david winter
Classical music lover.
Hi,
I have some difficulty repairing a Mitsubishi LT-5V vertical linear tracking turntable.
I replaced one of the two photodiodes (broken) in the tracking servo assembly using a TEMD6200FX01 carefully installed and positioned above the light bulb.
I need to know how to make the electrical adjustments, especially VR-201 (IC103, NEC C4558) and VR-202 (IC104, NEC C4558), which are not explained in the service manual. Right now I have the same voltage on pin 1 of IC104 whatever the angle of the tonearm. IC104 receives the signal from the replaced photodiode.
The voltage at pin 1 of IC103 changes if I move the arm (the photodiode is original).
I guess the mechanical adjustment of the lateal screw which positions the black assembly holding the two photodiodes is made by observice the same level at both diode outputs, but what if both diodes differ ?
I also had to replace Q145 (2SC360) by a 2SD880. This one heats a lot (I can barely touch it) despite correct output voltages. Another 2SC880 gave the same results. Its emitter current is 250mA or so, so I wonder if the 2SC880, which is a known replacement for the 2SD360, is really suitable in this case.
Any advise appreciated. Thanks !
I have some difficulty repairing a Mitsubishi LT-5V vertical linear tracking turntable.
I replaced one of the two photodiodes (broken) in the tracking servo assembly using a TEMD6200FX01 carefully installed and positioned above the light bulb.
I need to know how to make the electrical adjustments, especially VR-201 (IC103, NEC C4558) and VR-202 (IC104, NEC C4558), which are not explained in the service manual. Right now I have the same voltage on pin 1 of IC104 whatever the angle of the tonearm. IC104 receives the signal from the replaced photodiode.
The voltage at pin 1 of IC103 changes if I move the arm (the photodiode is original).
I guess the mechanical adjustment of the lateal screw which positions the black assembly holding the two photodiodes is made by observice the same level at both diode outputs, but what if both diodes differ ?
I also had to replace Q145 (2SC360) by a 2SD880. This one heats a lot (I can barely touch it) despite correct output voltages. Another 2SC880 gave the same results. Its emitter current is 250mA or so, so I wonder if the 2SC880, which is a known replacement for the 2SD360, is really suitable in this case.
Any advise appreciated. Thanks !