No.090 - Keithley 2001 7.5 digit Multimeter Repair - Part 4

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This is Part 4 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 out how the pre-regulator & line voltage selection works on the analogue board then start troubleshooting.
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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12 июл 2024

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Комментарии : 65

@IanScottJohnston 2 года назад

The more I think about the auto 110/220Vac and Hi/Lo selection the more I think I'll bypass it, and maybe come up with a bit of kit to allow others to retrofit on their K2001. Hmmmmm!

@jonka1 2 года назад

How designers bright enough to create an instrument like this thought that mains selection circuit was a good idea is beyond me. Surely a design that defaults to a safe condition is not asking for too much.

@johnshaw359 2 года назад

@@jonka1 "It's safe" if you are in the US. They should have fitted a secondary side OVP if they wanted to be elaborate.

@IanScottJohnston 2 года назад

The donor boards came from a non-240Vac country, so I think i'll take a look at it and work out whats blown coz maybe, in hindsight, I should be looking at this board to fix especially if i will be by-passing the pre-regulator circuit etc. Hmmmmm!

@johnshaw359 2 года назад

@@IanScottJohnston I wonder if any of the rectification components are damaged from Over Volt.

@unmountablebootvolume 2 года назад

@@IanScottJohnston When considering the fact that every single chip on the original board is trash, it might be better to repair the parts board, especially since the parts from the parts board could still be broken, so even if you move everything over to the original board, you still have to deal with any problems the parts board had before plus any possible mistakes that could have happened while moving parts over and maybe even parts that broke from the heat of de- and resoldering them. I would just bypass the corroded autoswitch and fix the parts board instead, as that one at least seems to not be completely fried, so there is at least any chance of fixing it.

@brianmiller6320 2 года назад

You know that you want to fix it rather than fit the donor board, this is better than Peaky Blinders! Good luck.

@DrFrank-xj9bc 2 года назад

I already shuddered when I followed Illyas / TiNs repair reports on these Keithley DMMs. They were really badly designed, also lacking circuit FMEA, obviously. This automatic 110/240 V switching is over engineered and dangerous. No robust design at all. But that really might be a lot of fun to further dig into this PCB. Great analysis, and entertaining videos, as always!

@IanScottJohnston 2 года назад

I agree.....and when I get to it I'll only use the auto switching if I am confident in it working.......given my line voltage is close to 245VAC here in the UK!.....else it will get bypassed.

@DavidSmith-zx7wz 2 года назад

Absolutely love the repair videos!! Thanks

@hempbear 2 года назад

Boy, oh boy, you're really going down the mother of all rabbit holes here. You're a brave man. :D It really is likely every single IC is blown, including those on the A/D board :(

@IanScottJohnston 2 года назад

Hence the rabbit hole animation around the 16min mark......:)

@TheDefpom 2 года назад

Keithley certainly over complicated the ACvoltage switching there, I’m sure a manual switch would have been far better!

@IanScottJohnston 2 года назад

If they weren't stupid, then its possibly in order to keep the temps and current down to a minimum being a 7.5digit DMM.

@GadgetUK164 2 года назад

=O This multimeter has been a nightmare! Always excited for the next episode!

@allthegearnoidea6752 2 года назад

Great video I always learn so much watching you work thanks Best regards Chris

@JLCPCB 2 года назад

Very interesting video! 😁

@reallyniceaudio 2 года назад

amazing video!

@piconano 2 года назад

I see a video from you, I drop everything. They can wait.

@bfx8185 2 года назад

Keep going on weekly bases ;) Thx and good luck!

@jrworpjrworp7254 2 года назад

Never ending repair

@motionsoftwaresim 2 года назад

Enjoying your videos; I've been down similar rabbit holes with other Keithley meters. On my working 2001. U107 15k and 83 Ohm, U102. 40k and 500Ohm, U108 12k and 600Ohm. Look forward to your next episode.

@IanScottJohnston 2 года назад

Thanks for that.....something to aim for. Cheers!

@sdgelectronics 2 года назад

The bridge rectifier arrangement is the same in the video I did a while back on a V-Pro AC dimmer, to allow a MOSFET or IGBT to switch AC.

@IanScottJohnston 2 года назад

@chrisstott8580 2 года назад

It goes back a very long time. I came across this idea on the paper tape punch of an Elliot 503 computer where a scr was used to switch the power to the motor. No opto-coupler, pulse transformer driven by an unijunction oscillator... Made sense at the time.

@IanScottJohnston 2 года назад

Just had a look at your video, and yep it's the same idea. For a dimmer fine, but a 7.5digit DMM ugghhhh!

@qzorn4440 2 года назад

this is a simply wonderful trouble-shooting video 🥰 speaking of shooting do not let the russians see this 2001 7.5 digit info... or they will copy it and make one with vacuum tubes 🤔

@fredflintstone1 2 года назад

Yea part 4 quickly following part 3 🙂

@davesherman74 6 месяцев назад

Interesting, for as long as I worked at Keithley I did not realize the 2001 had that auto line voltage detection. I suspect the 2002 does as well, it was closely related to the 2001. Everything else was manually selected or used off-the-shelf switchers that could handle 100-240 volts automatically. FYI, the GPIB address lost pointed to the bad EEPROM. It would save the default so now that you've got a good EEPROM you shouldn't see that one anymore. The calibration data does not get saved until the calibration is completed.

@IanScottJohnston 6 месяцев назад

Yep, it’s a shame and talked about quite a bit that we can’t save individual functions individually like VDC. Have to run through the lot first.

@gjvdspam 2 года назад

Like the -/+ 15V rail component search. Nice idea / format youtube channel. Not another Dave copy channel

@FireballXL55 2 года назад

Hi Ian, I would be tempted to use your dual rail bench PSU and current limit the output and wind it up and check for hot spots with you IR camera.

@IanScottJohnston 2 года назад

Thats coming, i like to get the obvious off the table first. Mind you, things are taking a slightly different turn.....wait for Part 5....:)

@mr1enrollment 2 года назад

Ian, in a word PUNT. I know I would hate to give up, but the history and your observation regarding the line switching -(I suspect you are correct), leads me to believe even if you get it running - it will fail soon after. I would use your 'donor' board as the one to fix. Toss that dog in the trash, it is not worth the effort and risk of future failure. ;-} cheers

@IanScottJohnston 2 года назад

I don't need a 7.5 digit K2001, I got this faulty unit to have some fun trying to repair it (my fav hobby!) and to make some cool content for my YT channel. If the analogue board (and the digital board for that matter) were the newer versions then I might have turned to fixing up the donor boards, but they are not.

@douro20 2 года назад

There were some digital film recorders which used GP-IB. One of them was the Matrix PCR which could produce 4K images with 16.7 million colours- and this was back in 1984.

@DextersTechLab 2 года назад

Interesting you mention Matrix, a friend of mine has just picked up a Matrix film recorder (sans the camera) which he used to use in the 80s to generate slides from a Quantel Paintbox. If anyone has any camera bodies from a Matrix recorder we would love to find them.

@simontay4851 2 года назад

wow, 4K in 84. Thats amazing. Bet it was bloody expensive.

@douro20 2 года назад

@@simontay4851 Actually a bit better than 4K. It had a resolution of 4096x4096.

@IanScottJohnston 2 года назад

@@douro20 4096x4096, is that the formula for working out the cost back then......:)

@Drew-Dastardly 2 года назад

That AC input switching is crazy! What's wrong with the usual slide switch/fuse holder on the back? Does the 2002 also have this over complicated scheme?

@IanScottJohnston 2 года назад

As far as I know yes, the schematics are shared between the two models.

@DextersTechLab 2 года назад

wow, i can't understand how they could have thought switching for 220/110 like that was in any way safe

@donreid358 2 года назад

When testing the negative regulators it looked like you had the polarity of your probes reversed. Don't you need the negative side on the output of the regulator?

@IanScottJohnston 2 года назад

The resistance readings are the same either polarity. There are soooooo many devices/parts connected on those supply lines it makes little difference.

@irgski 2 года назад

Can you use your thermal camera along with using an external current limited psu to look for “hotspots”? BTW - what thermal camera do you use? I’m going to venture an opinion here…I think that you now have TWO donor boards!!!

@IanScottJohnston 2 года назад

I use a Flir C2 which I have modified so it's optimum at about 6" from the Pcb.......stock C2 needs 12" or more.

@simontay4851 2 года назад

I bet every single IC on that board is fried. This ain't going to be a cheap or quick repair and could get frustrating. This is going to be A LOT of work.

@johnshaw359 2 года назад

I'm was looking at the schematic at the 110/220v switch and thinking, mmm, is that auto sensing. I would try to do away with that if It's safe to do so.

@KD0CAC 2 года назад

Need to sell more meters - so engineer cascade failures into a product ? To get 6,7,8 or so digits --- put a bunch of cheap meters in series ? ;)

@DavidSmith-zx7wz 2 года назад

Maybe adding a crowbar circuit to the secondary somehow?

@KD0CAC 2 года назад

Seems like it should have a box full of crowbars ;)

@fredflintstone1 2 года назад

why on earth did they use such a complicated way to switch from 240-110 volt ac input???

@IanScottJohnston 2 года назад

I guess as it's a precision instrument they found it necessary to manage heat and current consumption as much as they could. But, one glitch and it's fried!

@fredflintstone1 2 года назад

@@IanScottJohnston yes but it seems a dangerous way to do it as well as complicated and the adds more danger

@stazeII 2 года назад

Could also be was designed in US, where we have 110/120, and if it failed with only 110v everything would just end up undervolted, no harm done. But yeah. Seems like a weird design…

@mr1enrollment 2 года назад

also: if you do use the donor, then chop out that stupid line 240/120 switch and hard wire for your 240v, not worth the risk again. IMHO it was a terrible choice to design an auto switch. Especially since no one needs an instrument to auto set every time it is turned on,... really dumb idea. Even smart engineers make stupid choices sometimes,.... blush.

@IanScottJohnston 2 года назад

Thats something I am contemplating, but it will depend on the testing and confidence I will have on that switching. Also, the pre-regulator system may be keeping temperatures/current consumption down in the unit......I'm thinking there gotta be a reason they didn't just fit a switch!

@mr1enrollment 2 года назад

@@IanScottJohnston LOL, it is a cute circuit, I am sure the guy was proud. But it is a risky thing to do, my bet is it was more pride than practical. After all, an IEC filter/fuse is simple, well proven, without any nasty silicon that risks the entire unit. Good luck what ever you choose, it makes a good video. dan

@ahmedalshalchi 2 года назад

Bro Ian .... What a stinky muddy swamp did you put yourself in ??... Get out quickly before you probably re-manufacture this K2001 unit again ... Damn , was this truly Keithley design and made ??

@milantrcka121 18 дней назад

That complex yet convenient (and idiot-protection?) line voltage switching system appears to be a potential source of a "single-point failure" which, if faulted, will destroy the rest of the unit. In a medical instrumentation and aerospace systems, unacceptable. Is this what happened here?

@IanScottJohnston 18 дней назад

Yep, common issue with these meters……sadly!

@irgski 2 года назад

What a terrible choice by the original designer! To trade off automatic ac mains selection over - potentially- destroying the whole pca! The mains fuse probably would not react fast enough before major circuit damage.

@jaycee1980 2 года назад

That line selection circuit is just stupid, and completely unneccesary. It's the sort of thing youd set ONCE, maybe twice in the product's lifetime, and leave it there... ie, a switch. Completely overcomplicated design which has of course failed and caused extensive damage as a result. I'd be disconnecting the lot of it and just hard wiring it for the appropriate line voltage