On Fri, 23 Jun 2006 00:27:31 GMT, Tim Phipps
put finger to keyboard and
composed:

Ok I had a good look over it again today and I'm pretty sure that this
deck does not have a mechanical record/playback switch. The only
switches on the board are those for selecting the tape type and Dolby
NR. It would seem that it is done electronically although there are
very few ICs on the board - mostly discrete components. As it happens I
do have a scope that I acquired for free but I don't think I have much
chance of obtaining schematics as it is a fairly old unit - appears to
be made around 1983 going by the dates marked on the motors.

Just to check the head for sure I tried reversing the connector that
goes to the board since it is wired symmetrically. Sure enough I got
the same result - playback only on the left channel, although this time
the signal being supplied from the right output of the head. This seems
to confirm that the head is good and unfortunately it's an electronics
fault. However, I did try a test recording and it records on the left
channel only. I checked by playing back on a known good tape deck. If
I turned up the volume on my hifi amp much higher than normal listening
level with the balance control all the way to the right I was able to
hear a faint signal. So it seems that it is a fault on the board which
is affecting both playback and recording.

If there is any obvious symmetry between the left and right channels,
I'd be playing a test tape (eg 1kHz sinusoid) and scoping the
equivalent points in both halves of the circuit. Otherwise, if the
signal disappears inside some R/P processor IC, I'd download its
datasheet and hope that Pioneer's design follows the application
circuit.

- Franc Zabkar
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