Keithley 2001 - First Repair Attempt

[Tim51]

Hi Guys,

I have a first time Keithley 2001 repair. I'm following the repair process outlined here on xdevshttps://xdevs.com/fix/kei2001/.

I have not powered on the board. Only visual inspection and continuity testing.

The current primary fault suspect is C117 - This is an electrolytic capacitor on the secondary side of the main transformer and a part of the negative bootstrap rail. It has undergone a catastrophic failure which has resulted in a PCB charring and melted traces. See pictures below. I've continuity tested the entire area and am fairly confident I've identified the broken traces, see schematic mark up below.

My question to you all:

How should I handle this damage/repair?

Here is what I am thinking:

• Clean all the electrolyte spill with IPA.
• Remove built up charring to smooth out the surface a little. (This is questionable, comments welcome)
• Repair the traces with jumper wires.
• Replace the components then verify the repair connections with a continuity test.
• Confirm all the power rails are not shorted to ground or low resistance.
• Attempt a power up.

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[Tim51]

Having issues loading more than 1 picture at a time.  close_up.png (2752 kB. 1432x1058 - viewed 160 times.)

[Tim51]

 schematic_review.png (2487.82 kB. 1767x1170 - viewed 148 times.)

[picburner]

Don't just replace C117 only, all other electrolytic capacitors will probably be in the same condition, so you'll only do the board cleaning job once.
Regarding washing the pcb, the ipa alone may not be enough, you should do a pre-wash with de-mineralized water.
If you need an explanation of how the power supply section of the instrument works, you can find it here in a video by Ian Johnston, in the big brother k2002 repair tread.

[Tim51]

Absolutely, I've already removed all electrolytics and have replacements. Don't want to take any changes after this first repair. Hoping to have this unit running for years to come if this attempt is successful.

Thanks for the pointer. I'll certainly watch it. Been really enjoying Ian Johnston's repairs.

[IanJ]

Keep us posted on your progress. Always great to follow along.

Ian.

[eurgenca]

Isn't cr513 broken?

[Tim51]

Yes, it is broken as well. I’ve already got a replacement. My intent was to go over the major issue which was the capacitor failure.