Years ago, I repaired welding power supplies. In an early invertor type supply the manufacturer implemented 'auto linking', i.e. using relays to connect correct primary coils depending on 240/240 mains supply. It seemed to work quite well. Then we had a customer with a rack of them powered by a large commercial generator which output 480V (they were installing/building a very large stainless-steel tank that was too large to ship intact). The generator stumbled causing a brown out, the power supplies 'relinked' from 480V to 240V and when the generator started outputting 480V again the whole rack of welding supplies blew up. The manufacturer said, "We did not think of that!". They then changed the control circuitry so that it could not relink automatically from 480V to 240V. When these sorts of convenience circuits go wrong stuff blows up.
@@jheissjr Miller XMT-304 as I recall. Nice design in general. Fan duct (heat sink) down middle so dirt was isolated from electronics. The two power boards were self-adjusting. The 'auto-linking' was originally a problem though.
Agreed - that is excess complexity for such a simple function. A voltage selector switch is way more robust and less expensive. It's not like users would switch input voltage on a daily basis.
Nice one Ian well done, I reckon the problem was that dodgy joint on the relay, we will see what happens when you increase the a/c but then we still have the problems with the 4000 section!. Bob
Great repair so far, Ian. Just to be sure, I run analog boards through an ultrasonic cleaner - 30 minutes in 99% IPA at 50 C. I am currently finishing up repair/restore of two Guildline 9577 7.5 digit bench meters (Solartron/Schlumberger 7075 in disguise). The IC looks like someone used a desolder gun with the tip temperature set way too 🔥!
I'd love to have put the analog board through an ultrasonic cleaner, subject to removing a couple of parts like the LM399, but my cleaner isn't quite big enough. I could maybe do it in two steps, submerging half the board per go. Hmmmm.
@@IanScottJohnston When I decided to get an ultrasonic cleaner I was in the middle of the repair of a Tektronix 544A oscilloscope - of the leaky surface mount capacitor vintage - and wanted to clean the acquisition board after removing the caps. I bought a 22 liter cleaner that will take a 50 cm by 30 cm board in about 12 cm of liquid. Probably overkill but I have yet to come across a board that won't fit 😊
At 13:37 one of the tracks looks a bit the worse for the desoldering experience! My favourite method of removing IC's from thru-plated holes is to cut the legs off then use tweezers to pull out the pins once the soldering iron has melted the solder all through the hole. Desolder braid to suck up residual solder and IPA on a cotton bud to clean up, leaves a nice tidy job. Although, not such a good method if you want to reuse the IC!! I'm still waiting for Santa to bring me one of those fancy desoldering guns.
Those fancy desoldering guns are dirt cheap, admittedly I got mine second hand for £30. It worked admirably on a K2001 front/back switch that was renown to be hell on earth to replace. I just used leaded solder on the pins and sucked it all up. Incidentally, since Tek took over Keithley who did have spare parts I was told NO! NO SPARE PARTS! NO RIGHT TO REPAIR! they even led me up the garden path to a repair and then I would have to send it to Tek in Germany with all the VAT and import costs, etc. Replacing the switch would cost me over £10,000. I have actual joke pro-forma invoices for this. I eventually worked out the proper switch that they will use on a repair is the one they use on all modern Tek/Keithley meters and it is C&K F8UEETB, an 8 pole DT with environmental protection. ETA: I just checked Farnell and the switch is £7.95
Great job so far Ian. Can't be too careful where these types of circuits are concerned. Personally I would opt for a manual override on the mains voltage selection. I wouldn't trust an old Op Amp to make the decision for me. Old motto, if it's auto maybe you augh-to not. 🙂
Good start. I would advise lifting all the replaced caps and checking for any damage under them that might have been missed when they were replaced, never assume the person before you found everything.
@@IanScottJohnston Well, same here. Bit of an eyesore. The soldering during that repair attempt earlier might/possibly has made things turn for the worse :(
For the likes of this Keithly design with more than zero chance of it overvolting, is it worth installing TVS's on the supply rails to protect the expensive electronics?
It is mind boggling the power supply circuit but this meter was for US military use in all theatres of war. It also does 400Hz for aircraft and nuclear submarines. Why a total grunt needs the precision of a 7.5 digit meter but is so idiotic they can't just flip a switch on the power input is beyond me.
I did that on the last K2001 repair, deleted a load of parts and fixed it at 240VAC......but decided to give this one a go. If my confidence remains high that it's be ok......then I'll leave it. Any 'doubt' and I'll rips the parts off.
Wow imagine being that over confident Keithley designer that came up with the 110/220 auto switching for such an expensive equipment. Unnecessary complexity.
For removing the tantalum caps would the smd tweezers that Dave Jones has just reviewed help? Got mine on order 😀 th-cam.com/video/61xuDDVCPx8/w-d-xo.htmlsi=-iO4p6tL4aPVrD7L
Get a 2001M - forget xdevs shit experience with 1990's leaky caps models. There was a massive flood of 2001M (these are all 2005+ when the capacitor shit became irrelavent) when the US Navy flooded the market with K2001's.
Years ago, I repaired welding power supplies. In an early invertor type supply the manufacturer implemented 'auto linking', i.e. using relays to connect correct primary coils depending on 240/240 mains supply. It seemed to work quite well. Then we had a customer with a rack of them powered by a large commercial generator which output 480V (they were installing/building a very large stainless-steel tank that was too large to ship intact). The generator stumbled causing a brown out, the power supplies 'relinked' from 480V to 240V and when the generator started outputting 480V again the whole rack of welding supplies blew up. The manufacturer said, "We did not think of that!". They then changed the control circuitry so that it could not relink automatically from 480V to 240V. When these sorts of convenience circuits go wrong stuff blows up.
I always used to say to the younger guys in our electronics "always consider the 'what ifs'....."
What was the model of the welder?
@@jheissjr Miller XMT-304 as I recall. Nice design in general. Fan duct (heat sink) down middle so dirt was isolated from electronics. The two power boards were self-adjusting. The 'auto-linking' was originally a problem though.
Brilliant Ian =D Wow, that automatic tap selection is crazy... What were they thinking!!! Relays stick / fail to switch over - boom!
Exactly!
Agreed - that is excess complexity for such a simple function. A voltage selector switch is way more robust and less expensive. It's not like users would switch input voltage on a daily basis.
its neat but yes its all on that relay to function and not stick.... scary.
Watching intensely as I have one these DMM's... all is good so far! As usual nice video.
Yay, 2001 saga again? :)
11:29 You should buy the SMD desoldering tweezer iron that EEVBlog recently reviewed. Would make desoldering those tantalum caps really easy.
They are on their way :)
nice one Ian...
Nice one Ian well done, I reckon the problem was that dodgy joint on the relay, we will see what happens when you increase the a/c but then we still have the problems with the 4000 section!. Bob
Danke für das Video.
29:43 Wo bekomme ich diesen (blauen) Trimmer-Schraubendreher. Finde bei AliExpress und Amazon nicht? LG
Farnell 1699878
It's a Bourns H-91 ADJUSTMENT TOOL, TRIMMING POT, 127MM L, BLUE.
@@IanScottJohnston Vielen, vielen Dank! LG
Love these repair videos. I'm hoping for, (but at the same time I'm fairly sure of) a good outcome ;)
Great repair so far, Ian. Just to be sure, I run analog boards through an ultrasonic cleaner - 30 minutes in 99% IPA at 50 C. I am currently finishing up repair/restore of two Guildline 9577 7.5 digit bench meters (Solartron/Schlumberger 7075 in disguise). The IC looks like someone used a desolder gun with the tip temperature set way too 🔥!
I'd love to have put the analog board through an ultrasonic cleaner, subject to removing a couple of parts like the LM399, but my cleaner isn't quite big enough. I could maybe do it in two steps, submerging half the board per go. Hmmmm.
@@IanScottJohnston When I decided to get an ultrasonic cleaner I was in the middle of the repair of a Tektronix 544A oscilloscope - of the leaky surface mount capacitor vintage - and wanted to clean the acquisition board after removing the caps. I bought a 22 liter cleaner that will take a 50 cm by 30 cm board in about 12 cm of liquid. Probably overkill but I have yet to come across a board that won't fit 😊
Nice size.....I'll look at that.
Very nice
At 13:37 one of the tracks looks a bit the worse for the desoldering experience!
My favourite method of removing IC's from thru-plated holes is to cut the legs off then use tweezers to pull out the pins once the soldering iron has melted the solder all through the hole. Desolder braid to suck up residual solder and IPA on a cotton bud to clean up, leaves a nice tidy job. Although, not such a good method if you want to reuse the IC!!
I'm still waiting for Santa to bring me one of those fancy desoldering guns.
Yes, there's a few on that IC that need tweaked......along with a few others dotted around.
Those fancy desoldering guns are dirt cheap, admittedly I got mine second hand for £30. It worked admirably on a K2001 front/back switch that was renown to be hell on earth to replace. I just used leaded solder on the pins and sucked it all up.
Incidentally, since Tek took over Keithley who did have spare parts I was told NO! NO SPARE PARTS! NO RIGHT TO REPAIR! they even led me up the garden path to a repair and then I would have to send it to Tek in Germany with all the VAT and import costs, etc. Replacing the switch would cost me over £10,000. I have actual joke pro-forma invoices for this.
I eventually worked out the proper switch that they will use on a repair is the one they use on all modern Tek/Keithley meters and it is C&K F8UEETB, an 8 pole DT with environmental protection.
ETA: I just checked Farnell and the switch is £7.95
Might have to look out for one of these, I've got 5 1/2 and 6 1/2 digit HP DMM's. slowly working up the number of digits. 🙂
Be careful, it’s addictive. You may need to attend a group or two!
Great job so far Ian. Can't be too careful where these types of circuits are concerned. Personally I would opt for a manual override on the mains voltage selection. I wouldn't trust an old Op Amp to make the decision for me. Old motto, if it's auto maybe you augh-to not. 🙂
My other K2001 I already bypassed the auto-selection so thought I'd go for stock on this one......at the moment anyway!
I want to have a go at repairing one of those, I fixed a 2000 that someone had tried to fix before but botched the initial analogue circuit.
Good start. I would advise lifting all the replaced caps and checking for any damage under them that might have been missed when they were replaced, never assume the person before you found everything.
Thats the plan......they are not sitting right down on the Pcb as it is, which kicks my OCD!
@@IanScottJohnston Well, same here. Bit of an eyesore. The soldering during that repair attempt earlier might/possibly has made things turn for the worse :(
For the likes of this Keithly design with more than zero chance of it overvolting, is it worth installing TVS's on the supply rails to protect the expensive electronics?
Good idea!
Is that an LM399 I see as the voltage ref? The 2001 uses a selected one?
It is a 399, I don’t know about a selected one though.
Maybe it is best if you delete the silly auto-selection circuit and make it fixed for 230V.
That thing is an accident waiting to happen.
It is mind boggling the power supply circuit but this meter was for US military use in all theatres of war. It also does 400Hz for aircraft and nuclear submarines. Why a total grunt needs the precision of a 7.5 digit meter but is so idiotic they can't just flip a switch on the power input is beyond me.
I did that on the last K2001 repair, deleted a load of parts and fixed it at 240VAC......but decided to give this one a go. If my confidence remains high that it's be ok......then I'll leave it. Any 'doubt' and I'll rips the parts off.
I wonder if Keithley has gone to an ARM CPU on the newer versions of the 2001 and 2002?
canny beat an auld Keithley...
Wow imagine being that over confident Keithley designer that came up with the 110/220 auto switching for such an expensive equipment. Unnecessary complexity.
For removing the tantalum caps would the smd tweezers that Dave Jones has just reviewed help? Got mine on order 😀 th-cam.com/video/61xuDDVCPx8/w-d-xo.htmlsi=-iO4p6tL4aPVrD7L
I have them on order! I do have smd tweezers, but they are ancient humongous things!
maybe 1st
SQUEAK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
@@andymouse Cheesey peasey !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
@@fredflintstone1 :)
Based on the large pile of parts, this doesn't seem like a very reliable meter. And based on the prices on eBay (~$1200) I won't be getting one.
Sometimes they are cheap. I bought a 2001m from eBay for 350 USD.
Get a 2001M - forget xdevs shit experience with 1990's leaky caps models. There was a massive flood of 2001M (these are all 2005+ when the capacitor shit became irrelavent) when the US Navy flooded the market with K2001's.
$350 is still not cheap. You can buy a scope for that.
@@simontay4851 This! You can also get a 3.5 digit multimeter for free from Harbor Freight. Who needs a shitty scope?
First! 😄