meter has spent 95% of its life sitting in its case in a toolbox. Never dropped. No temperature extremes. Most measurements have been in the 1.5 to 12VDC range. I did use it once a few years ago to measure the inrush of a 120VAC air conditioner. Most recently used to measure the current draw of a Phillips Respironics CPAP machine.When this problem first started I took the back off looking for obvious problems but saw none and put it back together.Thanks again.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 27, 2025, 08:19:41 pm
content: humidity ?? sitting a long time ... no battery leakage / corrosion ?some in the past talked about the grease used for the dial contacts, they dried them, removed all residues and tried, and it was working ? and re-greased them with more neutral ones

author: dchapman
author_rank: Newbie
timestamp: January 28, 2025, 12:52:52 am
content: Hi. Thank again.It was stored indoors in a tool box. No liquids. No battery leakage or corrosion.Somewhere I have contact cleaner I used to use on TV channel changers. I'll see if i can find it.
MASTECH MS8211D Pen type multimeter fails to turn on after a year of storage - Page 1
Forum section: electronics / repair

author: Watcher
author_rank: Contributor
timestamp: August 04, 2024, 07:26:16 am
content: Hi,I bought the above multimeter about 2 years ago. Barely used a had-full of times and then stored for a year unused.I tried to use it the other day with new batteries only to find out that it doesnt turn on!There is another older thread with a similar case here with the same type of multimeter!Not happy at all with Mastech!I wonder if anyone has found anything on this...

author: beatman
author_rank: Regular Contributor
timestamp: August 04, 2024, 07:58:33 am
content: Are you left the old batteries in when storage the meter?If yes then maybe leaked the old one and damage the device.It happens to me with one expensive clamp meter from extech won't turn on after few months.With one first look i can't see the liquid inside but after opened and look careffuly i see the damage.After a lot of detailed cleaning and meny meny tries and tests my meter works again.Never again alkaline batteries on all my meters only NiMh.
Mastech MS8212A Pen type multimeter doesn't switches ON normally - Page 1
Forum section: electronics / repair

author: abhishekkumar1902
author_rank: Regular Contributor
timestamp: December 21, 2021, 05:13:04 pm
content: Hello Friends,I have aMastech MS8212Apen-type multimeter which I bought two years back, didn't use it at all but kept it in there as it is with the batteries removed.Yesterday when I put on the batteries and tried switching it ON, it didn't turn ON at all. I tried with another set of batteries, also with a bench power supply as well, but it didn't switch ON when the rotary knob was turned to any of the four working positions. However when I press those MAX, RANGE, etc buttons, they gave a beep sound that means the circuitry was at least turned ON but nothing o the display.After a few hit and trials, I observed that the multimeter switches ON successfully when I QUICKLY (like within 500 milliseconds instantly) turn the rotary knob to either the LOGIC or VOLTS position, and then it continues to work in all other four positions until I turn it back to OFF position. However, it does not switch ON if I normally turn the rotary to know to any of those four working positions.Issue video:https://youtu.be/90gSqvFYX7wWhat could be faulty?Any help is appreciated

author: crastor
author_rank: Newbie
timestamp: May 28, 2022, 10:58:10 am
content: I am a hobbyist electrician. I have a Fluke 116/323 kit HVAC Multimeter. I think it's one of the most reliable brands on the market.Measure 400 A ac current600 v ac, and dc voltage.
mastech triple power supply spiking - Page 1
Forum section: electronics / repair

author: garydirkse
author_rank: Newbie
timestamp: January 30, 2024, 02:39:40 am
content: My new Mastech linear triple power supply produced intermittent spikes to 56 Volts! I found cold solder joints by pulling on diode leads years ago. The problem persisted and destroyed a few items so, I put it on the shelf for years. Once powered down and back on it behaved until it was ignored then lost control of he slave regulator. Comparing Voltages from the master regulator to the slave regulator, two pins on N1 differed by about 400mV. V6 a 6.2V zener had shorted somewhat. A new zener cured it. If you replace a zener, use long leads to space the diode a half inch above the board. I had built a monitor to alert me when the beast was losing control and tried freeze spray etc..Finally, aldue

author: Jwillis
author_rank: Super Contributor
timestamp: January 30, 2024, 05:11:30 am
content: Another problem that can cause weird voltages and funny current limiting is wore out pots. Problem is finding 6K pots from general vendors.
MATSUSHITA PANASONIC AM4100 MICRO SWITCH - Page 1
Forum section: electronics / repair

author: asterone
author_rank: Contributor
timestamp: March 10, 2021, 10:06:36 pm
content: Hi, I'm repairing a Sanyo stereo unit and it seems 2 of the micro switches have failed so I'm looking for some technical details and replacements for them, MATSUSHITA PANASONIC AM41008 MICRO SWITCH.Ive done a search online but it seems these are outdated and little info is available let alone exact replacements. As these have specific screw holes in the stereo chassis, direct replacements would have been preferred, so perhaps any suitable micro switch suggestions and then I could probably 3D print an adapter of sorts.

author: perieanuo
author_rank: Frequent Contributor
timestamp: March 11, 2021, 06:50:36 am
content: hi,if you don't find easily those switches on farnell or so, adapting standard microswitches should be a walk in the park

author: asterone
author_rank: Contributor
timestamp: March 11, 2021, 09:35:53 pm
content: Yep, more than likely what i will do, i was hoping though that someone would be able to provide some technical specs on that micro switch so i could find a very close match. Seems i will need a low force acuation switch.
MAX3227 can't work on Low temperature with 0.1uF - Page 1
Forum section: electronics / repair

author: heroxue
author_rank: Newbie
timestamp: January 11, 2024, 04:48:28 pm
content: Hello everyone,I have just used MAX3227 for RS-232 communication at 3.3V. However, I observed that the chip doesn't function properly with C1-C4 (0.1uF 2X1 Ceramic Multilayer Capacitor) in the temperature range of -30 to -10℃. Surprisingly, it works at -40℃. I tried increasing the capacitance of C1-C4 to 0.2uF, and occasionally, it starts working properly (at -30 to -10℃), and it still works fine at -40℃. When I increased the capacitance of C1-C4 to 1uF, the chip works flawlessly across the entire temperature range. Could you please help me understand the underlying issue?Kun.

author: David Hess
author_rank: Super Contributor
timestamp: January 11, 2024, 05:27:01 pm
content: What dielectric are the ceramic capacitors using? The higher class dielectrics lose capacitance outside of their temperature range.

author: wraper
author_rank: Unknown
timestamp: January 11, 2024, 05:57:10 pm
content: There are several things in question here. Is MAX3227 genuine? Is it variant that is rated to operate at negative temperature or just 0°C to +70°C (although they still most likely would work the same). What ceramic type? Is it X7R, Y5V or what?

author: heroxue
author_rank: Newbie
timestamp: January 11, 2024, 06:09:50 pm
content: Quote from: David Hess on January 11, 2024, 05:27:01 pmtype 2 dielectric (X7R)

author: heroxue
author_rank: Newbie
timestamp: January 11, 2024, 06:17:46 pm
content: Quote from: wraper on January 11, 2024, 05:57:10 pmThe chip is a genuine chip, rated at -40 ° C to+85 ° C, and approximately 10% of the chips (out of a total of 100 chips) cannot operate at negative temperatures. The capacitor material is X7R，It seems that the change in capacitance value is not the true reason why the chip cannot work, and the temperature range of X7R capacitance value reduce in the entire temperature range shown in the figure is inconsistent with the temperature range at which the fault occurred,It cannot explain why the chip can work at -40 ℃.
Maybe Dave should make this a stickie - Page 1
Forum section: electronics / repair

author: scopeman
author_rank: Frequent Contributor
timestamp: February 07, 2022, 09:25:59 pm
content: Dave,Perhaps you should make this a stickie and have the attachment in the stickie and also put this in the Test and Measurement section as well.Tek Troubleshooting OscilloscopesSamW3OHM

author: whatboy
author_rank: Regular Contributor
timestamp: February 09, 2022, 07:45:35 am
content: Already in the first thread...

author: magic
author_rank: Super Contributor
timestamp: February 09, 2022, 12:58:50 pm
content: This illustrates the main problem with stickies: few people read them

author: Shock
author_rank: Super Contributor
timestamp: February 09, 2022, 04:33:59 pm
content: Never ask Dave to sticky your attachment.

author: tautech
author_rank: Super Contributor
timestamp: February 10, 2022, 10:24:06 am
content: Quote from: scopeman on February 07, 2022, 09:25:59 pmAlready linked mid 2014 in this now sticky thread:https://www.eevblog.com/forum/repair/repair-documents-and-links-sticky-me-please-mods/

author: Shock
author_rank: Super Contributor
timestamp: February 10, 2022, 10:39:57 am
content: The repair section is an eevblog success story, one of the most popular forums now.Tautech and I were early believers.
MB3773 power supply monitor - Transistor short ? - Page 1
Forum section: electronics / repair

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 17, 2019, 08:39:55 am
content: Hi,I am trying to repair a CDI (Capacitor Discharge Igniter) Ignition Unit from a motocycle. I am stuck to diagnose stage since all parts seem to be ok except a PNP SOT23 transistor marked with the code L6 (BSS69 and BSS70) that is connected directly to a power supply monitor MB3773 at pin 2 which is the RESET.This transistor seems to have short from Base to Collector. I am not sure if under the L6 SMD is a rail that connects BC but I didn't see anything like that until now.Also, the Base does not seem to be connected somewhere....So, do you think that this transistor is faulty? Is the connection between Base-to-Collector (shorted) normal?

author: fzabkar
author_rank: Super Contributor
timestamp: July 18, 2019, 10:40:52 pm
content: FWIW, the shorted base-collector configuration is often used in current mirrors:https://physics.stackexchange.com/questions/371360/whats-the-purpose-of-shorting-the-base-and-collector-of-a-transistor-in-current

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 19, 2019, 11:16:46 am
content: Yes, you have right.... Under the SMD transistor, there is indeed a tray that connects Base-Collector.Out of the circuit, the transistor works as expected.
MB85RC04 Dump extraction in RT809H -> Help! - Page 1
Forum section: electronics / repair

author: Franc
author_rank: Regular Contributor
timestamp: December 18, 2022, 12:10:34 pm
content: Hello all!I'm trying to Dump the memory FRAM MB85RC04 Fujitsu.My reader the RT809H but there is no data base for this chip, see attached.It looks similar 24cXX 2-wire memory.Anyone knows what other compatible memory I can use in RT809H for this dump extraction? I'm worried to crack the dump or chip.Nice week!! Thanks!!

author: wraper
author_rank: Unknown
timestamp: December 18, 2022, 12:31:28 pm
content: Most likely it's compatible with 24C04.

author: fzabkar
author_rank: Super Contributor
timestamp: December 18, 2022, 07:34:40 pm
content: Datasheet:https://datasheet.lcsc.com/lcsc/1811141412_FUJITSU-MB85RC04VPNF-G-JNERE1_C8738.pdf
MC1466 - Page 1
Forum section: electronics / repair

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 01, 2023, 01:53:07 pm
content: Rebuilding a Lambda LP 522 FM PS and wondered if anyone has any experience buying MC1466 from China?Just wondering if anyone has received good or bad parts.wally

author: coromonadalix
author_rank: Super Contributor
timestamp: June 01, 2023, 03:51:28 pm
content: could be fakes or not ....https://tubetime.us/index.php/2014/09/28/a-miniaturized-discrete-mc1466/https://www.eevblog.com/forum/repair/making-replacement-for-mc1466l/

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 01, 2023, 08:00:55 pm
content: Yea, I saw that home made ship with SM parts. Looks like a lot of work.

author: Jwillis
author_rank: Super Contributor
timestamp: June 05, 2023, 06:06:20 am
content: Quote from: Wallace Gasiewicz on June 01, 2023, 01:53:07 pmDid A few years ago and they were fine. Both MC1466L an MC1566L through Ebay . New old stock. Can't vouch for any recent vendors now. Couldn't say if they are fake or not. Being really shiny with bright white ink I would be skeptical about the date codes. I would take the gamble just to see if they work. But that's me.Did purchase the SMD OSHPARK boards fairly cheaply but haven't got around to using them.
Mc68020  vme bus and scb68155  - Page 1
Forum section: electronics / repair

author: usefi5961
author_rank: Newbie
timestamp: August 11, 2025, 07:41:57 am
content: Hello everyone,I have problem in vec 1.2(vme cpu card)in scb68155 .pcb instead of scb68155 have child board with 2 pal16l8 that .jedec files inside missed ,as a schematic of card scb68155 is originally I insert scb68155 in socket and now system boot and keyboard and monitor working but io card not communicate to cpu and cpu can't read signals from digital and analogue inputs and not command to output. With hand drawn i show in attachment tracking as scb68155 does any one help me?
MCE MT72030D complementary pot/encoder help - Page 1
Forum section: electronics / repair

author: SoundLockEng
author_rank: Contributor
timestamp: September 16, 2019, 05:24:51 pm
content: Hi All,Im looking for a bit of advise on something.I am repairing a mixing console (Neve 66 series) and have come across what feels like a rotary encoder knob but appears to be some sort of specialist half pot half encoder hybrid using an IC called an MCE MT72030D for which I can find no information about whatsoever... one of these encoders has been crunched and is destroyed and needs replacing. If anyone has any insight into how this chip works and the way the special encoder works would be really helping.All the bestChris
MCH-305D-II bench power supply can't change current on one channel - Page 1
Forum section: electronics / repair

author: cozycactus
author_rank: Newbie
timestamp: April 30, 2024, 03:10:00 pm
content: someone have advice on repairing this bench power supply?right channgel 0-30v works good, but left one i can only change voltage, but when i short the +- outputs i have constant current of approximately 4.5A that i can't change with current potentiometers.

author: teatime
author_rank: Contributor
timestamp: May 01, 2024, 01:45:19 am
content: The current potentiometer maybe aged.you can try to replace a new one.

author: teatime
author_rank: Contributor
timestamp: May 01, 2024, 01:49:06 am
content: Attached please find the schematic of this power supply.

author: cozycactus
author_rank: Newbie
timestamp: May 01, 2024, 02:11:25 am
content: thanks. its linear psu , not spsu as in your schematic

author: m k
author_rank: Super Contributor
timestamp: May 07, 2024, 10:48:31 am
content: It can still be a pot problem.There can also be multiple pots in series.https://www.eevblog.com/forum/repair/looking-for-the-schematic-of-a-dual-30v-5a-psu-clone/
McIntosh front panel paint blisters: What's the exact right touchup paint? - Page 1
Forum section: electronics / repair

author: cvanc
author_rank: Frequent Contributor
timestamp: August 15, 2023, 09:37:03 am
content: Anyone here had to fix those infernal paint peels and bubbling on old McIntosh faceplates?I've got one in front of me and can verify Testor's gloss black in the little bottle is real close but doesn't quite exactly match. Is there a known good paint for this? Please share what you've heard and thank you very much.
MCM68766 EPROM equivalent for my programmer? - Page 1
Forum section: electronics / repair

author: Staffan321
author_rank: Regular Contributor
timestamp: May 15, 2022, 07:29:49 pm
content: Hello,I have an MCM68766 8x8 Kib EPROM (https://www.datasheets360.com/pdf/-853472034809684633) that I would like to read with my TL866+. Does anyone have a suggestion for an equivalent that I can select as IC? This is a DIP24 and not a DIP28 like the 2764.Many thanks in advance!Regards,Staffan

author: edavid
author_rank: Super Contributor
timestamp: May 15, 2022, 09:03:14 pm
content: I don't see one in the supported device list. I think you will have to make a socket adapter and use the 2764 setting. The easiest way is to use 2 wire wrap sockets.

author: fzabkar
author_rank: Super Contributor
timestamp: May 15, 2022, 09:49:04 pm
content: Look for something like this:https://www.gotek-retro.eu/c64-2364-eprom-adapter/

author: srb1954
author_rank: Super Contributor
timestamp: May 15, 2022, 10:00:32 pm
content: Quote from: Staffan321 on May 15, 2022, 07:29:49 pmCheck to see if your programmer has a device selection for MCM68366, which is the equivalent mask ROM to the MCM68766. There may be other manufacturer's mask ROMs that have the same pin-out as well.If you can find an equivalent mask ROM selection you will be able to read the contents of the MCM68766 EPROM but I don't think you will be able to program the MCM68766 on the TL866 as it requires a 25V programming supply.

author: edavid
author_rank: Super Contributor
timestamp: May 15, 2022, 10:17:33 pm
content: Quote from: srb1954 on May 15, 2022, 10:00:32 pmThe TL866 does not support any parts like that.
MDF3N50 replacement for a Sony KDL-75W855C Backlight Driver MOSFET - Page 1
Forum section: electronics / repair

author: Club_Michas
author_rank: Newbie
timestamp: August 13, 2022, 12:58:08 pm
content: I'm currently trying to repair the Backlight of a Sony KDL-75W855C LCD TV.1/4 of the LEDs does not Light upand the TVsPower LED is blinking 6 Times Redafter the Sony Logo appeared.I shorted BL_ERR to Ground and the Tv is booting into Android but the Backlight is Turning of after the Sony Logo.Because I don't have Access to the Schematics I checked some Voltages and It looks like that1 of the 4 Backlight MOSFETsseams to be faulty but I can't get this MOSFET on Digikey.I contacted the Support for a suitable replacement but the couldn't help me out.Does anybody know which MOSFET could be suitable as aDrop in replacement for MDF3N50?Thanks you everybody on advance for your help.

author: m k
author_rank: Super Contributor
timestamp: August 17, 2022, 07:25:22 pm
content: 3N50 is pretty much 3N50, just find correct casing and you should be fine.First I found was a bit slower but still clearly in MHz class.Original Rds(on) is also already quite high so it shouldn't be a big problem.

author: fzabkar
author_rank: Super Contributor
timestamp: August 19, 2022, 05:46:40 am
content: Just in case you need the datasheet ...https://www.magnachip.com/wp-content/uploads/2020/10/MDF3N50-2.pdf
MDH industries, RACAL 2025 series xray electrometer repair - Page 1
Forum section: electronics / repair

author: richnormand
author_rank: Unknown
timestamp: January 08, 2020, 06:36:05 pm
content: Has anyone ever had an MDH Industries (AKA RACAL 2025 series) to repair?Got this unit with the connecting cable cut and partially disassembled from previous repairs. It was free so I cannot complain.Any info, schematics, pinouts would save me lots of reverse engineering time at this stage.Only info I got from Google was a reference in a book comparing various instruments from the 1980s.Cheers and thanks.
Mean Well 100W 12V PSU GND and Earth pin mutual resistance? - Page 1
Forum section: electronics / repair

author: Pythzepf
author_rank: Newbie
timestamp: July 07, 2019, 09:58:49 am
content: Hi!I'm working with a power supply LRS-100-12. In short it is a 100-230 VAC in 12V 100W out isolated power supply. I discovered by accident (magic smoke involved!) that some of the power supplies measure a resistance between its output GND and the chassis Earth. This value ranges from a few ohms to open (infinite resistance).As seen in this image taken from the device's datasheet, there is a filter capacitor between GND and Earth. As I understand, this is there to filter out high frequency noise from GND. However the resistance between these pins should measure open, since capacitors present an infinite resistance to DC current/voltage (the voltage injected by multimeter probes in Ohm mode).Question:is low resistance measured between these pins some anomaly, are some of the PSU's simply defective (or somehow damaged by me), or am I missing something? Thank you!

author: Gyro
author_rank: Super Contributor
timestamp: July 07, 2019, 11:36:04 am
content: What value of resistance are you measuring? It may be that there is a high value discharge resistor wired across the capacitor and not shown on the block diagram.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 07, 2019, 12:38:05 pm
content: Normally they are protection device like movs, sometime blue colored "look a like capacitors" we have them on some psu's we use, they are in the "k" ohms value in my caseIn your psu, you have 3 of them almost in the middle of the psu, you see them thru the grid.MOV'S tutorialhttps://www.electronics-tutorials.ws/resistor/varistor.htmland another onehttps://www.nist.gov/sites/default/files/documents/pml/div684/MOV_announce_color.pdf

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 07, 2019, 11:45:57 pm
content: AFAIK there's always a capacitor between primary and secondary sides of the transformer.When a ground connection is provided to the primary side it is a common practise to also link PSU frame and secondary "negative" to ground. (This has the advantage of draining the away the current leaked through the previously mentioned capacitor as it can give you a tingle in the right conditions.)
Mean Well EPP-400-12 – please help to find out clamp components values - Page 1
Forum section: electronics / repair

author: SergiiB
author_rank: Contributor
timestamp: March 17, 2024, 10:05:42 am
content: I have a power supply EPP-400-12 that has failed. The power supply consists of a main board and an additional board RPS-400B-R8 which from the reverse engineering looks like a standby power supply and some protection circuitry.Visual inspection of the main board shows no damage, checking capacitors, full bridge rectifier etc. shows no signs of short circuit, burning or cracks.The only place that has visual damage is the clamp circuit on the additional board and it looks like this:It can be seen that the resistor on the right (R908) is totally missing, the trace that connects the capacitor and the first resistor (R907) is missing as well. Also, there is a piece of the surface missing between the ground contact and the missing R908 resistor.My thought is that there was a spark or some connection between ground contact and the missing R908 resistor where voltage is high as it is clamp circuit.There reverse engineered circuit is this:I have highlighted the missing component and the missing traces.One of two resistors survived and has value 104, capacitor is chipped and cannot be measured. So, my question is what would be the values of the capacitor and the second resistor of the clamp circuit?Can I assume that the second resistor is 104 as well as they used two instead of one to divide the heat dissipation?And what would be the value and voltage of the capacitor? The voltage that goes on the + contact is taken from the 220uF 400V capacitor of the full bridge rectifier.Regards, Sergii

author: asis
author_rank: Frequent Contributor
timestamp: March 17, 2024, 02:28:38 pm
content: Hi,Check out the pdf.Denominations are indicated.Both resistors are 100k.In addition to the TNY286, the phototransistor of the optocoupler may be damaged.Most likely this is the impact of lightning.https://datasheetspdf.com/pdf-file/1469865/PowerIntegrations/TNY286DG/1

author: SergiiB
author_rank: Contributor
timestamp: March 17, 2024, 02:34:13 pm
content: Thank you.But this is completely different clamp circuit, the resistor is in series there.Noted about the optocoupler, will replace it just in case as well.Regards, Sergii
Mean Well HDR-150 - Page 1
Forum section: electronics / repair

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 10, 2023, 04:57:00 pm
content: I got one more unknown 6-pin chip. It is situated in the secondary side of a power supply. I guess it is an over voltage protection circuit (?). It looks like it is an opamp (possibly with voltage reference).It's code is A5195P. Have anybody some clue about this part?

author: fzabkar
author_rank: Super Contributor
timestamp: November 11, 2023, 05:52:26 am
content: I tried to find some Mean Well PSU circuit diagrams.FWIW, I found this one:https://elektrotanya.com/mean-well_psp500-48_sch.jpg/download.htmlThere is an M51957B chip on the secondary side:https://docs.rs-online.com/4d41/0900766b80c2db9a.pdf(datasheet)This is a reset supervisor IC with different pinouts and packages, so the similar part number may be a pure coincidence. You might like to take the 8-pin part and ignore the NC pins, and then compare it against your 6-pin part ...That said, this spec sheet does refer to OVP ...https://www.meanwell-bg.com/files/M2020/HDR/HDR-150-spec.pdfI hope I haven't introduced a red herring.

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 15, 2023, 03:39:26 pm
content: I accidentally found that there is whole AP43XX opamp family. So it could be AP4312, AP4313 or AP4320 (SOT-23-6). I haven't checked it yet, but I now see AP431X family is used in other Mean Well power supplies.I mean SO-8 AP4310A is used a lot (this is opamp + precision voltage source), so unknown SOT-23-6 chip can possibly be from AP43XX series too. I'll investigate it next days.Upd.: Pinout says it can be AP4320.Upd.2: Datasheet says AP4320 has two options, A and B, 30 mV and 50 mV current sense protection. So, I ordered both, will see what suits better. Power supply under repair has 0.01 R shunt and is 3 A rated, so 30 mV option seems a bit low but 50 mV option seems a bit high.

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 30, 2023, 01:53:14 pm
content: Yes, A5195P (or A5190F) code is AP4320AK or AP4320BK, both works (chips arrived today). The only difference between -AK and -BK is current protection setting, and it is about 3.7-3.8 A with AP4320AK and it is about 4.7-4.8 A with AP4320BK. Both settings are fine for HDR-150-48.PCB revision is HDR-150-R3.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 30, 2023, 05:58:55 pm
content: did that fix it?.

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 30, 2023, 08:19:22 pm
content: Quote from: p.larner on November 30, 2023, 05:58:55 pmYes. I had symptoms that clearly showed broken opamp (too high output voltage, optocouplers were replaced and nothing else seems to be broken). After its replacement the power supply works fine.
Mean Well MDR-100 PWM IC controller - Page 1
Forum section: electronics / repair

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 07, 2023, 02:25:25 pm
content: Hello. Repairing broken MDR-100-24 I found strange PWM IC controllers with a code 6C17703 and another revision with a code 6C19910. Google can't help. What is that?By pinout it is similar to NCP1200, NCP1239 series used in other their power supplies.I have several MDR-100 power supplies with a two revisions which look the same. One revision is MDR-100NA-R4 and another revision is MDR-100NA-R6. The only difference I see is different PWM IC controller codes.Photo taken from MDR-100NA-R4.

author: 2N3055
author_rank: Super Contributor
timestamp: November 07, 2023, 02:42:10 pm
content: FA5640 ??

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 07, 2023, 02:48:35 pm
content: Yes, it can be.I will look at datasheet now to investigate if it is Fuji FA5640N or not.Thank you very much!

author: fzabkar
author_rank: Super Contributor
timestamp: November 07, 2023, 05:03:13 pm
content: https://www.aliexpress.com/w/wholesale-FA5640.html?initiative_id=https://ae01.alicdn.com/kf/H8adc1659c6904c8d8971abdf0cc35567u/100-New-original-5640-FA5640-FA5640N-SOP-8.jpg

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 07, 2023, 07:48:17 pm
content: Thank you,, @fzabkar, it seems I can find this IC on our local market. I ordered one already for test.

author: Vovk_Z
author_rank: Super Contributor
timestamp: November 08, 2023, 07:51:51 pm
content: Yes, that was FA5640N.It had several other small components broken on a secondary side too (mostly semiconductors: PC123 optocouplers, AP4310A opamp, etc).