I have a RCA PTK169PGA RPTV that I have been working on and it has been a
real dog. I can finally get the TV to come on, the audio is fine, but I do
not have full deflection in either the vertical or horizontal direction and
the convergence is way off. I have found that at "stand-by" I have a B+ of
143.4V and I have the 13.6V on the cathode of CR4118, 6.6V on CR4117 and
24V on CR4119. I also have the +5V "stand-by". When I turn the TV on, the
B+ drops to 114.5V and the 13.6V drops to around 11V. I decided to take
this chassis out of the cabinet and disconnect all the boards to see if I
could fix this using the 100W light bulb trick. Here is what I have done:
I completely isolated pin 1 of the HV Xfmr (T4401) so now the sweeps circuit
and the HV transformer is out of the circuit. Next I placed a 100W light
bulb across the B+ 143.5 Rail. Then I plugged the TV in without any of the
other boards attached. At this point I am simply trying to figure out why
the B+ is being loaded down. I have the light bulb in a switched socket, so
when the Light bulb is switched off I have all the proper "stand-by"
voltages and as soon as I switch the light bulb on, the light bulb flickers
off and on and therefore the B+ is not coming on at all. The problem has to
be either in the chopper circuit or the feedback circuit for the B+. I have
already replaced the following: U4101 (Chopper IC), C4104 (15uf cap off pin
8 of chopper IC), C4102 (2.2uf cap off of pin 6 of chopper IC), C4108 (39uf
cap to the base of Q4101), CR4116 (B+ diode), CR4118 (13.6V didode),
C4141(470uf cap on the B+ rail), and the following transistors in the
feedback circuit: Q4105, Q4111, Q4106, Q4109, Q4107. I'm just trying to get
the B+ to stay up when the TV is plugged in without any of the other boards
attached and when I have a 100W light bulb on it.

This B+ should come up with the load on it right??????

Thanks!