[TechAssist] RCA Proj. Model P56740BG Chassis PTK178L2P. Red convergence problem, repeat damaged - R7077, R7069
- From: "Robinson Electronics" <RobinsonElectronics@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 14 Apr 2005 12:04:55 -0400
Can any of you RCA Techs. help us with this set?
Customer originally had a convergence problem - bowed in red (top & bot) of
picture.
I found these resistors burnt, R7077U - 2.2 ohm, R7079U - 1 ohm, and "burnt
bad" R7069 .25w 36 ohm next to Q7019 -small pnp transistor marked 1101-01A,
I replaced Q7019 with a sub NTE288, showed to be a good sub.
I replaced all the resistors that checked bad locallized to this end of the
board.
I checked all 4 of the transistors on this heat-sink - looks like
Q7021 retrace boost - NPN (checks good)
Q7022 top output - (darlington checks ok in ?) with meter
Q7023 bottom ouput - (another darlington checks ok ?)
Q7024 retrace boost - PNP (found shorted) Marked F15031 showed to be Mfr#
238997 replaced it.
After installing, same problem (red bowed in from top & bottom) and saw a
slight puff of smoke in back from same resistors that burnt before.
Considered trying to order the whole board, but showed not available from
Tritronics.
Can anyone help me with this, or has saw this before?
Not sure of what else to order and try next, (I guess maybe I should order and
relace both darlington's and both retrace transistors) next?
I would appreciate it very much. Thanks. David.
Robinson Electronics
1075 Sweeten Creek Road
Asheville, NC 28803
Ph./Fax. 828 274-3787
Toll Free. 1-888 ROBELECT
www.robinsonelectronics.com
www.robelect.com
Mailto: RobinsonElectronics@xxxxxxxxxxx
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