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8753a phase lock lost error after warm up

Question asked by jtvdude on Mar 7, 2008
Latest reply on May 5, 2008 by jtvdude
Hi all.
I have a 8753a that after about 30 to 60 min get a phase lock lost error.
The tune voltage on the A13 bd  goes from varying  to a steady 13.78 volts. It will only reset after being unplugged over nite. AT TP2 I see spikes that coresspond with failure. Tp 5 also has the spikes.   I have chked and replaced U7 U2 Q4 .  When unit is working all chks and performance are fine  non are out of tolerance. the voltage starts to climb and locks at 13 volts. I need some help to try an isolate what board it is on. i have the schematic and service mnauel  but  it seems this error is not fixed by anything i have seen in the manuel.  
thanks   Jim