Monitor 41 Dead after 4 years storage

[olduhfguy]

I'm trying to resurrect a once-working Monitor 41 (K-1) that was put in storage in working condition. However it is now DOA, no display, no nothing. I downloaded looked at the 441 manual on this site, and unfortunately there are several differences with the main PCB - There is power getting to PCB, +5v and +12v are OK, fuses are OK, connectors seem to be OK, just nothing happening on display at all.

There is K-1 feeding the unit-I pulled the filter and it looks fine, I would think that even if there was something major wrong with a mechanical or electrical part I would at least get something out of the display.

I'd like to think I've missed something obvious, can someone get me back on track.

[hawkins111]

M41 power problem

We have to assume the fuses are good?

If you have a Volt Ohm meter, you can check the transformer. The H connector should show 17 Ohm’s, the L connector 824 Ohm’s, and the M connector 1.3 Ohm’s. That will prove the transformer. If that is OK you need to look into the indicator circuit, particularly the On/Off switch.

Keep us posted,

Tom

[olduhfguy]

Update on Monitor 41 problem-

Well, it looks like more than a problem with transformer/connections - I checked the voltage regulators on the pcb, and I have the +5 volts and +12 volts going to the circuitry. I have put an oscilloscope on the cpu lines, and I can see that the clock is running, but there doesn't seem to be any I/O occurring on any of the ports. I made sure that the reset line wasn't pulled down, but I don't have the correct schematic for the 41, just the 441 schematic and unfortunately it's different enough that I'm stumped. Does anyone out there have the schematic to the 41 ? If so I'd sure like to have a look at it. Thanks -