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8512 to fix

Started by GeoffB17, 17:40, 16 January 23

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GeoffB17

I've got an 8512 that has been sitting in a cupboard for getting on for 30 years.

When tried, the screen showed signs of life, but the machine did nothing, the disk I tried to boot seemed to be viable, bit no sign of any disk access.   The drive lights were flickering.   The machine makes a fairly significant buzzing from the power supply.

I've now opened it up, it's wonderfully clean inside, looks almost like new.  I note the following:

A blue capacitor (ceramic, C5010) looks ill - leaking.   According to the circuit diag this cap is part of 'Protect Circuit'?  No other immediate signs.  Could this cap cause the buz, or has the cap been damaged by the real problem elsewhere?

Opened up the A: drive.  The belt is gone - hardly surprising - but from the state of the belt I think it had rotted in situ, and then been disturbed just recently, which suggests that the drive was getting both 12v and 5v.  So the power supply may well be functioning, apart from the buzz.   I can clean up and repl the belt, and see if it works/boots then.

Geoff

BUT - should C5010 be replaced first?   It's one of the 2kv rated ones.

GeoffB17

Further to my note above, the stuff on the cap that looks like it might be leaking might not be.   The stuff is white, and it nearly hard, and slightly rubbery.   The cap is right next to the STK3708 component, which uses some paste (same colour as the 'leaked' stuff, to link it to the big heatsink it's mounted on.  It could just be a well dried blob of the same paste?

What sort of fault could be causing the buzz?

Geoff

abalore

Probably it's just the drive belt.

GeoffB17

Hello,

Just to close this off.

My 8512 is now fine and fully working, drives cleaned and belts replaced.  The buzz seems to have vanished, i.e. it's not here.   It was certainly there at vendor's house.   I suspect something wrong with their elec wiring?

Geoff

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