Kevin LaHaie <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Hello
I have inherited a TR7/PS7/MN7 station, which was not working, but
rumored to have a power supply problem. Turns out it was the power
supply regulation board was shutting down the supply after reaching
about 4 volts.. By removing a feedback lead, the supply would regulate
to 13.5v. I replaced the key components on the board - the regulator
chip (NTE equivalent), a couple of transistors, a zener, resistor values
all check OK, so the problem is not the 723 chip, but some part of the
over-voltage protection function. It is not the is large clamping diode
that grounds the supply in case of a runaway, but somewhere in the
'feedback loop' to the 723.
2 Questions:
1. anybody have an idea what could be causing this? I have not replace
ALL the parts (yet!)
2. Does anybody know where to get a higher quality schematic scan - the
one I have is pretty 'muddy', with some voltages at key points on the
circuit being unreadable, which will no doubt lead me to the solution.
Thanks in advance to the members of a great list!
73 Kevin K7ZS
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