Auto-Reverse tape-deck problem

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I've just lent a friend an old Technics RS-T330R tape deck, which I used to make off-air recordings up until about 2 years ago, when I converted to using MD. Before I parted company with it I gave it a quick check-over. Playback was OK, using a tape recorded on another deck, with equal levels from both channels (as best you can judge using the deck's rather course metering) with the tape running in either direction. However, when you replay a recording made with the Technics itself, the left channel has recorded at a higher level than the right channel on side A, but this imbalance disappears when it reverses to record on side B.

I don't believe it can be a head alignment problem because playback is good, neither can it be a fault with the electronics of the 'Record' section of the machine, since it works fine on side B. I'm convinced it must be something to do with it being out of use for some time. On this deck the complete erase+rec/play head assembly rotates when you change tape direction - do the signals to and from the heads have to pass through some form of tiny commutator in there somewhere? Can anyone suggest what the problem might be please?
 
Hi
Try cleaning the heads with a soft lint-free cloth with a little iso-propanol or ethanol solution. If you haven't got either, try a little traditional non-flavoured, clear, uncoloured vodka - seriously, it's really only alcohol in water with little or no flavouring anyway.
Sometimes oxide from the tape can build up unevenly and possibly block one channel whilst recording.
Just put the cloth around your finger tip, dab a little alcohol on, and wipe the heads with your finger. Use a fresh area of the cloth to dry. It can be quite surprising to see a brownish deposit on the cloth when you believed the heads to be clean, even what appears to be a micro-dot of crud can have a dramatic effect on performance. Hope this helps.
Cheers
 
Hi Winchester

Thanks for your interest. I cleaned the heads with IPA & a cotton-bud before I powered the deck back up, as it had been out of use for such a long time, stored in my loft. Like I said at the start, there is not a problem on Playback, and Recording is fine too when running in the Reverse direction, so I'd convinced myself that the heads were clean and not magnetised. Does anyone know how the head-block on an autoreverse deck works, i.e. how is it driven around, and how do the signals get to and from the revolving heads? If someone out there has an exploded view of the internals of this type of head-block it might help me understand why it records unevenly.
 
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