9 May
2017
9 May
'17
7:29 p.m.
Am 09.05.2017 um 18:10 schrieb Jon Elson <elson at
pico-systems.com>:
On 05/09/2017 08:26 AM, Philipp Pap via cctalk wrote:
OK, I just read in the service manual
?The power supple is a switching type dc supply incorporating a pulse-width modulator
(PWM).?
but I don?t know the meaning on the drawing ?+5V ref? ?vcc? ? POWER ON ??~RESET , HALT,
RESET?
Could that mean that the problem could be in this ?POWER ON? block logic???
Thanks again!
Anyhow, now I have 41 and 83 Volts at the 42 and
85V test points,
but always 0 Volts at the +5,-12,+12,+15V test points.
The fuses are good and the secondary transformer seems good as well.
Does this have a switching power supply for the logic (5, 12, 15V) or is it a
rectifier/filter/regulator off the transformer?
If rectifier/filter/regulator, it seems odd that FOUR voltages would quit at once. So,
I'm guessing it might have a switching supply for those voltages. It sounds like the
regulation circuit failed (display got brighter) and then a crowbar circuit tripped to
shut it down. Unless you are pretty skilled, switchers can be a bit hard to troubleshoot.
It might be easier to get a supply with the needed voltages and just patch it in.
Jon