Repair Briefs - Vintage Computers

Ok, so these systems are rarely in tip top shape. But if you are a little bit inquisitive and go slowly, you can usually find the problem. You will say "Claude it's easy for you, you have many many years of experience as a technician and your also such an all around great guy too!"...Well thanks, but a lot of these repairs are just the fact of taking everything apart carefully, observation, and putting everything back in...

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This was a clean unit but had big problems with reading disks and formating on the internal floppy. Was simply slippage from the belt driven floppy drive. Watch out for dried out straps and belts in all old computer drives. Belt was some kinda weird width and size...I just put in something similar and tighter...have to make sure it clears the components around the belt's path. All ok for the 520 now...

I was so happy when I found a Adam for my collection. It came with many carts, the original joysticks...needed a lot of cleaning. Seller said it worked fine...Did he check everything? Nope. The digital tape drive these units have is a thing straight from hell. It's like a standard 4 track cassette but can't use the same tapes...Anyways, the cassette basic I got did not load, the tape drive did not move.

Opened up the Adam, took the tape drive out. Looked and saw that there was a small "flywheel" that seemed to check tape speed (?) by touching the tape and the other end of it's shaft had a encoder wheel with an optic attached to it. The rubber that was to make contact with the tape had dissolved and was now all into the encoder wheel, and shaft. Nothing would move. It was like taffy. Dissasembled the whole wheel, encoder (thin thin metal)...cleaned everything with alchool and put everything back...what would replace the rubber roller on the small wheel? I front tire from a slot car...yes...A perfect fit! Adam basic loaded on the 1st try. Now have a fully functionnal Adam in really nice shape!

Okay, so it's not vintage but still read on. This printer would only be able to go ONLINE after it had been powered up for 20-30 minutes. Hmmm....I got out the Freeze-It can and just went around...well I was actually an EPROM on the small board that holds the EPROMS on these units! It was intermittent...I had never seen this in all my years of fixing computer equipement and various stuff...So I just made a copy of the warmed up EPROM on an EPROM burner and the printer works fine now....the checksum was written on the original EPROM and it matched the new EPROM so all ok!

Was cheap at a garage sell. This is a great monitor to have for older/vintage systems because it goes from 15K to 31k in scanning frequencies and supports analog and ttl! They don't make them like that anymore. I use mine on my TRS-80 2000 that had that weird scan rate monitor...This repair was easy. An open coil in the blue gun drive circuit.. I don't have the specific part numbers anymore but it was just a fact of comparing the waveforms on the 3 colors on the neck board...An ohmeter showed the coil to be opened and a coil of similar value from an old modem board was what went in there...By the way, unless you know what you are doing you should not work into monitors. You can get killed by the high voltages in there...

The old Suns use this 48T02 chip with a lithium battery in a sort of "top module" glued on with epoxy. The battery is critical to system operation and if it fails, you wont be able to do much. The easy fix is replacing the whole chip assembly. I have been told it's around $20US plus the S&H and finding one...Well you can actually tap on a new battery to this chip if you are carefull and can solder a bit. See they way I did it (with photos) here.