Mac Classic corpse

#1 Tue, 3 Nov 2009 - 10:25 68kMLA

The machine (240 V Classic - not II) has not been switched on for about 4 years and appears dead. I have opened up and can see the voltage on the inside of the mains switch but I can see no voltages at all further down the line, e.g. on the 14-pin connector to the motherboard. The fuse is OK. My impression is that something basic is wrong with the Analogue/Power Board. I can't see any burn marks or spewing capacitors (it looks very clean inside) and wonder if it is something simple. What could I do to diagnose the problem?

Grateful for any help,

Crane

#2 Tue, 3 Nov 2009 - 11:28 68kMLA

What does it do when you turn it on?

#3 Thu, 5 Nov 2009 - 12:06 68kMLA

When I switch on absolutely nothing happens, no sign of anything working. That's why I checked that the mains voltage could be seen on the inside of the switch. Hence the word 'corpse'.

#4 Thu, 5 Nov 2009 - 14:14 68kMLA

What could I do to diagnose the problem?

get a volt meter and start tracing voltages until it stops

#5 Sat, 7 Nov 2009 - 19:33 68kMLA

get a volt meter and start tracing voltages until it stops

Careful there, special high voltage probes may be called for in some areas.

#6 Wed, 18 Nov 2009 - 17:00 68kMLA

A circuit diagram for the analogue board of the Mac Classic would be a great help in tracing voltages. I can find one for the Mac SE on the web but not the Classic. Any suggestions?

#7 Wed, 18 Nov 2009 - 17:55 68kMLA

The classic/II seem to be difficult to find info on. When I was killing mine I could not find too much info.

#8 Wed, 18 Nov 2009 - 19:56 68kMLA

The classic/II seem to be difficult to find info on. When I was killing mine I could not find too much info.

Contrary to Mars478 post, Larry Pina's Mac Classic Repair and upgrade secrets, readily and affordably found around the internet, is an extremely useful quide. In particular, one passage caught my attention about no power. He recommends checking resistance across RP2 surgistor from the solder side. It should read 12 ohms. If 0, then desolder, reshape the leads and resolder.

Also if you do want schematics, Bowmarc has a set of reasonably priced Classic reverse engineered schematics (click computer, then search for "classic").