hybridfree/eevblog-posts huggingface dataset:
Multimeter Nonsense Readings - Page 1
Forum section: electronics / repair

author: phillium
author_rank: Newbie
timestamp: June 26, 2023, 07:51:10 pm
content: I recently bought a lot of multimeters with the description "Some Work, Some Don't" and now I'm trying to figure out what actually needs fixing. Some of them seem to measure correctly, but will display either offset (ie nonzero) DCV readings or constantly climbing readings when not connected to anything to read. Is this actually a problem, or is it OK as long as they read a known value correctly?PS. All of the examples I can remember do this for DCV specifically, not ACV or impedance or anything else.

author: Greybeard
author_rank: Frequent Contributor
timestamp: June 27, 2023, 06:39:11 am
content: High impedance adc tend to count up or count down display due creeping currents.If shorted input is steady near zero it's OK.

author: bdunham7
author_rank: Super Contributor
timestamp: June 27, 2023, 06:43:49 am
content: Quote from: phillium on June 26, 2023, 07:51:10 pmBefore you ask us to think about multimeters, please tell us exactly which models you have so that appropriate answers can be given.Meters with high-impedance ranges do drift up or down on the lower voltage ranges when there is no input.

author: phillium
author_rank: Newbie
timestamp: June 27, 2023, 04:36:45 pm
content: The two I'm most concerned with are Fluke 8808A's, although I still have to take a harder look at a couple of Keithley 2700's.Edit: After shorting the inputs I saw stable, near zero DCV readings. Thanks for the tip Greybeard!

author: bdunham7
author_rank: Super Contributor
timestamp: June 27, 2023, 10:37:05 pm
content: Quote from: phillium on June 27, 2023, 04:36:45 pmThose are high-impedance in the 200mVDC and 2VDC ranges only. In those ranges they will slowly count up or down as the small input bias current charges up the input capacitance. 20V and up ranges are 10M and won't do that. As you've observed, shorting the inputs brings the input voltage back to zero. This behavior will not affect actual voltage readigs because the input bias currents are very low, tens of pA.
Multimeter OLED Replacement UT171C - Page 1
Forum section: electronics / repair

author: m0p3d
author_rank: Newbie
timestamp: September 07, 2021, 05:44:54 pm
content: Dear all,have one very nice UT171C multimeter. Unfortunately due to (assumed) aging of the oled - its barely readable even in darkness and 100% brightness. Since i bought it there were max 3 hours of operation- but its already 3years ago.Found this:https://www.eevblog.com/forum/testgear/ut171c-teardown-(lots-of-pictures)-various-notes/Agree with the statement of @DigitalCorpusNope, but the following is printed on the assembly:"100106702f B 3" on the back of the glass"1930114308102182602R" on the FPC.The driver is the SDS1305T7 and its a 2.7", 128x64 screen.The FPC assembly is 2 part that is glued/taped to the custom, 22-pin cable and originates as a 31-pin cable with a ~0.65 mm pitch. The 22-pin piece is a ~0.3 mm pitch FPC.Does anybody know where to get replacement unit or which unit to use/modify (pin asignment) to get another new bright display in. Maybe there is an option to retrofit to EBTN ?
Multimeter readings don't change - Page 1
Forum section: electronics / repair

author: brockles
author_rank: Newbie
timestamp: March 17, 2022, 09:36:13 pm
content: Picked up a cheapish Fluke 787 for repairs. I can select different modes and they show their standard baseline value but when I try to take a reading on any mode, the values don't changes. Had a quick look inside and nothing immediately looks damaged. First port of call will be to check the jacks but what are the next steps if they prove to be fine?Many thanks

author: thm_w
author_rank: Super Contributor
timestamp: March 17, 2022, 09:58:56 pm
content: After checking jacks maybe check under the range switch:https://www.eevblog.com/forum/repair/fluke-787-repair/https://www.eevblog.com/forum/repair/fluke-787-repair-any-idea/
Multimeter repair - final desicion? - Page 1
Forum section: electronics / repair

author: marekpasek
author_rank: Contributor
timestamp: November 28, 2019, 10:43:58 pm
content: Hello everybody,I have a malfunctioned multimeterMetex m4650cr. I have created a thread about it already (https://www.eevblog.com/forum/repair/metex-m-4650cr-multimeter-repair/msg2804114/#msg2804114) and I got some interesting feedback. Check it out if you are interested.To make long story short my unit has a constant deviation of 22% on all ranges of DC, AC, DV and AV. Other functions work correct with remarkably low offset after 25 years since calibration. The problem until now was that I could not find any service manual which would tell me what values the passive components in the unit should have and therefore I could not compare them with values I measured by another multimeter (my first assuption was that the deviation is caused by some burned resistor which messes up with some voltage divider ratio thus feeding wrong values into the ADC).However, recently I found a service manual for a similar meterMetex m4650B. There are the values and the circuit shows some similarities with what I observed in the *cr model. Most importantly there is the low value resistor I found burned in my unit (discussed in the original thread). The value in *B model should be 1 ohm whereas I measured 2 ohm in my unit. Also in the service manual there are trimmers sorted by what range they trim.So there comes the question.Do you think the low value resistor causes the problem? Should I replace it if it does? And would it also work if I just compensated for the deviation via the corresponding trimmer?Thank you.Service manual and picture attached below:

author: iMo
author_rank: Super Contributor
timestamp: November 28, 2019, 11:22:58 pm
content: Why do you need two threads for the same repair?

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 29, 2019, 08:11:34 am
content: It is quite annoying for forum database cluttering, future searching and general following of "a" subject.

author: marekpasek
author_rank: Contributor
timestamp: November 29, 2019, 09:48:24 am
content: Sorry for that. I am used to do that from other fora. In certain type of fora it is undesirable to make long conversation and vice versa it is appreciated if broad topics are "chopped" to shorter subtopics. Although it is important to note that it is common mainly in those fora where topics are listed by time of uploading, not by time of the last reply (the case of EEVBlog).
MULTIMETER ST-9912 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: February 23, 2021, 08:53:46 am
content: Good morning all! I am looking to find 2 voltage regulators (marked: U4 and U5), for an ST-9912 multimeter; the original regulators are not the correct ones. I have attached the pictures of the multimeter. Thank you for your help.
MULTIMETER UNI-T 58B - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: December 11, 2024, 09:50:09 am
content: Hello; I am looking for someone who could take several photos of the central switch alone with the position of the contacts of the UNI-T UT58B multimeter (above/below).....Thank you in advance for your dedication

author: Overspeed
author_rank: Frequent Contributor
timestamp: December 14, 2024, 04:16:52 pm
content: HelloBetter to post in repair section / thread as that far to be a metrology instrumentI suppose you need a picture of the PCB for the angular position of the knob .RegardsOS

author: lionelkjh
author_rank: Frequent Contributor
timestamp: December 20, 2024, 06:24:38 pm
content: Good evening; I am closing this discussion.....

author: mendip_discovery
author_rank: Super Contributor
timestamp: December 20, 2024, 07:00:10 pm
content: Panto, OH NO YOU'RE NOT!

author: Overspeed
author_rank: Frequent Contributor
timestamp: December 21, 2024, 01:51:02 pm
content: Quote from: lionelkjh on December 20, 2024, 06:24:38 pmHelloThis is a forum ( and a very useful forum ) not a jungle , you ask a question , ok , I provide you an answer .... my assessment is still : metrology is not the right place for this question .Regards from FranceOS

author: lionelkjh
author_rank: Frequent Contributor
timestamp: December 22, 2024, 09:53:13 am
content: HELLO; unable to delete the previous message, I therefore moved the message to 'repairs': PLEASE BE UNDERSTANDING AND DO NOT UNLOAD YOUR BAD MOOD ON ME!

author: Halcyon
author_rank: Unknown
timestamp: December 22, 2024, 10:03:34 am
content: Quote from: lionelkjh on December 22, 2024, 09:53:13 amYou can delete your own replies to a thread, but not entire threads, even if you started them. Moderators can delete entire threads or move them for you.

author: lionelkjh
author_rank: Frequent Contributor
timestamp: December 22, 2024, 11:55:22 am
content: Hello; ok; thank you for answering so quickly and especially so kindly!
MULTIMETER UNI-T UT58B - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: December 20, 2024, 06:22:14 pm
content: Hello; I am looking for someone who could take several pictures of the central switch alone with the position of the contacts of the UNI-T UT58B multimeter (above/below).....Thanks in advance for your dedication;)

author: Halcyon
author_rank: Unknown
timestamp: December 22, 2024, 10:04:43 am
content: Duplicate thread.
MULTIMETER WURTH HELP! - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 11, 2025, 07:51:06 am
content: Hello everyone! The integrated circuit of my WURTH multimeter is defective (DTM0660L); it only works in manual mode and no longer in automatic range, for all electrical quantities to be measured.....Looking more closely at the card; a 5-pin area must be used to read and reprogram....I plan to replace it, I have 2 programmers: the TL866 and the RT809H but I don't know how to read the content and put it back on the new circuit using these 2 programmers....I took a photo of the multimeter card with the circuit datasheet....Thank you in advance for your enlightened advice....Cdt

author: ondraN
author_rank: Regular Contributor
timestamp: March 11, 2025, 09:28:30 am
content: That IC will very likely be locked for reading.

author: tunk
author_rank: Super Contributor
timestamp: March 11, 2025, 12:20:36 pm
content: The picture is unclear - the 8-pin chip below could be an eeprom.Edit: And please don't double post.

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 11, 2025, 04:49:37 pm
content: HELLO! My problem only concerns the big integrated circuit at the top, and not the eeprom....The image is perfectly usable.....Cdt

author: tunk
author_rank: Super Contributor
timestamp: March 11, 2025, 06:29:59 pm
content: From the datasheet:"2.9 Measurement function definition with the EEPROM and calibration."So this setting may be in the eeprom and not the chip.

author: Simon
author_rank: Unknown
timestamp: March 11, 2025, 06:39:24 pm
content: seriously? you have been here long enough that duplicate threads will just piss everyone off! :https://www.eevblog.com/forum/beginners/multimeter-wurth/msg5844363/#msg5844363
multimetre Value - Page 1
Forum section: electronics / repair

author: yalect
author_rank: Regular Contributor
timestamp: February 12, 2020, 10:08:08 pm
content: Hello,I have the following multimetreMultimetrixcm 625when I adapt it to measure current for exampleVolteor ampere it doesn't give me 0 Value to start measure and for 220 Volte indicate240 Voltelike it's showen on the Picturemay you Have an Idea?

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 13, 2020, 12:29:15 am
content: Can you show us the insides?I think this is going to be the same as the Taiwan-made Metrix MX355.There should be trimpots to adjust just about anything, the problem is finding the right one, so be prepared to gather all the necessary to recalibrate it completely.

author: Haenk
author_rank: Super Contributor
timestamp: February 13, 2020, 10:51:57 am
content: Too little information.What is the zero value like? 0,1V, 10V, 100V?And did you measure the mains voltage with a certified/known good multimeter? I don't know which country you are living in, but most countries don't have 220V any more, it's usually 230V and then within the upper range of the allowed mains voltage, i.e. 240V is rather common.
multimetroUNIGOR A43  il capacimetro segna meno del reale  - Page 1
Forum section: electronics / repair

author: GIUSE
author_rank: Newbie
timestamp: December 12, 2020, 09:17:38 pm
content: Ciao a tutti ,sono Giuseppe dall italia (torino),ho acqistato dall austria due multimetri unigor A43 ,ma entrambi hanno i capacimetri che segnano meno del reale. Tutte le altre funzioni sono ok. Ho controllato tutti i componenti e sembrano ok. Sono un elettotecnico hobbista. Potrebbe darsi che abbia controllato male qualche cosa. Tra l altro ,lo schema che si trova in giro non e del tutto identico. Chiedo gentilmente ,se qualcuno che li ha gia riparati mi puo aiutare . Grazie anticipate.
Multiplex or Non-Multiplex - Page 1
Forum section: electronics / repair

author: Jwillis
author_rank: Super Contributor
timestamp: June 15, 2023, 09:00:08 pm
content: I'm wanting to fix an old Multimeter because it has a certain sentimental value to it.I think I identified the chip used as an ICL7106 3 1 /2 Digit, LCD Display, A/D Converter. I based it on the surrounding components, values and pin configuration.I removed the original COB chip as all it did was create heat when voltage is applied.As you can see there is room to accommodate a 40 pin PDIP .My problem began when searching the data sheet I ran into a degree of confusion. Now I'm second guessing my order.The First data sheet from MAXIM states that it drirectly drives a NON-Multiplexed LCDhttps://pdf.datasheetcatalog.com/datasheets/560/382681_DS.pdfOther data sheets from RENESAS, INTERSIL, and HARRIS state that it includes a Multiplexed Back plan Drive.https://www.renesas.com/us/en/document/dst/icl7136-datasheet?r=505941https://pdf1.alldatasheet.com/datasheet-pdf/view/67425/INTERSIL/ICL7106.htmlhttps://pdf.datasheetcatalog.com/datasheet_pdf/harris-semiconductor/ICL7106CM44_to_ICL7107RCPL.pdfYet the Pin configurations are the same for the 40 pin PDIP for all manufacturers and the component values are nearly the same for all Manufacturers.The same thing occurs when searching the ICL7136MAXIMhttps://www.analog.com/media/en/technical-documentation/data-sheets/ICL7136.pdfNon-multiplexRENESAShttps://www.renesas.com/us/en/document/dst/icl7136-datasheetMultiplexedAgain both have the same pin configuration and similar component values.Google hasn't helped to identify what's what.What's the difference between non-multiplex and multiplex LCDs and which do I have on this meter?

author: asis
author_rank: Frequent Contributor
timestamp: June 16, 2023, 06:31:35 am
content: Hi,It seems to me that by multiplexing we are talking about dynamic LCD indication, as can be seen on the example of the Xerox 600T1616 DMM circuit.As you can see, the MITEL MD4330B shift register is used.In your case, you can use ICL7136 because it works with LCD and can replace ICL7106.https://www.renesas.com/us/en/products/analog-products/data-converters/analog-digital-converters-adc-precision/integrating-display-output-ad-converters/icl7136-3-12-digit-lcdled-low-power-display-ad-converters-overrange-recovery?utm_source=supplyframe&utm_medium=SEP#overview

author: Greybeard
author_rank: Frequent Contributor
timestamp: June 16, 2023, 08:06:51 am
content: For my understanding it's a non-multiplexed LCD (every single segment has its own pin for contacting).

author: Jwillis
author_rank: Super Contributor
timestamp: June 16, 2023, 12:53:03 pm
content: Quote from: asis on June 16, 2023, 06:31:35 amYes the ICL7136 does look like a viable replacement for the ICL7106. I will have to give that a try as well.Quote from: Greybeard on June 16, 2023, 08:06:51 amI think I'm beginning to understand this now. Through stumbling around I found this. Where Dave Jones referred to it as Static.What still remains is to Why 3 out of the 4 manufacturers say the ICL7106 has Multiplex drive when they are in fact it has Non-multiplex(Static) drive.
Multiple faults Commodore 64 repair - Page 1
Forum section: electronics / repair

author: Shock
author_rank: Super Contributor
timestamp: December 29, 2019, 06:09:56 am
content: Interesting video showing half a dozen faults repaired on the same PCB.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 29, 2019, 06:19:15 am
content: I watched this yesterday. Painful.
MX Keys Led Driver / No Backlight / IC Identification  - Page 1
Forum section: electronics / repair

author: Kamynsky
author_rank: Newbie
timestamp: February 22, 2023, 08:47:55 pm
content: Hi EeverybodyI'm working on fixing Logi(tech) Mx Keys ,There is no back light on the keyboard .I have measured Voltage going to LED's , 3,5V from "motherboard"I have checked Led's there are starting to light up at 20V , all of them light up when I've checked them with DMM one by oneMy guess is that Led Driver have failed , but I'm unable to find Data Sheet for it any where (I guess I suck at searching for IC's)Led Driver ? is SOT23-6 with designation W0122 3508A on the IC (Photo below)Would appreciate help with identification , and maybe some ideas how to check if the issue is with the Led Driverhttps://imgur.com/a/nL0NxKs

author: fzabkar
author_rank: Super Contributor
timestamp: February 23, 2023, 06:59:27 pm
content: I expect that "508" is the date code (week 08 of 2005). Diode D4 has a date code of 0526.It might help if you could trace the circuit around this IC, and measure the voltages on each pin.

author: Kamynsky
author_rank: Newbie
timestamp: February 23, 2023, 07:44:33 pm
content: I found the ICIt is IS31BL3508Ahttps://www.lumissil.com/assets/pdf/core/IS31BL3508A_DS.pdf1.0MHZ BOOST CONVERTER WITH 38V INTERNAL MOSFET SWITCHUnfortunately this IC is not available in my country and shipping from mouser makes no sense (cost more than keyboard I'm trying to fix)I have found fallowing IC which seems to be good replacement for the original one AP3031KTR-G1https://media.digikey.com/pdf/Data%20Sheets/Diodes%20PDFs/AP3031.pdfCan some one please let me know if AP3031 will workpretty please !

author: fzabkar
author_rank: Super Contributor
timestamp: February 23, 2023, 08:05:18 pm
content: The feedback voltage (FB) for the BCD part is 200mV, whereas the IS31BL3508A has an FB of 300mV.If you measure the resistance between FB and ground, you should be able to work out the LED current (I = Vfb / Rfb). Then you could replace Rfb with Rfb x 2/3, or add a second resistor with a value of 2 x Rfb in parallel, to get the same current with the BCD part. The dimming function might need closer examination, though.You should check the ENable pin to confirm that the chip is being turned on.

author: Kamynsky
author_rank: Newbie
timestamp: February 24, 2023, 09:09:30 am
content: Thank you ,Will search a little bit more for more similar IC ,Will check all lines with Oscilloscope since now I know what they are doing and what I should see on them (time to learn using Oscilloscope)Once I have it running , will post what IC I've used and what had to do since this is quiet popular issue with this keyboard, maybe some one will use this knowledge
MX675 multimeter failed - Page 1
Forum section: electronics / repair

author: boumboauto
author_rank: Contributor
timestamp: December 13, 2023, 08:15:41 pm
content: Hello,I got a multimeter from the garbage because it's not working at all. In current and voltage modes it reads 0.00 all the time.In resistance/continuity mode it can read either 0 and beep when shorting the leads, or OL and beep when leads are disconnected. It's not capable of reading resistances values.In temperature mode it reads 552C and seems to be maxed out.Backlight and Display buttons seems functionalMin/max and Hold are hard to tell because it can't measure something so it's hard to hold a value...I started to open it : it has a board with many op/amps and the hand selector. This board has 12 pins connected to the "motherboard" tasked with display and buttons.I don't really know where to start as this is very complex, but I have in order of ideas :- Bulid a schematic as I move and check things up, it will not be complete but help me understand/troubleshoot.- Check input MOV and protection resistors- Checking power supplies starting from the battery, to the opamp power supplies, to the microcontroller in order to find if all the 5V rails, 3.3V 1.8V are all "normal"There is no fuse that I found on the inputs.
MXA CPU Bios Database  - Page 1
Forum section: electronics / repair

author: thorswait
author_rank: Contributor
timestamp: March 28, 2023, 07:28:45 pm
content: Hi all,I've recently purchase an MXA N9020A, the unit is based on windows XP with a PC2 32 bits. I was looking for an update cpu I request a quote from keysight (just for fun) 10K$ for a cpu upgrade ... It's kind of sad because when this PC is gone the unit would need to be scrap ... or being indecently pricy to repair ... Cheaper solution would be to find a way to use off the shelf Com Express PC.I did find out that the PC2 Embedded is from Kontron ComExpress board Type 2 with a special Bios. I did try with several Embedded PC each time it is recognized as a PCSERNO, with a serial number from the licence key. It's unable to identify the unit as a spectrum analyzer. I would like to make these unit more repairable and I was wondering if we can mod stock PC unit to upgrade at lower cost and keep the serial number and unit Model. The other way would be to regenerate the licence key but the keys seems to be different from the PNA/ESA version 16 char instead of 12 ...So far I have the Bios dump of a PC2 T2500 32bit and PC4 I7-L620 64bit Agilent Options. If anyone could help with the bios or continue the bios collection, feel free to share.
My GPS mysteriously brick itself  - Page 1
Forum section: electronics / repair

author: phred01
author_rank: Contributor
timestamp: September 24, 2023, 10:02:48 am
content: G'day allPlease helpMy Chinese made Win CE 6.0 GPS has stopped loading the OS. The unit is a Mediatek which has been work for 3 yrs The error message is PMP.exe is missing cannot cancel the Error message as the screen is not responding to cancell the window message. Tried to connect via the USB port but win 7 on my laptop reports the GPS is not recognized Another GPS unit has no problem connecting via the USBNeed to restore Win CE 6.0 to unbrick the unit

author: p.larner
author_rank: Frequent Contributor
timestamp: September 24, 2023, 03:22:04 pm
content: dont know if it helps but i had a uhappy chinese phabblet phone,about every 6 months it would do tjhe same,had to reflash the rom every time,that was a mediatek chipset too,in the end i smashed it to bits after about the 5th time it did it,it was random,sometimes ok for 3 months other times 3 days!.hope there nuclear reactors are better!.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 25, 2023, 02:28:20 am
content: not being rude, i dont think youll ever get e unless you buy an identical one and grab if possible the filesmaybe the memory is corrupt, WinCe on many device self extract in the memory before running

author: amyk
author_rank: Super Contributor
timestamp: September 25, 2023, 01:39:08 pm
content: Corrupted flash is common in cheaper devices that usually weren't built with good flash anyway.Will need more info on the device and what's inside; you may be able to find compatible firmware online as many of these are based on the same reference design.

author: phred01
author_rank: Contributor
timestamp: September 26, 2023, 05:35:36 am
content: Yes have another similar unit and have image of the GPS software. The main issue is the winCE os thats corrupted Wonder if there is a method to reinstall the winCE With Android boxes an update is achieved by inserting a sd flash with a upgrade file. So it there file for winCE OS?

author: coromonadalix
author_rank: Super Contributor
timestamp: September 26, 2023, 02:14:59 pm
content: i think you need to read about mce you will learn how it worknormally wince 6 work with a compressed file named nk.bin or elseon different companies they loved changing the bin extension file or simply renaming it to confuse peoplesome companies had flashing tool(s)you need to find what works in your unit ... and usb flash can or could work, BUT it depends on how the companies implemented thatif you have corruption, it get from somewhere in your unit ...nowadays working with WinCe is a pain in the ......... you need development tools, platform tools etc ...you need to find Mediatek tools / flash tools etc ....
My SONY DAV-HDX275 DVD Home Theatre System isn't turning on - Page 1
Forum section: electronics / repair

author: FallenHero02
author_rank: Contributor
timestamp: October 29, 2020, 10:27:44 am
content: I have a SONY DAV-HDX275 DVD Home Theatre System that keeps breaking when I try to fix it.We've had this sound system for many years without any issues but only recently did it "die" for some reason. Upon later inspection, I found that the fuse blew.The fuse that it was using was a 6.3A 250V fuse. I was able to acquire one and then replace it. It worked after that when I turned it on straight after putting the fuse in. After this, I didn't use it for a few weeks. When I did get to use it, it worked. But then about a week later I went to use it again and it didn't turn on again.I believe that it is once again the fuse but I do not understand why the fuse blew again.Can someone please help me find out what the problem is so I can fix it?

author: bob91343
author_rank: Super Contributor
timestamp: October 29, 2020, 06:19:57 pm
content: Obviously there is an overcurrent somewhere. First, replace the fuse and then measure the current through it. If it's safe, then you have an intermittent problem. If it's marginally close to rating, then you need to find out why.The problem is likely in one of two places. The power supply or one of the output amplifiers. Once you decide which, it should tell you where to look.

author: SpecialK
author_rank: Regular Contributor
timestamp: October 30, 2020, 02:28:22 am
content: Well let's see what we know. It's a tiny revice for being a 5-disc DVD player plus having six amplifier channels. So it's a switch-mode power supply because clearly it doesn't have enough iron (large transformer) for a properly sized linear power supply.Now according to the service manual available on-line, there are several devices I am suspicious of in the power supply:C901 Mylar capacitor across AC line. Assume for noise suppression or PFC.TH901 Thermistor to limit in-rush current. Seems like this is an issue.C903 main supply filter capacitor. These are often killed by the severe ripple currents in SMPS.VDR901 varistor for AC line regulation
My TDS going to die ? - Page 1
Forum section: electronics / repair

author: f14
author_rank: Regular Contributor
timestamp: February 17, 2022, 08:13:45 am
content: Hi guysMy tds3034b had flicker boot screen. after that. it still working fine . compensate passso what is my problems. thank you!

author: Teichhermelin
author_rank: Regular Contributor
timestamp: February 17, 2022, 08:19:27 am
content: This is due to illegal unlocking...Seriously I think a new display is due.

author: f14
author_rank: Regular Contributor
timestamp: February 17, 2022, 08:24:10 am
content: yeah. I had "upgrade" it to 600mhz. but I back to stock 300mhz few year ago because it not pass 600mhz scope. still pass 300mhz when I send it to calibationthis problems I just got some days ago .screen I think it fine .

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 17, 2022, 05:59:31 pm
content: Could be LCD itself or video IC / RAM on mainboard.SPC has nothing to do with it.

author: Runco990
author_rank: Frequent Contributor
timestamp: February 17, 2022, 11:33:43 pm
content: Sometimes it's just the display ribbon cable needs a re-seat.
Myryad MA240 power amp pops when shutting down.  - Page 1
Forum section: electronics / repair

author: Perrin21
author_rank: Regular Contributor
timestamp: March 09, 2020, 01:29:56 am
content: hi, I have 4x myryad MA240 Amplifiers (running bridged as monoblocs) and one has started to pop when the relay shuts off as its powered down. the other 3 amps don't and this is a new issue for the one that does. Any ideas what is causing it? could it be the relay is worn and needs replacing? or could it be something else? otherwise it works fine. I've checked for DC on the terminals and there's nothing.

author: David Hess
author_rank: Super Contributor
timestamp: March 09, 2020, 02:15:15 am
content: If it has a relay in series with the output, then that could mean that a DC offset has developed for whatever reason.

author: Renate
author_rank: Super Contributor
timestamp: March 12, 2020, 03:40:31 pm
content: I would suspect that the DC is crashing too quickly for the protect circuit to kick in.Since you have a bunch of these things, it should be easy to compare.Put your scope on single sweep and watch the collapse of the DC power supplies when you shut it off.If the supplies are bipolar a big difference between plus and minus could certainly cause problems.I would suspect that the electrolytics on the bad unit are low in value.
Mystery capacitor "UA 2.2µF" [SOLVED] - Page 1
Forum section: electronics / repair

author: klausman
author_rank: Regular Contributor
timestamp: August 27, 2025, 02:52:31 pm
content: I am working on a Luxman L-525 hifi amplifier and I noticed these unusual-looking capacitors (C452a/b):The service manual lists them simply as "UA 2.2µF", no voltage or anything else given. As far as I can tell, these are U-con UA capacitors from the mid-late 80s. They seem to be fine, but I wondered what kind of capacitor technology they are, what their purpose is, and if I did have to replace them, how to go about that.Here's part of the schematic, C452a is at the top left:

author: wraper
author_rank: Unknown
timestamp: August 27, 2025, 03:05:10 pm
content: They are film capacitors, rated for 200V (2D), most likely polyester.

author: Grandchuck
author_rank: Super Contributor
timestamp: August 27, 2025, 03:09:20 pm
content: Mylar? only a guess

author: Zero999
author_rank: Super Contributor
timestamp: August 27, 2025, 03:12:22 pm
content: ProbablyBoPET(Mylar) filmhttps://www.amazon.co.uk/Capacitor-2A474J-Polyester-capacitor-BIANMTSW/dp/B0F2HCHR3BThey're quite a common type of capacitor, but perhaps 200V at 2.2µF is less so, because makes them big.They should last forever as long as they're used within their ratings.
mystery OP-AMP - Page 1
Forum section: electronics / repair

author: Teach
author_rank: Newbie
timestamp: October 11, 2020, 05:33:21 am
content: I'm repairing a dead Tektronix FG501 Function Generator. sn B060534Turns out ALL thirteen OP-AMPs were non functional.I replaced all with 741's and It is working nicely that was easy.Now my question -----The "op-amps" in the unit were marked (Old National Semiconductor LOGO) followed by 241....at the top.SL in the middle of the chip.60466 at the bottom.Large letters FVFVFV printed on the underside.That's right, 241 ! not 741....I searched for days.....What could this be ? Fakes installed by previous repair attempt? A part so obsolete it dis-appeared from the internet ?!!Anyone that can help Identify it. Thank You !!!

author: magic
author_rank: Super Contributor
timestamp: October 11, 2020, 05:50:58 am
content: Prolly a custom Tek part number, see if you can find service manual.LM341 was a three terminal voltage regulator, LM241 would have been an industrial temperature version of that. Surely none of that.Teardown of the carcasses would reveal what they were.

author: Teach
author_rank: Newbie
timestamp: October 11, 2020, 06:42:30 am
content: Magic, go to the head of the class-------------- You are CORRECT !!!I do have the manual, and it does indicate a Tek manufacture part number................ 156-0067-06Well DANG searched it up and It is indeed a 741.Figured that by looking at the Pin-Out in the schematic.Mystery solved.Unit running smooth !!!Thank You Magic !!! (P.S. all the 741's in my Tek power supply were dead too(working fine now also))OLD OP-AMPS Hmmmm.

author: fzabkar
author_rank: Super Contributor
timestamp: October 11, 2020, 08:28:55 pm
content: You can often find an equivalent to the manufacturer's number at NTE Inc:https://www.nteinc.com/search.phphttp://www.nteinc.com/specs/900to999/pdf/nte941m.pdfYou can find old databooks here:https://mirrorservice.org/sites/www.bitsavers.org/components/national/_dataBooks/

author: David Hess
author_rank: Super Contributor
timestamp: October 11, 2020, 11:05:05 pm
content: The 156-0067-06 was selected for a +/-20 Volt supply voltage. Originally these were all suppose to be from Motorola, RCA, or Texas Instruments so I wonder if they were replaced at some point. Or maybe Tektronix got National to grade them for +/-20 volt operation and that is why the part number is weird.They should be replaced with 44 volt parts like the 741, 741A, or 741M but *not* the commercial 741C which is only a 36 volt part.
mystery resistor type and value ? - Page 1
Forum section: electronics / repair

author: ijchan223
author_rank: Contributor
timestamp: February 28, 2021, 04:54:13 pm
content: hi, i am working on repairing a old inverter welder that they no longer sell replacement parts for.i need help identifying the resistor . my cheap multimeter hunts but eventually stops on 25 ohm after 20 seconds. but it is marked as 12p, is there a conversion chart for the value? i would expect it to be 12 ohms.it appears to be some trickle charge for the large DC caps i made some drawing on paint does it make sense for both r17 and 16 to be populated with a resistor?https://photos.app.goo.gl/n5KKZuBp6c9qJ1pP8

author: George Edmonds
author_rank: Frequent Contributor
timestamp: February 28, 2021, 05:15:01 pm
content: HiIt looks like an NTC device, these are used to limit the switch on surge current, the have a few tens of Ohms resistance when cold, but drop rapidly in resistance when they get hot.George G6HIG

author: ijchan223
author_rank: Contributor
timestamp: March 01, 2021, 12:09:30 am
content: thanks, that is exactly what it is, and the circuit is working correctly. My cheap at home meter wouldn't read anything 12vDC correctly.Looks like the issue is on the control side.
N1201SA antenna analyser failure - Page 1
Forum section: electronics / repair

author: okz00k
author_rank: Newbie
timestamp: December 29, 2018, 07:04:44 am
content: A little over 1 year ago I purchased my favourite tool - a N2101SA vector impedance analyzer. Its a pocket size device which does just about everything I have ever wanted for tuning the VHF and UHF antennas I build and checking resonance of commercial antennas I use. I love this device. When it is working properly it gives me great graphical view of antenna resonance over the frequency ranges I'm interested in. Below are a couple of pics when it was working.

author: okz00k
author_rank: Newbie
timestamp: December 29, 2018, 07:20:03 am
content: After three months in the drawer the battery was low and it would not turn on. After charging the battery, now the device just provides a messy response, with no resemblance of the antenna connected to its SMA connector. It now displays dips and peaks a few MHz apart, continuously across the entire spectrum. Display is the same if a 50ohm dummy load is connected or if the antenna connector is left open circuit, although the position of some peaks change when the dummy load is attached.I have reset the device without effect. Battery voltage is 4.13vI purchased the device from Banggood and they will not accept a warranty return after 12 months. I cannot find contact details of the manufacturer AAI (Accuracy Agility Instruments) Any thoughts on how I might restore the proper operation of this device will be greatly appreciated.

author: RCinFLA
author_rank: Contributor
timestamp: October 25, 2019, 05:10:51 pm
content: Schematic made from photo of PCB

author: mikerj
author_rank: Super Contributor
timestamp: October 25, 2019, 07:13:45 pm
content: Do you have a 50R dummy load to try it with? I'm wondering if it managed to corrupt it's calibration when the battery died, theinstructionshave a section about what to do when it completely locks up, so seems like they expected that to happenThe instructions also have details of calibrating the device, though I would advise dumping the serial flash device that holds the cal data before you do that. One of the many cheap programmers should handle that if you have one.Looks like a very neat little tool (when it's working!).

author: okz00k
author_rank: Newbie
timestamp: October 25, 2019, 11:24:29 pm
content: Problem solved. The device simply needed to be re-calibrated. I selected the Calibration option from the menu and followed the prompts. For calibration you need:- open circuit- short circuit, and- 50 ohm dummy load.I'm so pleased to have my N1201SA working again.

author: izmile
author_rank: Newbie
timestamp: March 04, 2022, 06:29:44 pm
content: Old post.. but might be useful for someone in future.I had the exact same issue and found that U4 (3V3 linear regulator) was faulty. Replaced it and it works fine.
N1911A display issues  - Page 1
Forum section: electronics / repair

author: grendle373
author_rank: Contributor
timestamp: May 28, 2025, 03:08:44 pm
content: Sorry asked this in the wrong forum :Having some issues with a N1911A power meter i was gifted. The unit powers up and responds over gpib, supply voltages look good. The display flashes the splash screen on power up then goes white. I had a replacement display from another unit but it does the same. I resoldered the front panel cable connector and don't see anything obvious. I've seen similiar units have bad fpga's but those usually just wont boot at all. Is there a display driver chip that possibly fails? Anyone had luck with these? All help is appreciated. Thanks!
SMD marking help: N2P3D - Page 1
Forum section: electronics / repair

author: PKTKS
author_rank: Super Contributor
timestamp: September 12, 2021, 10:55:01 am
content: What piece may be equivalent to N2P3D ?Magic smoke. Trace recovered by 000 fuse.ThanksPaul

author: wraper
author_rank: Unknown
timestamp: September 12, 2021, 11:02:54 am
content: Looks like Si2302CDS MOSFEThttp://www.s-manuals.com/pdf/datasheet/s/i/si2302cds_rd_vishay.pdf
N5320A / PNA-L (or E8361A, E8362B, E8363B, E8364B) HDD image for recovery - Page 1
Forum section: electronics / repair

author: techfreakz
author_rank: Newbie
timestamp: January 29, 2024, 11:48:49 pm
content: Hello,It isn't quite "HP" era, but I'm hoping I still qualify to join the "gentlemen with vintage hp kit" club.....I'm trying to resurrect an N5320A 20GHz 4-port PNA-L.The HDD is partially corrupted (including the Ghost recovery image in the fourth partition) and some of the recovery tools on the third partition (including "pna.msi....sighhh"), which leaves me in a bit of a pickle!Does anyone have an image of the HDD (including all four partitions) from that era?I believe the instrument had firmware A.07.50.48 installed. An upgrade to A.07.50.67 would be nice, but beggars can't be choosers.Looking at the recovery scripts, it looks like they may have been fairly generic and so an image of a E8361A, E8362B, E8363B, E8364B, "PNA" HDD might suffice for installation on a "PNA-L".Any assistance would be very much appreciated and will be repaid in goodwill and expensive whisky!Best regards,Alex
N6705 getting stuck while startup!!! - Page 1
Forum section: electronics / repair

author: wick91274
author_rank: Newbie
timestamp: January 08, 2024, 05:57:41 am
content: we have an 10 years old keysight n6705 power analyzer, one day, it getting stuck while startup after pressing any key also it doesn't respond looking for suggestion what will be the issue?
N9000A adjustment - Page 1
Forum section: electronics / repair

author: Drirr
author_rank: Regular Contributor
timestamp: February 20, 2020, 06:40:03 pm
content: HiI would like to ask you if there is any way to adjust flatness of CXA N9000A? Unit is "after repair"I noticed that there is N7800A software which should be for "adjustmen" I guess? But Im not able to make it work without license.ThanksDavid

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 20, 2020, 06:52:28 pm
content: Apart from the license you need some specific equipment to be able to use the calibration software and that has been a showstopper for me.Have a look here:https://cal.software.keysight.com/MXA/Help/Content/testequip.htm

author: Drirr
author_rank: Regular Contributor
timestamp: February 20, 2020, 07:06:29 pm
content: @ PA0PBZ thanks for reply,This mean that I need exact type of .. for example generator to adjust flatness?What I have in here is complete calibrated HP RF lab upto 26.5GHz ( 83630 generators, analyzers, scalar, vector) there is still no possibility?

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 20, 2020, 07:19:50 pm
content: Please check the link and see the Recommended and Alternative model columns for each function.For instance, I see 2 x E9304A Option H18 mentioned for CXA adjustment and performance testing, and if you don't have those my guess is that you will have a problem. Note that it's just a guess and not a fact, but you see where I'm going. If this is a one-off I'd personally find a company that can do it for you, less headache and probably a lot cheaper.
N9320A Service Password & Manual - Page 1
Forum section: electronics / repair

author: Tony_G
author_rank: Super Contributor
timestamp: March 17, 2025, 05:23:02 pm
content: Hey All,I dumpster dove one of these spectrum analyzers - It seems a little off and the keyboard really needs a cleaning.Does anyone either have or have a pointer to:The N9320A Service ManualAny N9320A CLIPSThe "Service" menu passwordThe machine seems to basically work (well apart from grime, keypad and a weird ref out issue) so any help appreciated.Thanks,TonyG
Nad 214 amplifier pulling to much current? - Page 1
Forum section: electronics / repair

author: reddish75
author_rank: Regular Contributor
timestamp: September 25, 2023, 03:29:21 pm
content: So I've recapped this Nad 214 amplifier and when I switch on with both amplifier boards disconnected it pulls enough current for a 150w to be lit ( not brightly ) could this be classed as normal? Please see attachment for pics and psu schematic

author: Swake
author_rank: Frequent Contributor
timestamp: September 25, 2023, 04:27:19 pm
content: it is a lot but my sub sucks 80W before music, and that amp is a single channel.

author: shakalnokturn
author_rank: Super Contributor
timestamp: September 26, 2023, 11:51:56 pm
content: "Not brightly" isn't saying that much, it could be normal, a current measurement would tell us more.Recapping is great, being a NAD I'm sure it had plenty of dry solders did you look out for those?Have you checked the qiescie't current is as specified?

author: TimFox
author_rank: Super Contributor
timestamp: September 27, 2023, 12:13:19 am
content: I could not find an actual specification, but a post elsewhere about adjusting the NAD 214 bias current indicated that the quiescent power consumption (from mains) was between 30 and 50 watts (no signal).
NAD 3140 phono input mistake !! - Page 1
Forum section: electronics / repair

author: guizmo1967
author_rank: Regular Contributor
timestamp: September 21, 2024, 01:09:44 am
content: Hello,I accidently connected my aux input (TV) to phono1 and now phono1 is louder (volume higher than phono2).If I don't touch the volume knob and switch my turntable to phono2, the sound is very good on both but phono2 is just lower than phono1Do you have any idea why ??I look at the service manual and there is two 330K resistors connected to ground and to each phono inputs. Do you think that could be one of those resistors ?

author: guizmo1967
author_rank: Regular Contributor
timestamp: September 21, 2024, 01:32:31 am
content: UPDATE !!!I just read the Owner's manual and phono 1 and phono 2 has different output level, so nothing wrong with my amp !

author: helius
author_rank: Super Contributor
timestamp: September 21, 2024, 02:06:16 am
content: Hi-Fi amplifiers from decades ago often had selectors for different phono signal levels. That was because the output from a turntable depends on the cartridge design: moving magnet (MM) cartridges have much hotter outputs compared to moving coil (MC) designs. To provide a useful volume range, the preamplifier needs to use correspondingly different gain for these types.Plugging a line-level output into a phono jack is a pretty bad idea, though. Line level can vary but in the worst case it can be over a volt, whereas a MC input expects a 250 microvolt signal. A MC input may also have a rather delicate transformer attached, and it could have been negatively affected.
NAD 3140 - regulated power supply - solved - Page 1
Forum section: electronics / repair

author: willb
author_rank: Regular Contributor
timestamp: November 20, 2024, 06:57:09 pm
content: Good day all!I have been chasing my tail for 2 days over this issue and can't seem to get anywhere.Basically, the positive rails in the power supply are good but the regulated negative side is no good. All the semi-conductors test OK out of circuit in my DCA75 tester. I replaced the few electro caps, no difference. All the resistors are good. I have attached a photo of the schematic with the voltages I have in red at the measured point. I am at a loss.Any insight would be greatly appreciated!Cheers!

author: Messtechniker
author_rank: Frequent Contributor
timestamp: November 20, 2024, 08:15:29 pm
content: Quote from: willb on November 20, 2024, 06:57:09 pmAccording to your measurements that BD 140 with both collector and emitter voltages at at 55 V shoud be dead.If on a heat sink, bad isolation could be shorting out this BD 140.

author: willb
author_rank: Regular Contributor
timestamp: November 20, 2024, 10:52:46 pm
content: it's fixed.Someone was in here before me, replaced Q808 but installed it backwards, swapping the emitter and the base.
NAD 317 Burnt Diode on inputboard  - Page 1
Forum section: electronics / repair

author: Cowdangerous
author_rank: Newbie
timestamp: April 02, 2024, 05:46:28 pm
content: Hello all,I bought a NAD 317 recently and i opened it up for a visual inspection. Here i found Diode 657 and 658 on the inputboard, looking like they are burnt. So i traced them in de service manual to what i think is the input protection? I am a newby in electronic repairs but i would like to make it a hobby. Can anyone help me with what this is, where it is for and what i need to replace? Is there anything else i should check while i replace these diodes?The amp is working fine so far and i think it sounds great. I've tested it with my turntable (which sounded really bass heavy), bluetooth and direct connection on my phone.Thanks in advance!

author: Gyro
author_rank: Super Contributor
timestamp: April 02, 2024, 07:03:11 pm
content: Welcome.Those are series Zener diodes to drop those +/- 52V rails down to something that the 24V regulators can safely digest. They most likely run warm, they look fine. As long as they don't read dead short then they are fine (if they were shorted, the regulators would have blown up by now).

author: Cowdangerous
author_rank: Newbie
timestamp: April 02, 2024, 07:14:45 pm
content: Hi,Thank you very much for your reply! They indeed do run warm! Measured around 50 degrees Celsius while the rest stayed around 30.

author: Gyro
author_rank: Super Contributor
timestamp: April 02, 2024, 07:21:00 pm
content: Yes, they're fine then. They're perfectly happy at 50'C.