Keithley 2001 butchery and cosmetic repair help

[Finnaaah]

Hi everyone
I recently picked up a Keithley 2001 for a shockingly good price from someone who imported it from a used equipment seller in China. That is to say, without any way of getting background info. The unit came with fresh calibration from the seller but started throwing up errors and misbehaving, which is when it got passed on to me. It does actually work here and there, and when it does it seems to agree with my other meters on all measurements, but it's very hit or miss getting it there I'm enjoying the process of fixing it, and have included a link to some pictures of the condition it landed in (I think it's an ex e-waste unit)

https://imgur.com/a/RpYCIZQ

I wanted to ask others for ideas on fixing the front panel up. I'm going to restore it's color following TiN's awesome article in which he used hydrogen peroxide and sun. It's pretty yellowed so I'll be using a culturing cabinet at my work to give it direct UV as evenly as possible. The other issue with the front panel is the buttons. The left half work perfectly, but the right half require a fair bit of force in order to register which is a pain when navigating through the menu. Would anyone happen to have a spare membrane sheet of the buttons they're willing to sell (or even better, a front panel)? I've found one seller online but they're asking $330 + shipping for just buttons Otherwise, does building up the carbon patch on the buttons sound like a somewhat sane idea?. The last (slightly mundane) issue related to the front panel was the silkscreen for the power button. Would anyone have experience with touching up faded silkscreen on plastic?

Thanks for any suggestions, and sorry these questions aren't super electronics related

[Laval]

Congratulation on the meter, it's a great unit.

On the 4th picture from the top, there is quite a bit of flux residue. This should be cleaned. If there are other messy spots like that, they should be cleaned as well. Of course, look closely for bad solder joints and bad contact with connectors. A usual problem with these units is the electrolytic capacitors. They tend to leak and cause all sort of issues with other components and the boards. Some people say they had a bad batch of capacitor at the time even from reputable manufacturer. A complete recap is probably in order then see if the problem is still present.

As for the front panel, something that worked very well for my 2001 and my 2015 is bleach. This video shows a method that worked for me at least.



12% (40 vol) peroxide cream works well because it sticks to the surface. You can then wrap it in saran wrap and let it outside exposed to the sun for a few days. It will not become completely white, this is not its original color, but the yellowing should mostly disappear.

https://xdevs.com/ is a remarkable site that contains a wealth of knowledge and data on these devices, I suggest you take a look if you have not already done so.

Be cautious when working on these boards, make sure you use an ESD wrist strap and don't touch the components too much if you don't have to.

[Zucca]

First thing to do is to replace all the electrolytic caps... and check if they leaked already or not.
Do not assume if they look good there is no problem...

Also two caps (should be mentioned in the xdev) need higher voltage rating....

[Overspeed]

First thing to do is to replace all the electrolytic caps... and check if they leaked already or not.
Do not assume if they look good there is no problem...

Also two caps (should be mentioned in the xdev) need higher voltage rating....

Hello

the link for the 2000 cap problem

Question : Also two caps (should be mentioned in the xdev) need higher voltage rating....
can you put more information / link thanks

https://www.eevblog.com/forum/testgear/keithley-2000-and-the-leaking-caps

Regards
OS

[Finnaaah]

Congratulation on the meter, it's a great unit.

On the 4th picture from the top, there is quite a bit of flux residue. This should be cleaned. If there are other messy spots like that, they should be cleaned as well. Of course, look closely for bad solder joints and bad contact with connectors. A usual problem with these units is the electrolytic capacitors. They tend to leak and cause all sort of issues with other components and the boards. Some people say they had a bad batch of capacitor at the time even from reputable manufacturer. A complete recap is probably in order then see if the problem is still present.

As for the front panel, something that worked very well for my 2001 and my 2015 is bleach. This video shows a method that worked for me at least.



12% (40 vol) peroxide cream works well because it sticks to the surface. You can then wrap it in saran wrap and let it outside exposed to the sun for a few days. It will not become completely white, this is not its original color, but the yellowing should mostly disappear.

https://xdevs.com/ is a remarkable site that contains a wealth of knowledge and data on these devices, I suggest you take a look if you have not already done so.

Be cautious when working on these boards, make sure you use an ESD wrist strap and don't touch the components too much if you don't have to.

I have no idea how the last owner managed to get so much flux under there, I've just desoldered it and cleaned that up (bye bye calibration) along with all the other flux I could find. I believe that could be what caused some of the errors which could be explained by small leakage currents, there was lots of flux and grime on the A/D board. Looks like whatever solder was used was pretty terrible quality, the flux has eaten off some of the solder mask and the smell was unbearable Thanks for the video on the whitening process, there's some useful info in there. I'll order some of the cream and maybe try find a liquid oxi booster, the result in that video looks pretty amazing In TiN's/xDevs article, he mentioned some of the text on the screen was damaged in the process. Did you tape up the screen, or find that it wasn't an issue? I'm worried that the text will just peel off considering it's age

First thing to do is to replace all the electrolytic caps... and check if they leaked already or not.
Do not assume if they look good there is no problem...

Also two caps (should be mentioned in the xdev) need higher voltage rating....

Fresh caps just arrived, I desoldered all the original caps first thing and luckily no leaking at all. I was surprised considering their date-codes and the absolute havoc I've seen them wreak on others boards

Will post some photos of the retrobrighting after it's finished 

[Laval]

You can tape the screen and be careful not to spread too much cream on it. You can also remove the screen, it is glued with two sided tape and can be removed with a large and thin plastic spudger. But just put some painter tape that doesn't leave residue.

Again, don't expect it to become white but the yellowing will go. The video is a bit misleading, lighting makes it look more white then it really is.

It might not be a bad idea to repair the scratched solder mask with a pen (pen that apply solder mask).

[Zucca]

First thing to do is to replace all the electrolytic caps... and check if they leaked already or not.
Do not assume if they look good there is no problem...

Also two caps (should be mentioned in the xdev) need higher voltage rating....

Hello

the link for the 2000 cap problem

Question : Also two caps (should be mentioned in the xdev) need higher voltage rating....
can you put more information / link thanks

https://www.eevblog.com/forum/testgear/keithley-2000-and-the-leaking-caps

Regards
OS

OS,

this should be the information needed, still need to double check it.



Just double check the schematics and the stock cap voltage rating... it is very easy to spot.

I have repaired and will sell soon my K2001 (upgraded to DMM7510), so I will go in details soon I do not have the time now.

Arguably the biggest design mistake made by Keithley Developers. I think they just accept the risk or going with a lower cap voltage rating for some reason, they can't have missed it.

[macboy]

I have done "retrobrite" on 9 or 10 Keithley front panels, with great success. I had one bad experience early on, when I left the panel in the peroxide too long (about 1 day) and it bleached out quite a bit. The silkscreened lettering also softened and was damaged a little when I washed the panel afterwards.
Here is my recipe for success:
1. Scrub the panel very well in warm water and dish soap (washing up liquid).
2. Dry well; I used compressed air to blast away the water.
3. Wash well with a lot of 99% IPA isopropyl alcohol.
4. Dry again. Don't touch with oily finger tips. Use gloves.
The above prepares the surface and is important. It first removes oils which might block the water based peroxide from getting in, then the IPA deeply dries out the outermost later of the plastic so that it will absorb the peroxide better. That's my theory anyway.
5. Using "40 vol" peroxide, paint the stuff on, it should have a thick creamy consistency.
6. Place face up in large shallow container and cover the container completely with plastic food wrap (I use "Glad wrap" brand). You can put a little water in the container to keep the humidity level high which helps prevent the peroxide from drying out.
6. Place in mid day summer sun. Rotate container every 5 or 10 minutes for even exposure. Check peroxide for drying out and apply more if needed.

I get complete removal of mild to moderate yellowing with no bleaching of the grey color within only 20 to 60 minutes. No joke.  If you leave it for a long time, the color will begin to bleach out. Maybe the fast speed can be attributed to the prep stage.  Extreme yellowing might never be completely removed.

[Finnaaah]

I have done "retrobrite" on 9 or 10 Keithley front panels, with great success. I had one bad experience early on, when I left the panel in the peroxide too long (about 1 day) and it bleached out quite a bit. The silkscreened lettering also softened and was damaged a little when I washed the panel afterwards.
Here is my recipe for success:
1. Scrub the panel very well in warm water and dish soap (washing up liquid).
2. Dry well; I used compressed air to blast away the water.
3. Wash well with a lot of 99% IPA isopropyl alcohol.
4. Dry again. Don't touch with oily finger tips. Use gloves.
The above prepares the surface and is important. It first removes oils which might block the water based peroxide from getting in, then the IPA deeply dries out the outermost later of the plastic so that it will absorb the peroxide better. That's my theory anyway.
5. Using "40 vol" peroxide, paint the stuff on, it should have a thick creamy consistency.
6. Place face up in large shallow container and cover the container completely with plastic food wrap (I use "Glad wrap" brand). You can put a little water in the container to keep the humidity level high which helps prevent the peroxide from drying out.
6. Place in mid day summer sun. Rotate container every 5 or 10 minutes for even exposure. Check peroxide for drying out and apply more if needed.

I get complete removal of mild to moderate yellowing with no bleaching of the grey color within only 20 to 60 minutes. No joke.  If you leave it for a long time, the color will begin to bleach out. Maybe the fast speed can be attributed to the prep stage.  Extreme yellowing might never be completely removed.

This worked great. I wasn't hoping for it to completely revert, just remove the deep yellow tint. I left it for maybe 3 hours in the afternoon sun, it came out well aside from some patchiness around the text (I went lighter there because I didn't want to damage the printing). The printing seemed to get damaged when I was cleaning anyway, might be my fault for cleaning too aggressively.

Overall really happy with the results, the difference is night and day 

Some negligence on my part screwed me. I installed one of the new electrolytic caps backward, made me jump when  it popped  Thought I was lucky getting out of this without having to touch any electrolyte 

[Laval]

Some negligence on my part screwed me. I installed one of the new electrolytic caps backward, made me jump when  it popped  Thought I was lucky getting out of this without having to touch any electrolyte 

On all Keithley equipment of that era I have worked on (2001 and 2015) the polarity of the electrolytic capacitors is always indicated on the board. There are indeed two indications: most of the time, a + sign is written on the silk screen and if it is not, the pads have specific shape. The square pad is the positive and the round pad is the for negative lead.

[CM]

I replaced the caps in my Keithley 2001, as they are probably decade old caps.  I stuck with what were originally in the unit, the Nichicon high temp 105 degree UVZ caps.  I guess Keithley chose those for thermal stability.  I did increase the voltage rating for caps C116 and C117 fromt 35V to 50V (the same as C108), as the bootstrap voltage can be as high as 39V, and from what I've seen, leaking with severe damage occurs around those caps.  I also increased the voltage rating on the caps to the digital board (C624, C630 and C633), as I observed a little leaking around C624.  Also, I had some broken Molex connectors.  If you need to replace the analog board connectors, the part numbers are 26-60-4030 (for the three pin connector) and 26-60-4050 (for the 5 pin).  You have to remove the center pin of the new 3 pin connector.