Author Topic: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621  (Read 35999 times)

0 Members and 1 Guest are viewing this topic.

Offline chihaxinh

  • Regular Contributor
  • *
  • Posts: 126
  • Country: vn
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #25 on: February 06, 2016, 01:56:39 pm »
Hi Tin

Ok let's me check all zenner and report for you soon !

Update: I check all zenner have voltage drop like datasheet, but CR201A (  4.7V ) in Ohm current source have osic from -0.9V to 1.4V .

And voltage drop on pin 7 U201-B have only 4.6xxV

« Last Edit: February 06, 2016, 02:35:01 pm by chihaxinh »
 

Offline robjpiel

  • Newbie
  • Posts: 4
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #26 on: November 28, 2016, 06:43:10 am »
I have been working along with this thread trying to solve a similar issue that I have with my 34401a. 

Error codes only:
612 Ohms source current failed,
618  DC HV attenuator failed (no surprise here- I hit it with between 1100~1250VDC while in the DCV AutoRange, yes this was dumb but we got a new 34461 and now I'm trying to repair this 34401 for fun/learning experience/I want it for myself)

Sorry to dredge up such an old thread but it has so much relevant information in it, and you all seem to be the only resource I could find out there with this kind of information.

The meter does work in several other functions such as the DCV all except the 100V and 1kV range so I figure it is worth some time and attention.  When it is in these two fried ranges it is not accurate at all on low V inputs and only registering 70% of actual higher up ie. a 1000 volt input will only read 700v.  (It will not accept a new calibration this far out fyi- I tried this first)

I first thought I blew up the 9.9M and 100k ohm voltage divider resistors in u102-A, but they are fine so I checked all the rest in:
u102-C: 2k, 2k 2k-All Good
u102-D: 20.57k, 5k, 50k, 500k, 1M-All Good.

I checked all the voltages that I could (attached).  I highlighted red only values with significant deviation from what the OP had (Zucca I believe) and in black I have additional readings in case they were to help me down the road, but most of my values turned out to correlate with TiN's working meter leading me to think this IC u102 may be OK??  Hoping anyway.  Where my confidence stops is after checking u102-B I get 2k Ohm (pin11-14), 17.3k (13-14), and 84.8k (13-15)instead of 2k, 18k, and 180k.  But I didn't really expect any values to be in tolerance since its still in the circuit and I'm measuring resistance which I know is fundamentally wrong to begin with.

The second issue I found here is that my output Ohms Current test did actually have 0 current from the low terminal to the anode of CR202.   I was measuring with a 77IV so I will try it again to confirm with a 3458 tomorrow I guess just to be sure. 

If anyone would like to call me an idiot for looking where I have been,  and point me in the right direction that's obvious to you that would be much appreciated, or tell me those resistance readings in u102-B are OK since they are still in the circuit that would be cool too.  Otherwise my next step was going to be to see if RV102 was having an issue only when it sees higher voltages and maybe the rest of the meter is working just fine after that point - but I will say I dont know how to check a -"Diode-Varistor 1.1kV" yet.   Time to pull out my textbook I guess.

Thanks in advance for any input you may have!!!   





 

Offline Dr. Frank

  • Super Contributor
  • ***
  • Posts: 2377
  • Country: de
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #27 on: November 28, 2016, 10:03:50 am »

618  DC HV attenuator failed (no surprise here- I hit it with between 1100~1250VDC while in the DCV AutoRange, yes this was dumb ...

I don't understand this expression..
What exactly happened?  Did you apply 1250Vdc when in Ohm mode, or simply when in DCV / Auto mode?
The instrument should withstand such overvoltages to some degree in both modes.
 

The meter does work in several other functions such as the DCV all except the 100V and 1kV range so I figure it is worth some time and attention.  When it is in these two fried ranges it is not accurate at all on low V inputs and only registering 70% of actual higher up ie. a 1000 volt input will only read 700v.  (It will not accept a new calibration this far out fyi- I tried this first)

Are 10Vdc, 1Vdc, 100mVdc accurate?
I would have expected that you damaged these lower ranges by applying the overvoltage..

Anyhow, the overvoltage might have damaged the input path, somewhere in between the input jack, ESD circuit, relays K101, L101, K104 , towards  U102-A, that is the 100:1 divider.
I propose that you chose 1000V DC range, apply 10V to the input jacks, and measure with your 34361 in high Z mode at first the input voltage to U102-A, i.e. pin 1.
If you don't see 10V, you have to check the components and PCB traces of the mentioned input path.
If 10V are present on the input, check pin12, if the divided 100mV are correct. If not, the input multiplexer, pin 8 of U101-B may have been damaged.

I first thought I blew up the 9.9M and 100k ohm voltage divider resistors in u102-A, but they are fine so I checked all the rest in:
u102-C: 2k, 2k 2k-All Good
u102-D: 20.57k, 5k, 50k, 500k, 1M-All Good.

I assume, that you unsoldered U102, before making these measurements?

I checked all the voltages that I could (attached).  I highlighted red only values with significant deviation from what the OP had (Zucca I believe) and in black I have additional readings in case they were to help me down the road, but most of my values turned out to correlate with TiN's working meter leading me to think this IC u102 may be OK??  Hoping anyway.  Where my confidence stops is after checking u102-B I get 2k Ohm (pin11-14), 17.3k (13-14), and 84.8k (13-15)instead of 2k, 18k, and 180k.  But I didn't really expect any values to be in tolerance since its still in the circuit and I'm measuring resistance which I know is fundamentally wrong to begin with.

Correct, you will only get the proper values by unsolder U102...

Very probably, U201-B is damaged, pushing current from its + input into the node between Q201 and pin4 of U102-D.
This low bias OpAmp in many cases already, fails after years, or maybe the overvoltage killed it, as the 100:1 divider is sitting in the same package U102.
Anyhow, replacing U201 probably will solve this problem.




The second issue I found here is that my output Ohms Current test did actually have 0 current  from the low terminal to the anode of CR202.   I was measuring with a 77IV so I will try it again to confirm with a 3458 tomorrow I guess just to be sure. 


That may also be caused by a failed U201-B

Frank
 
The following users thanked this post: robjpiel

Offline robjpiel

  • Newbie
  • Posts: 4
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #28 on: December 02, 2016, 04:36:31 pm »
Thank you Dr. Frank,

Yes- To cause the problem I applied 1250VDC to the meter while in DCV Auto range.
(I was testing the 1KV output of insulation resistance testers (meggers), normally they only put out 1050vdc and when I tested a dozen of the new fluke 1507 they were putting out over 1200vdc and without thinking twice I had tested 8 in a row and then they started reading 800vdc.  Went back and checked the units that had just read 1250 and they too were reading 800vdc.  Verified the problem with my meter calibrator, and tried to recalibrate the 34401 with no luck.  Then I ran the self test and got the codes.)

Yes- the 10VDC, 1VDC and 100mVDC all are 100% accurate (0-full scale). 
-Every ACV range is 100% accurate as well. 
-Resistance ranges are all good until I get up to the 10MOhm range (which reads 9x higher than it should)

Believe it or not I actually did not de-solder the IC for any of these measurements.  I Do not have the equipment yet to do so.  I am ordering some soon so that I can enhance my repair capabilities to SMT and ics.  But while I had it open I probed it anyway and all those resistance values were dead on until I got to u102-B.       As soon as I get some equipment to desolder this IC I will check u102 properly.

Current Output Over the Resistance Ranges  All check Good
100Ohm    1.010407mA/7.90V
1kOhm   1.010403mA/7.912V
10KOhm    100.71440uA/8.185V
100kOhm  10.09959uA/8.422V
1MOhm 5.060033uA/8.439V
10MOHM    0.505691uA/5.0719V
100MOhm  0.505714uA/4.820V

Below is what I have gotten so far for voltage readings going to the divider.  The voltage up to R122 is 10.000V after it drops to .8V  going into u102 pin 1 then then STEPS UP to 8V. ?  I feel that means R122 may be open?  I checked the Resistance across it (while in circuit) and it reads .22GOhm. 

I piggybacked a 6.19K decade resistor over R122 and This 100V and 1kV range all works fine.  (I'll need to recalibrate it when I get the replacement R122 installed) 

Excellent!! THANK YOU VERY MUCH FOR YOUR HELP SIR!

I'll post back after if it is not 100%


-Rob
 

Online Kleinstein

  • Super Contributor
  • ***
  • Posts: 14073
  • Country: de
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #29 on: December 02, 2016, 04:59:59 pm »
R122 might need to be a special resistor, e.g. fusible or higher peak voltage rating. If this resistor burnt, the root cause might have been arcing in the relays directly following it (e.g. during switching).

Trouble with high Ohms readings somewhat points to possible excessive leakage. So it might be a good idea to check that too (e.g. 1 to 10 M resistor across input in the 1 V or 100 mV range, alternatively observe charging of a small (e.g. 1 nF) low leakage cap).
 
The following users thanked this post: robjpiel

Offline robjpiel

  • Newbie
  • Posts: 4
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #30 on: December 02, 2016, 05:57:03 pm »
The two upper Ohm ranges are working now too, with me holding that substitute decade resistor in place of R122 it is surprisingly stable even with my shaky connection.

Thank you for the info.  If it does not stabilize and pass calibration I will definitely look into that.

You guys have been a big help
 

Offline Samogon

  • Frequent Contributor
  • **
  • Posts: 457
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #31 on: December 21, 2016, 04:07:31 pm »
R122 made my day. Another 34401A is back to work.
 

Offline robjpiel

  • Newbie
  • Posts: 4
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #32 on: December 21, 2016, 06:52:06 pm »
Just be sure to run through all the performance verification steps after.   Mine was out of tolerance across several ranges.   I just recalibrated all of them and this thing is working great.
 

Offline Samogon

  • Frequent Contributor
  • **
  • Posts: 457
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #33 on: December 21, 2016, 09:41:44 pm »
Sure it will be calibrated.
 

Offline Satbeginner

  • Regular Contributor
  • *
  • Posts: 151
  • Country: es
  • Dutch, early retired, living in Spain
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #34 on: June 22, 2017, 05:08:15 pm »
Hi all,

This thread now seems to be a 34401A repair source, so sorry for me joining as well:

I acquired a 34401A that has the following errors: 612,613,615,617,618,619 and 621.
Both DCV and ACV readings seem to be OK.

Based on the information here, I did some checks and it seems that the second half of u201 (b) has died.
The 7V on r201 and/or r202 when changing ranges is still there, so I ordered some ad706's.

Will keep you posted, in saludo,

Satbeginner (Leo)
You need a scope to repair a scope, and you need many multimeters to repair another multimeter!
*Tek 2467B, Tek 2465B, Tek 2465B, Tek 485, Tek 475A,  Keithley 175A, Keithley 2000, HP 3468B, HP 3457A, HP 34401A, PM 6671, PM 5716, Fluke 45, Fluke 75, Fluke 77, Fluke 79, AFX 9660BL, KPS 605D, etc. *
 

Offline Satbeginner

  • Regular Contributor
  • *
  • Posts: 151
  • Country: es
  • Dutch, early retired, living in Spain
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #35 on: June 28, 2017, 05:56:49 pm »
Hi all,

This thread now seems to be a 34401A repair source, so sorry for me joining as well:

I acquired a 34401A that has the following errors: 612,613,615,617,618,619 and 621.
Both DCV and ACV readings seem to be OK.

Based on the information here, I did some checks and it seems that the second half of u201 (b) has died.
The 7V on r201 and/or r202 when changing ranges is still there, so I ordered some ad706's.

Will keep you posted, in saludo,

Satbeginner (Leo)

Hi all,

Today the AD706's arrived, so I could replace U201.

Result?? Yes!! One 34401A back to life, and compared with my HP 3457A well within specs.

I am one happy bunny!

Un saludo,

Satbeginner (Leo)
« Last Edit: June 28, 2017, 07:02:56 pm by Satbeginner »
You need a scope to repair a scope, and you need many multimeters to repair another multimeter!
*Tek 2467B, Tek 2465B, Tek 2465B, Tek 485, Tek 475A,  Keithley 175A, Keithley 2000, HP 3468B, HP 3457A, HP 34401A, PM 6671, PM 5716, Fluke 45, Fluke 75, Fluke 77, Fluke 79, AFX 9660BL, KPS 605D, etc. *
 

Offline Samogon

  • Frequent Contributor
  • **
  • Posts: 457
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #36 on: June 28, 2017, 11:43:36 pm »
Good job!
Welcome to the club:)
 

Online ZuccaTopic starter

  • Supporter
  • ****
  • Posts: 4298
  • Country: it
  • EE meid in Itali
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #37 on: June 29, 2017, 07:51:55 am »
Satbeginner nice!

When I stared this I had not idea this failure was and is so popular... I have no clue why the U201 is dying so often...  meh... lesson learned always post a fix in the EEVBLOG to help the world.
« Last Edit: June 29, 2017, 08:42:51 am by zucca »
Can't know what you don't love. St. Augustine
Can't love what you don't know. Zucca
 
The following users thanked this post: Satbeginner

Offline HighVoltage

  • Super Contributor
  • ***
  • Posts: 5453
  • Country: de
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #38 on: June 29, 2017, 08:37:07 am »
I have replaced a few U201 already and when I get another broken 34401A, this is a first go to check for me now, right after testing the power rails.

With all the information on eevblog about the 34401A repair, it has gotten much easier to fix these great DMMs.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline Satbeginner

  • Regular Contributor
  • *
  • Posts: 151
  • Country: es
  • Dutch, early retired, living in Spain
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #39 on: June 29, 2017, 08:44:46 am »
I don't get it either, because the "A" half was still working fine. It must have something to do with somebody having applied a (really) high voltage while on ohms setting??

Un saludo a todo.
You need a scope to repair a scope, and you need many multimeters to repair another multimeter!
*Tek 2467B, Tek 2465B, Tek 2465B, Tek 485, Tek 475A,  Keithley 175A, Keithley 2000, HP 3468B, HP 3457A, HP 34401A, PM 6671, PM 5716, Fluke 45, Fluke 75, Fluke 77, Fluke 79, AFX 9660BL, KPS 605D, etc. *
 

Offline Andrejka

  • Contributor
  • Posts: 17
  • Country: lt
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #40 on: April 04, 2018, 04:22:43 am »
Hello colleagues

Can someone suggest me, what components to check if:
Self test shows errors: 612, 613, 615, 617, 618, 619, 621, 622
Ohm current source is working - I got correct 500nA,  5uA, 10uA, 100uA and 1mA
Only DCI mode seems to working correctly, on other modes only chaotic readings.
Comparing to other meter there is no input impedance (infinite input impedance reading). In working meter on DCV mode I can measure 10Mhom input impedance.

If Ohms current source is working then custom resistor assembly is ok?

Thanks

Andrej
 

Offline TAMHAN

  • Frequent Contributor
  • **
  • Posts: 407
  • Country: sk
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #41 on: April 04, 2018, 08:19:45 pm »
Likely one of the SMD inductors close to the input jacks. They, um "levitate away" during shipping and handling. Sadly, I lost mine...and getting that Gowanda part is difficult. Which is why I currently dont have a working 34401A...but it is very low on the repair priority list.
Feel like some additional tamile wisdom? Visit my YouTube channel -> https://www.youtube.com/user/MrTamhan for 10min tid-bits!
 

Offline Andrejka

  • Contributor
  • Posts: 17
  • Country: lt
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #42 on: April 05, 2018, 06:35:58 pm »
Likely one of the SMD inductors close to the input jacks. They, um "levitate away" during shipping and handling. Sadly, I lost mine...and getting that Gowanda part is difficult. Which is why I currently dont have a working 34401A...but it is very low on the repair priority list.

Tamhan You are 100% right - cracked small inductor. Absolutely invisible with naked eye, but signal path tracing helps. Now looking for suitable replacement...





Thanks

Andrej
 

Offline Resonant

  • Contributor
  • Posts: 13
  • Country: gb
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #43 on: May 06, 2018, 01:48:25 pm »
HP 34401a repair
I recently acquired a nice HP34401a, an early one made in the USA and I thought I would do some checks against my calibrated meter and left it on for a while, tried various voltages and they were close but generally a little high. This meter had been in private ownership and had very little use and probably not been calibrated since new.
After trying various voltages and putting the meter through its paces it came up with an error. So I re-ran the Test All which had passed OK earlier and it came back with the 612, 613, 615, 617, 618, 619 error codes. A quick scan on the net brought me to this thread where my heart sank when I read of all the possibilities and expense this could be.
I ran a few tests Voltages above 100V DC were Ok all AC ranges worked and there was still output current for the ohms readings although there were no readings. I tried the input impedance on most ranges it was the expected 10M ohm but on 100mV 1V and 10V it was only 66K so out with the circuit diagram of the input circuit.
It was late so I pondered it overnight and thought there must be a leak/short on the input. Looking at the resistor ladder R104 to R109 6X 13K  looked close to the value I was getting so I checked C100 470p and sure enough it measured 1 ohm, so I lifted one end and ran the self-test and it passed again all OK, so I will be ordering a cap and checking out the resistors. I will post again when completed. I assume the cap is a filter to remove noise on the input along with C101.
A request, I was intending to calibrate it but the manuals explanation makes it look complex compared with a Keithley 2000 which I have done previously I found after entering parameter step 5 pressing Auto/Man exited calibration, so how do you move on to the next value without exiting?
Chris
 

Offline HighVoltage

  • Super Contributor
  • ***
  • Posts: 5453
  • Country: de
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #44 on: May 06, 2018, 03:53:58 pm »
Nice that you found the problem.

Some 34401A also suffer from blown tantalum capacitors.
When I have repaired these DMM, I replaced all of them.

If you do manual calibration, you have to do it for each value separately.
There is no next "value"

There is one "shortcut". Instead of pressing SHIFT and MENU ON/OFF just press SHIFT RECALL and it brings you back to the calibration menu.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline Resonant

  • Contributor
  • Posts: 13
  • Country: gb
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #45 on: May 11, 2018, 06:49:24 pm »
Well its all fixed a replacement input cap from CPC (CA0708) and some Panasonic FR series 105C Caps for the PSU and all working properly again. I checked all the 13k input resistors to make sure they had not been stressed and they were all in spec. So after a calibration all working well and stable so I'm very happy.
HighVoltage thanks for the tip on moving through the calibration sequence :-+
 

Offline free_electron

  • Super Contributor
  • ***
  • Posts: 8515
  • Country: us
    • SiliconValleyGarage
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #46 on: May 21, 2018, 10:06:16 pm »
Yup. those blue stinkers short out sometimes.
same for the craptalium capacitors. i knock those out by default.
Professional Electron Wrangler.
Any comments, or points of view expressed, are my own and not endorsed , induced or compensated by my employer(s).
 

Offline abnormalalien

  • Contributor
  • Posts: 12
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #47 on: May 24, 2018, 05:33:24 pm »
Hi all,

I'm also working on a faulty 34401a and was wondering if you could explain some of the stuff you've mentioned earlier in this post?

I (guess incorrectly) posted my own thread explaining the particulars of my machine's situation (https://www.eevblog.com/forum/repair/hp-34401a-repair-fails-st-606-609-610-612-613-615-617-618-help/) but long story short, there's something wrong in the Ohm's Current Source part and prob elsewhere too. On here, I've seen several people print out Dr. Frank's schematic and write in their own measurements but I'm a bit confused. I've been assuming the boxed values are what we want; was this run through a circuit analysis software or did you all figure that out by hand (shudders)? Mild curiosity aside...I'm quite unfamiliar with electronics, especially at this level. Can someone let me know exactly what voltage drop I'm supposed to be measuring?

For example, on the far left of the diagram, there's a +7REF line, which you have measured to be 7.012 or 6.994V. You plugged high on a working meter into pin 3 of U201-A? Or somewhere else? Lo is then ground via pin 4 on U201-A? Or lo is the white power line ground from the power schematic? (Does it matter?) What about for the boxed value 12.750: how is that done?

Any advice is much appreciated! Thanks.
 

Online ZuccaTopic starter

  • Supporter
  • ****
  • Posts: 4298
  • Country: it
  • EE meid in Itali
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #48 on: May 25, 2018, 08:25:20 am »
I've been assuming the boxed values are what we want; was this run through a circuit analysis software or did you all figure that out by hand (shudders)?

The boxed values were from my bad unrepaired unit, the one written by hands were from the good Dr. Frank's unit. All of them were measured values from real life.

Beside that, it looks like you have problems to understand a schematics, where the pins are and where to put your DMM probes. I could give you more advises but I am worried you will understad them in a wrong way so please post pictures of what you are measuring, how you do it and where you put the DMM probes.

Worst case we will tell you: You are wrong.

As long you keep your DMM in V reading mode you and the circuits are safe. So you could even do some tests by yourself and with your active brain you will be surely understand some electronics black magic secrects.

There is main voltage in the 34401a, please be very very careful to stay away from that corner.

PS: Do you have hot air (de)soldering equipment? Probably you need to replace some SMD components and without it you will be stuck.
« Last Edit: May 25, 2018, 08:30:08 am by zucca »
Can't know what you don't love. St. Augustine
Can't love what you don't know. Zucca
 

Offline abnormalalien

  • Contributor
  • Posts: 12
  • Country: us
Re: [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621
« Reply #49 on: May 25, 2018, 02:48:29 pm »
Ah ok that makes sense, I apparently missed that. Written values = functional, got it.

I appreciate the concern; while I'm a bit  :-// on the electronics background, I have no intention of dying for my thesis! I once tried to design/implement an electron beam evaporator which involves a high voltage (1500-3000V) but low current circuit using thoriated tungsten wire. This combined two of my biggest discomforts in the field: electronics and radiation...I wound up burning some hair off my arm at 3000V. Yea, that's when that project stopped being a priority.

I understand some basics; I can identify most of the circuit symbols including ground. I think ground is just something that's never really clicked in my brain. Talked to the advisor about it last night; I've been informed there's two, analog and digital, but that in general when I'm troubleshooting, I can probably just use the green line directly connected to the case. Somewhere that ground is connected to power ground (white line in power).

I've attached a couple pictures. In the first you can see I've got a (working) Keysight and a Fluke meter. I'm mostly using the Fluke but occasionally checking results with Keysight. In this one you can also see my lo on the fluke connected via an alligator clip to case ground. I've got a red probe for the positive terminal and have been using that to check voltages. In the other picture, I've circled the U201. As I've understood from this and other sources, that's a common failure. To measure the U201, I would just use my positive probe to check each pin directly?

Ah I'm not sure about the hot air soldering gun. I've got both large and micro soldering stations and I can probably borrow one from another lab in the department. (Most everyone is DIY here, someone's got to have one.) Or I might have one stored in my Dad's old tools. Can check this weekend.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf