I'm working on an M4868 Apple Studio Display, 21" Trinitron tube, (the Blue & White pod style enclosure) which has a horizontal deflection problem, and I could use some advice.
Picture is squashed horizontally to about 1/4 normal width, centered in the screen. The image has some mis-convergence, but is otherwise stable and legible, so I'm presuming that HV & vertical deflection are OK.
Upon disassembling it, I found a blown capacitor (open) on the "deflection" board (this board contains both H & V deflection & the FBT). The solder on one lead had disintegrated, and there's significant heat discoloration on the circuit traces either side of the solder pad.
Is anyone familiar with the circuits of this monitor? I don't have and can't find any schematics for this unit, so I'm not entirely sure what circuits the components belong to:
The blown cap is CL9 (WIMA FKP1 5200pf 1600vdc/650vac high current polypropylene film). It bypasses the collector of transistor QL23 to ground. QL23 is a BUH1215
Problem is, I can't find a 5200pf replacement. Is this value critical? Would a 4700 or 6800 pf work as well? If not I'll have to parallel multiples to get 5200.
Is it likely that the cap failure would have taken out QL23? or any other component? CL9 was easy to remove, but QL23 would be a bear.
And finally, there was a resistor (RL173, .24 ohm, 3W wirewound) hot glued to the top of cap CL9. Is this a required thermal coupling? (RL173 is NOT part of the CL9/QL23 circuit).
Any help appreciated, thanks, Sean