27 Apr
2002
27 Apr
'02
6:40 p.m.
Louis Schulman wrote:
I am putting my SWTPc 6800 back together, after complete disassembly
for cleaning. So, on to testing the power supply.
It works! But here's the question, which I know has been discussed
before with respect to S-100 machines.
The power supply is a big transformer with one really big (91,000 ufd)
capacitor, and the usual rectifier stuff, etc. The documents call for
7-8 volts unregulated, along with + and - 12V.
I am getting something like 9.3 V, and + and - 14.3 V. Are these
voltages too high? Of course, on the SS-50 and SS-30 cards there are
voltage regulators, but I don't want to cause any damage. This thing
probably hasn't been powered up in 25 years.
How can I check the capacitor function without an oscilloscope or other
fancy equipment? Should I worry about "reforming" the capacitor?
Thoughts appreciated.
Louis
Shouldn't be a problem, as S100 cards have onboard regulators to get +5,
and +/-12. Only problem there is that the regulator transistor will be
dissapating a bit more power, so have a fan on the card cage if
possible. The heatsink should run warm to the touch, and if it it is
too hot to comfortablly hold for several seconds, then you may be in
trouble. Any excess heat means a premature death for solid state
electronics.
You might look at the cards and inspect the regulator circuitry. a
darkening of the pcb underneat the heatskink is normal, but if the
traces seemed to be crispy crittered, ya got problems, or will have
probs very soon.
Gary Hildebrand
ST. Joseph, MO