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Re: [N8VEM-S100:766] Advise on restoring old boards

I'm with you almost to the end -

After cleaning, do a careful visual once-over with magnifying glass, checking for shorts, bad traces, broken, burnt or damaged components, etc. Take a careful look at electrolytic caps for bulging or leaking.

Before powering up, do a short-test with your ohm-meter and make sure you don't have anything shorted acrosss the power - ground rails. I've also wired up a spare S100 connector with +5, +12 and ground and hooked up to current-limiting bench power supply. I use that for a first power up to make sure current draw is within sensible limits. I also prefer the Caig Labs DeOxit for contact cleaning and lubrication - use it on both card edge and socket.

And don't lean over the board for first power up, in case you have a tantulum cap waiting to launch.

Good luck!

From: John Monahan <mo...@vitasoft.org>
To: "n8vem...@googlegroups.com" <n8v...@googlegroups.com>
Sent: Thu, March 22, 2012 3:57:31 PM
Subject: Re: [N8VEM-S100:766] Advise on restoring old boards

All fine Don in fact somewhat overkill. Do not clean the s100 pins with an eraser that actually removes a layer of gold. Some old boards had very thin layers. Instead use "TVtuner cleaner" radio shack at least used to have it. IC's  last for ever as do resistors and LED's on storage. Caps sometimes fail. Might consider replacing all except the 0.1uf filter caps. Sockets are another story definitely need to pull out chips and wipe pins check for corrosion reseat. 
Good luck

Sent from my iPhone

On Mar 22, 2012, at 4:35 PM, Don Caprio <ilv...@gmail.com> wrote:

I recently won an IMSAI front panel board on eBay. Just received it in the mail today and
boy is it in bad shape. Looks like it was sitting around unprotected for the last 25 years.
Could of even been outside.

I'm curious how some of you would go about restoring this board. All of the LED and capacitors
were bent over. Some caps are chipped and cracked. I was able to straighten out the LED's without
breaking any pins (hopefully). The top of the board has a thick film of dirt and grit. All of the IC's
are socketed.

Here's my plan of attack:
  1. Brush down the board with a clean paint brush and remove all the lose dirt.
  2. Blow the board off with an air nozzle from my compressor. The compressor does have a oil and water filter.
  3. Immerse board in a PCB cleaner solution and scrub with a tooth brush
  4. Remove all of the IC's (Can't remove the 8255 without unsoldering two switches).
  5. Do another board wash.
  6. Clean S100 connector with pencil eraser to clean up contacts.
  7. Insert board in backplane and test the 7805 voltages. Replace if needed.
I was considering replacing all of the LED's, filter capacitors and voltage regulator.
I'd really like to remove the 8255 socket and replace with a low profile socket.
The current socket is preventing the two switches from lining up with the others. They stick up about 1/32 of an inch. The switches are resting on the 8255.
I'm a bit nervous about unsoldering and replacing components not knowing what sort of abuse the traces can take.

Your words of wisdom and experience is greatly appreciated.

Don Caprio