Recent score: CBM 8032

--- JP Hindin <jplist(a)globe.net.nz> wrote: Fun. Perhaps. The PSU is a linear one, easy to fix. The transformer needs to be putting out ~18VAC-22VAC to the twisted pair of brown wires going up to the monitor. I don't know the exact voltages of what goes onto the motherboard, but there are a pair of +5VDC regulators in the heat sink, plus, IIRC, +12V and maybe some extra goodies, too (4116s are multi-voltage). If you don't get a decent amount of AC voltage to the monitor, or if you don't see +5V on the expected corner pins of the TTL chips, you have a PSU problem. Look for oxidation/discoloration of the PSU connector where it attaches. Too much current draw causes the connector to break down, resistance increases, causing more current draw - rinse, repeat. I've seen some of the plastic PSu connectors blackened and blistered. Yes. If you _do_ have all the right voltages, try reseating all the connectors and socketed chips. Barring that, anything from a bad ROM (yes, I've seen that happen) to a bad CPU could cause things to go wrong. I happen to have test clips from a Commodore dealer, so I can use them. An oscilloscope can show that the CPU is clocking along - with a spare CPU chip, you can bend out the data pins and short certain ones together to cause all reads to return $EA - the NOP opcode - The CPU should fetch the reset vector ($EAEA) and begin executing from there... The idea is you mangle up a CPU, then watch the address lines strobe up to show how various parts of the board are working. It helps identify stuck bits and bad selector logic. If necessary, I could photograph one that I received from the local C= dealer when they closed and I bought out the service department (10 years ago). Schematics, firmware, etc., are available at ftp.funet.fi. Yep. Don't let the top fall on you. Trust me. -ethan __________________________________________________ Do You Yahoo!? LAUNCH - Your Yahoo! Music Experience http://launch.yahoo.com