C
Chris Mares
- Jan 1, 1970
- 0
I have a View sonic P815-2M G3 chassis that had no display after turning
it on one day.
Before I started working on it the symptoms were: Power on , power led
is green, relay clicks on, then degauss noise is heard, relay clicks
off, power led goes amber,...then the process repeats continuously with
no display at all.
I have attached a link to a zip file with jpeg schematics to aid in my
diagnostic.
http://members.cox.net/scridmares/p815.zip
After some initial troubleshooting I found Q876 on mainboard open.
(circled on jpeg 59) I replaced it and this made no change to symptoms.
Further troubleshooting led me to another open Q674 on the EHT board
(circled on jpeg 37) so it was replaced also.
Now when tested the monitor will stay in powered led green mode, as long
as an input signal is present but I still have no display. Also the
degauss function has stopped cycling and the clicking relay sound has
become more rapid. When the relay clicks on I can hear about one second
of static build at the EHT board but still no display. The Flyback
almost seems to let out a brief squeal for one second then the relay
cuts out and the process repeats. Two large arc snap sounds came from
the case also, but I couldn't tell from where before they quit. I have
found excessive voltage at ribbon cable supplying EHT board that should
be 195 volts but measures 232 volts. (jpeg 38)
The voltages at base of my HOT are only about 2 volts at best. From what
I make of the schematic I am suppose to have 28 volts there but I seem
to be losing it after T541 (circled in green jpeg 59).
I am guess that the power supply is shutting down due to the over
voltage of 232 volts? I guess my next step would be to get my hands on a
variac to see if I can get it to fully power up by varying the line
voltage. Does this sound like a good next step?
Any help with this is really appreciated as I haven't had my hands into
ant circuits like this since high school.
Thanks
Chris
it on one day.
Before I started working on it the symptoms were: Power on , power led
is green, relay clicks on, then degauss noise is heard, relay clicks
off, power led goes amber,...then the process repeats continuously with
no display at all.
I have attached a link to a zip file with jpeg schematics to aid in my
diagnostic.
http://members.cox.net/scridmares/p815.zip
After some initial troubleshooting I found Q876 on mainboard open.
(circled on jpeg 59) I replaced it and this made no change to symptoms.
Further troubleshooting led me to another open Q674 on the EHT board
(circled on jpeg 37) so it was replaced also.
Now when tested the monitor will stay in powered led green mode, as long
as an input signal is present but I still have no display. Also the
degauss function has stopped cycling and the clicking relay sound has
become more rapid. When the relay clicks on I can hear about one second
of static build at the EHT board but still no display. The Flyback
almost seems to let out a brief squeal for one second then the relay
cuts out and the process repeats. Two large arc snap sounds came from
the case also, but I couldn't tell from where before they quit. I have
found excessive voltage at ribbon cable supplying EHT board that should
be 195 volts but measures 232 volts. (jpeg 38)
The voltages at base of my HOT are only about 2 volts at best. From what
I make of the schematic I am suppose to have 28 volts there but I seem
to be losing it after T541 (circled in green jpeg 59).
I am guess that the power supply is shutting down due to the over
voltage of 232 volts? I guess my next step would be to get my hands on a
variac to see if I can get it to fully power up by varying the line
voltage. Does this sound like a good next step?
Any help with this is really appreciated as I haven't had my hands into
ant circuits like this since high school.
Thanks
Chris
