On 11/7/2012 5:18 PM, Charles wrote:
I fired it up today and no joy. Took off all the covers/shields and
tested all the fuses and still no joy. Reseated all the connectors and ICs.

Finally, after repeated power on/off cycles it started to work.

Any ideas? I need this generator for an important project but can't rely
on it now. Any suggestions?

Thanks!
Assume the first thing you did was test it in another mainframe?
Or at least moved it to another socket in the same mainframe?
I also assume that you have something else in the mainframe so you
can rule out a bad power switch or corroded fuse holder or any
other common stuff.

The FG507 post-dates my tenure with TM500 engineering.
It's been 35 years and I'm OLD...so much of what I'm about to
say may be correct...maybe...YMMV.

The mainframe supplies unregulated DC.
~7V intended to be regulated to +5.
+/- 20ish intended to be regulated to +/-15V or so.
Because of the wide line voltage specs and cross loading,
it's difficult to get more than +/-15V regulated under worst
case conditions.

There are two floating transformer windings per hole. You can
get +/-20VDC if you're careful with the rectifier and regulator
design.

Each hole has one NPN and one PNP transistor allocated to it.
These are often used as pass transistors for power supply regulation.
I believe that all TM500 stuff of this era had linear regulated power
supplies.

A common failure is that the mainframe pass transistors come unsoldered
at the backplane board and become intermittent. Some plugins run them
hot, so the transistors themselves can become intermittent.

FG507 schematic doesn't seem to be available, but almost any TM500
signal generator from that era will have a similar power supply topology.
The tm503 manual has all the mainframe parts and pinouts.