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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Viewsonic 21" P815 -2M G3 chassis Monitor clicks clicks clicks. Schematiclink also
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 we 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 |
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