Keithley 2001 Repair (Bad Capacitors) - Page 1
Forum section: electronics / repair

author: derZockerMP
author_rank: Regular Contributor
timestamp: June 24, 2024, 06:19:15 am
content: [ Specified attachment is not available ]Hello, I recently purchased a Keithley 2001 in non-working condition.The seller said it wouldn't even turn on. Then I received the device, I tryed to repair. The error was clearly visible. Leaked capacitors...The corrosion on the board was so heavy that several IC footprints came off the board and a short circuit even created a hole in the board.Do you think it is repairable? The digital board works yust fine. [ Specified attachment is not available ]

author: Harry_22
author_rank: Frequent Contributor
timestamp: June 24, 2024, 10:49:07 am
content: This device must be repaired.Wash the board using Flux Off or Contact Сleaner sprays. Unsolder the chips under which electrolyte may have gotten. Check all traces and especially vias.Then you can cover all with Solder Mask Ink.If it doesn't work, write. I have 2000.

author: derZockerMP
author_rank: Regular Contributor
timestamp: June 24, 2024, 01:24:21 pm
content: Today I desoldered all ICs in the contaminated region. There was plenty of electrolyte under there. I also made some X-Rays of the Board. It seems that the inner Layers are not that problematic. I will order some new components today and then start to rewire the lost traces and measure for conductivity according to the schematics. On the 15V Rail to Com I meausure 80Ohm that is little bit to high to my thought. -15V stands around 1,5kOhm. I think there must be an short either.

author: bson
author_rank: Unknown
timestamp: June 24, 2024, 06:31:59 pm
content: Replace the most affected chips too, what looks like two MC14094B latches and one LM358 opamp. These are jellybean parts. The originals might still be fine, but they cost nothing and you don't really know how badly corroded the pins are, so I'd just replace them.

author: jonsikul
author_rank: Contributor
timestamp: October 19, 2024, 12:25:13 pm
content: derZockerMP, do you happen to have any good photos of the PCB in the area of the electrolytic caps? I am specially interested in the area between C116 and C117 since my PCB has basically burnt a hole there and I can't tell how the middle layers route there. Did you finish your repair and solder in new electrolytics?

author: BennoG
author_rank: Frequent Contributor
timestamp: October 19, 2024, 05:18:57 pm
content: have you looked over herehttps://xdevs.com/review/kei2001m/if need more I have a working 2001 and need to open up 1 to replace some components.Benno

author: bastl_r
author_rank: Regular Contributor
timestamp: October 19, 2024, 06:37:36 pm
content: HiCan you tell me the gap between the pins of the electrolytic capacitors.Are there 5mm or 7,5mm?

author: jonsikul
author_rank: Contributor
timestamp: October 19, 2024, 06:52:39 pm
content: Benno,I have, but there seem to be at least 2 versions of the PCB, one with the diodes (CR109 - CR112) on the top side in between the electrolytic capacitors and the other one with the diodes on the bottom side. My PCB (from 1992 I think) has them on the bottom side, whereas almost all the photos I have seen so far have the other version and are therefore not usable for me since it is routed different.RegardsJonsikul

author: jonsikul
author_rank: Contributor
timestamp: October 19, 2024, 06:56:05 pm
content: Bastl_r,I am not sure if this question is for me or not, but the space is 5mm

author: jonsikul
author_rank: Contributor
timestamp: October 19, 2024, 07:05:53 pm
content: In the photo attached you can see how my PCB is messed up. There are for sure multiple things wrong with this 2001 but I would like to know if and how the middle layers are routed around the burnt area to move forward. Best way is to have a light at the PCB on the backside and take a photo of the top side and vice versa.

author: BennoG
author_rank: Frequent Contributor
timestamp: October 19, 2024, 07:26:22 pm
content: sorry mine is from 2011 (repaired for parts from e-bay).But remove all the charred pcb because the carbon in it will conduct current and burn down your PCB, do not leave any trace of carbon on the pcb.I learned the hard way on an TDK lambda the hard way. The pcb has now a hole of 2 x 2 cm (1 x 1 inch) and flying wires to the bridge rectifier. (sorry could not find a photo of the hole)Benno

author: bastl_r
author_rank: Regular Contributor
timestamp: October 19, 2024, 10:30:55 pm
content: Quote from: jonsikul on October 19, 2024, 06:56:05 pmThank you.I has a 2002. The powersupply area is maybe the same and and I would like to replace the capacitors before they leak. But I don't want to remove the mainboard unnecessarily, so I'll just rely on your information.Where can I send the invoice if the information was wrong?Joke...regards

author: derZockerMP
author_rank: Regular Contributor
timestamp: October 20, 2024, 10:40:44 am
content: Hello, your PCB looks like mine: broken. But I didn't repair mine because of a broken transformer. Then I received an even more broken unit with a faulty AD converter. I can provide some X-rays of the PCB if necessary.

author: jonsikul
author_rank: Contributor
timestamp: October 20, 2024, 11:47:33 am
content: An X-ray would be really valuable and appreciated. Attached is a photo of my current board as I believe I have removed all the charred part as Benno mentioned. With my mill I have found 1 trace on a middle layer that I need to find out where it goes. It is thick so I guess it's a power trace. I am afraid there are some very thin that I haven't seen, so an X-ray might help with that.Next step for me would be to try and connect any middle layers and fill with epoxy.How did you find out your transformer was broken? Did you just measure the windings with an ohmmeter or do you see some visual problems?

author: BennoG
author_rank: Frequent Contributor
timestamp: October 20, 2024, 12:44:17 pm
content: what happened to U509 looks like crackedBenno

author: jonsikul
author_rank: Contributor
timestamp: October 20, 2024, 12:52:29 pm
content: Just some flux I guess, it cleans right off.

author: derZockerMP
author_rank: Regular Contributor
timestamp: October 21, 2024, 10:40:47 am
content: Good job with the cleaning.Did you desolder the other ICs that are not directly corroded? Because underneath, in most cases, there is also corrosion that is not a problem yet but could be in the future.Then I rewired all the corroded parts on my board, put it all back together, and started an initial smoke test. Then nothing happened, and all the voltage was lost in the white ceramic resistor used for voltage preselection. So the transformer had too low resistance. First, I searched the voltage selection circuit for a problem because that's often where the problem is. But then I connected the transformer directly to an AC source, and it was drawing too much power without anything connected.I will post X-rays this afternoon.

author: derZockerMP
author_rank: Regular Contributor
timestamp: October 21, 2024, 07:34:47 pm
content: Here attached some X-Rays of the corroded spot. Hope the pictures show everything what you need. The top Layer is maybe not shown because of corrosion on the PCB.

author: jonsikul
author_rank: Contributor
timestamp: October 21, 2024, 08:22:35 pm
content: derZockerMP,That's amazing, thank you so much, you are a life saver! I believe I can see everything I need in the picturesDo you just happen to own an x-ray machine? I am so envious.Best regardsJonsi

author: jonsikul
author_rank: Contributor
timestamp: October 21, 2024, 08:28:23 pm
content: I have only removed U505-U508 along with U513 and cleaned underneath them. I guess you are right, I should probably remove more and make sure it is fully clean for the future. As of now, I am not sure if my transformer is damaged, I have yet to test it, but I am not optimistic as apparently I have read from many here on EEVblog that they have a damaged transformer.

author: derZockerMP
author_rank: Regular Contributor
timestamp: October 22, 2024, 08:29:00 am
content: Hope you can repair it with that.Likely not, but we have one at work.I would recommend you test the transformer, but do not test it built-in. Disassemble it and test it externally on a Variac or AC source. Increase the voltage slowly and ensure the current is within range. Check the output voltage as well. Before the first smoke test, check the different voltage ranges on the board with ohms mode on a multimeter to ensure there are no shorts. Then you can connect the transformer.Please continue posting the repair, very interested in the processBest Regards