Solid State Music V1B question
Richard.Cini at wachovia.com
Fri Jul 15 07:39:42 CDT 2005
I'm playing around with the SSM V1B video board in my Altair,
and I have a question about errata and board modifications, specifically
with regards to the +12v power supply.
I have three boards. One is "condition unknown" and two are working. The
+12v regulated supply consists of a small-value series resistor, a zener
diode and a cap. One of the boards has a 100 ohm, 1/4w resistor which is
charred and when operated, continues to smell. The other working board has a
220 ohm resistor and the same zener diode and appears to work fine with no
smell. The manual specifies a 100 ohm resistor and a 1N4742 diode.
The "condition unknown" board has a 7812 regulator soldered to the pads
replacing the resistor and the diode. From what I can tell from the
schematic, the +12v is used only for the character generator chip. When
turned on, I get a display full of well-formed garbage, which is probably
just that it's displaying the random data in buffer memory.
Does anyone have a view on what the best kind of repair might be?
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