J
Jim Candela
Guest
Hi Group,
This is my first post with this group, so be kind!
I have a busted oscilloscope. This one is a factory modified
Phillips/Fluke PM3050. The scope was running in a warm environment 5-10
years
24/7, and it sure seems that every electrolytic with the Phillip logo is
open circuit, and
weightless! These capacitors lost their juice! One shorted and exploded.
Anyway after replacing three
shorted diodes, a power fet, blown trace, burned AC line Molex connector,
and 6 capacitors I got it powered up, and with a trace. Not bad, but the
power supply is making audible noise (maybe 200hz), efficiency is low (hot
fet heatsink), and the trace has modulation from what I presume is power
supply ripple. It could be the Anode voltage varying around. I am at the
point where troubleshooting without a schematic
is getting to be a pain with a lot of guess work. I looked at 3 P/S outputs
+12, -12, and +10. These all are clean and stable. I need to replace more
capacitors I know, but I was hoping to find a diagram to help me isolate
what is going on with the switching off line power converter. There is a HV
transistor, and a power fet sharing the same heatsink, and they seem to be
in series. The fet and a high speed diode were popped.
If any of you fine folk have the power supply schematic, could you scan in a
copy for me ? I am mostly interested in the power supply PCB.
Thanks in advance!
Jim Candela
WD5JKO
This is my first post with this group, so be kind!
I have a busted oscilloscope. This one is a factory modified
Phillips/Fluke PM3050. The scope was running in a warm environment 5-10
years
24/7, and it sure seems that every electrolytic with the Phillip logo is
open circuit, and
weightless! These capacitors lost their juice! One shorted and exploded.
Anyway after replacing three
shorted diodes, a power fet, blown trace, burned AC line Molex connector,
and 6 capacitors I got it powered up, and with a trace. Not bad, but the
power supply is making audible noise (maybe 200hz), efficiency is low (hot
fet heatsink), and the trace has modulation from what I presume is power
supply ripple. It could be the Anode voltage varying around. I am at the
point where troubleshooting without a schematic
is getting to be a pain with a lot of guess work. I looked at 3 P/S outputs
+12, -12, and +10. These all are clean and stable. I need to replace more
capacitors I know, but I was hoping to find a diagram to help me isolate
what is going on with the switching off line power converter. There is a HV
transistor, and a power fet sharing the same heatsink, and they seem to be
in series. The fet and a high speed diode were popped.
If any of you fine folk have the power supply schematic, could you scan in a
copy for me ? I am mostly interested in the power supply PCB.
Thanks in advance!
Jim Candela
WD5JKO