mikiekimi
USAF Ret 1992 - 2012...Korea/OEF/OIF
Hoping someone can help give me some direction on getting this sorted out.
Picked up a Denon DP47F, first tonearm would not move at all when start button was pushed.
Replaced CDS 1,2,3 and now the tonearm moves, but it defaults to 45 RPM and drops the tonearm in the 17cm position.
I have pulled and tested TP1 & TP2 and both change resistance in the absence of light (these are the inside and outside photosensors).
I replaced TR13 and TR14 (they were 2SC458s). TR14s collector voltage should change to -5v for a 30cm record, but it stays +5v (this is what it should be for a 45 RPM single). C64 was also replaced.
Arm also moves to the 17cm position and defaults to 45 RPM WITHOUT a record on the platter (the sensors are not covered by the platter mat per the manual).
Voltages do not change on pin 17 or 18 of IC2 regardless of record size.
TR14s emitter is -5v, so the -5v 'rail' is present.
I haven't probed the resistors in the Position Detection circuit yet, none look burned up (I suppose one could be open but I'm not sure how likely that would be).
Seemingly nothing in the Position Detection circuit is changing based upon the size of the record on the platter. I'm guessing TP1 or TP2 changing resistance is supposed to trigger TR13 or TR14 to switch off/on given the size of the record on the platter, that does not appear to be happening.
Before I default to "it's IC2" does anybody have some secret squirrel knowledge on the 30/17 Position Detection circuit, and exactly what is supposed to be happening?
Picked up a Denon DP47F, first tonearm would not move at all when start button was pushed.
Replaced CDS 1,2,3 and now the tonearm moves, but it defaults to 45 RPM and drops the tonearm in the 17cm position.
I have pulled and tested TP1 & TP2 and both change resistance in the absence of light (these are the inside and outside photosensors).
I replaced TR13 and TR14 (they were 2SC458s). TR14s collector voltage should change to -5v for a 30cm record, but it stays +5v (this is what it should be for a 45 RPM single). C64 was also replaced.
Arm also moves to the 17cm position and defaults to 45 RPM WITHOUT a record on the platter (the sensors are not covered by the platter mat per the manual).
Voltages do not change on pin 17 or 18 of IC2 regardless of record size.
TR14s emitter is -5v, so the -5v 'rail' is present.
I haven't probed the resistors in the Position Detection circuit yet, none look burned up (I suppose one could be open but I'm not sure how likely that would be).
Seemingly nothing in the Position Detection circuit is changing based upon the size of the record on the platter. I'm guessing TP1 or TP2 changing resistance is supposed to trigger TR13 or TR14 to switch off/on given the size of the record on the platter, that does not appear to be happening.
Before I default to "it's IC2" does anybody have some secret squirrel knowledge on the 30/17 Position Detection circuit, and exactly what is supposed to be happening?
