No.087 - Keithley 2001 7.5 digit Multimeter Repair - Part 2

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This is Part 2 of the repair of my Keithley 2001 7.5 digit Multimeter. Picked up quite cheap I was hoping for an in-depth repair.....and it certainly hasn't disappointed so far!
In this video I work on the Digital Board to get it powered up and then the Display to try and get it running.
Part 1:
• No.086 - Keithley 2001...
Part 2:
• No.087 - Keithley 2001...
Part 3:
• No.089 - Keithley 2001...
Part 4:
• No.090 - Keithley 2001...
Part 5:
• No.091 - Keithley 2001...
Part 6:
• No.092 - Keithley 2001...
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Опубликовано:

6 авг 2024

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Комментарии : 58

@allthegearnoidea6752 2 года назад

It’s really a master class watching you fault finding based on excellent knowledge of the circuit operation. I hope you find the firmware after all your hard work.

@xDevscom_EE 2 года назад

Controller chip from K7001 will work fine, they are identical. I wouldn't gradually increase/decrease power supply voltages as those chips not designed for that. E.g. set to 5V supply and power on/off instead.

@Chris_Grossman 2 года назад

I would agree not doing the slow ramp on the 5V supply since the power-on reset time constants are short compared to the slow ramp and the instrument may not power up in the proper state.

@feedback-loop 2 года назад

Yeah, I would agree with this. Just set a reasonable current limit and turn it on.

@Richardincancale 2 года назад

6 ohms is the cold resistance of the VFD filament - remember the resistance will rise as the temperature goes up

@mr1enrollment 2 года назад

Wow, you have patience. This thing is a mess. My bet is that the 5v reg croaked and cooked the whole thing, or maybe the 60v transistors went south, and began the cascade. In either case - it is a mess. I commend your commitment. I do worry that when you get it running, there may yet be some crippled chips that may persist and fail later. A long run on the bench post repair will be a good idea. No doubt you know that. Cheers!

@reallyniceaudio 2 года назад

"I''m dreaming!" love it!

@keithlambell1970 2 года назад

Impressive diagnostic skills and perseverance sir. Looking forward to the next installment :-)

@robbieaussievic 2 года назад

.... I think his address is 221b Baker Street.

@reps 2 года назад

Unfortunately I have don't have a Keithley 2001 any more, but I remember looking at model 7001 system switches as possible front panel / VFD donors. They are often cheap and the VFD + driver board should be identical

@IanScottJohnston 2 года назад

Oh!......Cheers thanks, will see if that opens up a possible solution

@gbowne1 2 года назад

@@IanScottJohnston yeah they are almost identical and form factor too. I didnt think about the VFD being the same.. probably is.

@largepimping 2 года назад

@@IanScottJohnston Can say from experience that they're swappable.

@bansci 2 года назад

I might have one and I'm down the road from you. I'm in Qatar this week but can check next week. Will post again if I do

@bansci 2 года назад

@@IanScottJohnston I have a Keithley 7002 with a good display if you're still looking/

@brainndamage 2 года назад

I'd try turning on the supply at once, not slowly. Maybe one of the chips doesn't like it.

@SpeccyMan 2 года назад

Definitely in depth and clearly there is more to come. Fascinating.

@simontay4851 2 года назад

You should build a crowbar over voltage protection circuit on the output of the 5V reg using a fuse, a 5.1V zener and an SCR. If the 5V reg ever fails again in the future, the zener will conduct, SCR will turn on and short the supply. Maybe also use a switching regulator for better efficiency.

@sdgelectronics 2 года назад

It might be a good design philosophy for any project with expensive components on it!

@donepearce 6 дней назад

I'd think about leaving a scope on the power rails, triggering on runt negative edges. Inexplicable behavious in my experience is frequently down to rail glitches.

@andymouse 2 года назад

Good work and tense stuff!...cheers.

@fredflintstone1 2 года назад

Wensleydale Cheese!!!!!!!!!!!!!

@davesherman74 7 месяцев назад

Kind of late to the party, but if the display micro was running, it would default to displaying "No Comm Link" on the VFD. Once the main micro starts talking to it it should be displaying the model number and version. The "No Comm Link" was to indicate the display board was working but the main micro was not.

@daveodessa 2 года назад

You certainly set some challenges for yourself. Lets hope you get a good result.

@peternewman958 2 года назад

I use Brasso to clean and polish bezels of Acrylic.

@mariomionskowski6223 Год назад

You should build a crowbar for the 5V powersupply.

@DavidSmith-zx7wz 2 года назад

Good Stuff! Thanks

@NotMarkKnopfler 2 года назад

Just as an aside, whilst those teflon cables are very handy, have you ever pulled the ends off and looked at how much cable there isn't? There's hardly any steel cable in them - it's a scandal! I have had a situation where the teflon cables/connectors simply couldn't carry the current required. Maybe try some thicker cables for the power supply lines to the VFD? Greets fi Aberdeen!

@SidneyCritic 2 года назад

You can polish Perspex/acrylic clear with automotive polishes, ie, the paint on show cars ends up like glass. Cutting compound is too course so I would use 2nd cut/rejuvenator and finishing polish.

@GadgetUK164 2 года назад

What a nightmare! One thought that crossed my mind - is it possible the CPU is just not booting properly because of the gradually voltage increase as you bring the 5v level up? I would be tempted to perhaps reset the CPU manually if bringing it up that way I think! That said, that logic level isn't right on that serial pin you ended on, so most likely a fault there I guess?

@IanScottJohnston 2 года назад

RESET happens after the voltage reaches 5.0Vdc, so it's no problem (otherwise it would be a problem). Today I am no longer ramping up the supply like I was.....was only till I had more confidence in the circuit despite even having a low CC limit. I am now using my BB3 psu to power it......and it's reacting exactly the same.

@GadgetUK164 2 года назад

@@IanScottJohnston I did wonder that - sorry if you mentioned it and I missed that part! I know some of the Amigas work that way too. At least you know that isn't the issue!

@TheEmbeddedHobbyist 2 года назад

Let hope they have not put the read protection on that display micro, or it could be a bugger to get the data out of it.

@qzorn4440 2 года назад

very neat info... could be some of the other components have been weakened from the 5vdc issue and will show up on a hot day? 🤔 thanks really like these videos. 🥰 it would be sweet if the chip people could make one chip designed for 6.5 or 7.5 digit meters... the demand for high resolution meters is growing... ✌

@fredflintstone1 2 года назад

Hmm cliffhanger ending I hope you find the firmware🙂

@alpcns 2 года назад

What a trainwreck this instrument is! Did they zap it in a cyclotron or something? Terrible. Luckily you enjoy this stuff... I'm gobsmacked by the patience (and knowledge) you possess with these complex circuits. Thanks for sharing again!

@Drew-Dastardly 2 года назад

While the display panel is waiting for parts have you tried using the meter using GPIB or RS232? It is likely set up with factory default enabled, if not just cycle through GPIB addresses looking for it with *IDN? and failing that RS232 with typical 8,N,1.

@IanScottJohnston 2 года назад

Good idea!

@Blowcrafter 2 года назад

I'm kinda concerned that the 60V supply was what nuked the 5V. If the incoming supply was what killed things I'd have expected the filament to blow too.

@IanScottJohnston 2 года назад

Good point.

@mixolydian2010 2 года назад

HI, love the videos and learn so much about troubleshooting from them. I wonder, if you dont mind the question, you use the bm786 and i think you used the 121gw in the recent past. I cant seem to find a comparison of the two. I have the 121gw and bought it around 2 years ago and consider it my best multimeter, out of the 3 i own. Was hoping maybe you explain the differences to me. Take care.

@IanScottJohnston 2 года назад

I have never compared the spec, I just changed to the 786 purely because its a bit faster and the digits on the display are bigger for my YT videos.

@mixolydian2010 2 года назад

@@IanScottJohnston hi Ian,thanks for the reply. I wondered if it took a reading faster or was more accurate. Cheers.

@SoddingaboutSi 2 года назад

The resistance of the filaments will be low when cold anyway. At 5v the current may well drop? Also are these circuits OK soft started?

@IanScottJohnston 2 года назад

Well, the Cpu is anyways as it resets via the supervisor IC only after 5.0Vdc is reached. Just doing it till confidence is reached on the board (mainly the display board) despite using CC mode. I'm now using my BB3 PSU without soft-start and everything is the same.

@twobob 2 года назад

solid, choker how mangled it was/is

@hamandwine 2 года назад

I consider the VFD completely fine. But could it be that the VFD driver chip is bridging the 60V to the 5V by an internal fault? That would explain why a lot of chips may have died from high-voltage impact.

@raymiller5738 2 года назад

Re the display polishing, just use toothpaste ..and elbow grease. At worst a car headlight restoration kit if the damage is really bad. good luck with the display CPU.

@gerhardwiesinger 2 года назад

Which polishing paste did you order?

@IanScottJohnston 2 года назад

From Ebay = QUIXX XERAPOL ACRYLIC PLASTIC POLISH PERSPEX SCRATCH REMOVER RESTORATION KIT QA1

@964tractorboy 2 года назад

@@IanScottJohnston You could also try polyWatch: much beloved by watch collectors. There are two types: one for plastic and another for mineral glass, so be careful when ordering.

@seanbosse 2 года назад

I have a spare 2001 display, but it's labeled 7001-800A01. Not sure if that's any help to you.

@IanScottJohnston 2 года назад

Probably just an older rev which would be fine................can you contact me via RU-vid or my website.

@IanScottJohnston 2 года назад

www.ianjohnston.com

@c4t4l4n4 2 года назад

I remember watching Marco Reps repairing the same multimeter @ ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-HVDQeJTEHFI.html Oops, didn't see the comment below 🤔

@feedback-loop 2 года назад

A dead CPU with firmware does not look promising :(

@IanScottJohnston 2 года назад

A way forward is in progress.......fingers crossed!