RTR Technics RS-1700 does not record left channel

[leopardus2]

I have this RS-1700 which does not record on the left channel, in either directions. Right channel works fine...
If I turn the input knob to the max something gets recorded, but at a very very low volume.
Where should I look? Do you think the left channel recording switch could be the culprit? The tape appears to be erased just fine...

Thanks in advance
Rick

[Des_Lab]

The first two things I would look at are: the tape path. Is there a clump of oxide on the head that might be preventing it from making snug contact with the tape? You'd be surprised at how little of a clump it can take to render a head useless. A Q-tip dipped in 99% alcohol (or other cleaning solvent) will do the trick. The other thing I'd look at would be your input pots. Often times, over the years, dust, fingerprint oil, and other contaminants can work their way into them as you turn it up and down. It may have finally gotten to the point that the contacts are breached and not making good contact. Try removing the outer knobs and squirting some contact cleaner in there and give it a good wiping and twisting. That might do it.

If neither of those work, then that's a much deeper issue and will likely involve 'surgery' on the deck.

--------------------------------------------------------------------------
DL-potshot

[jblmar]

Try switching the Bias & EQ switches while recording. An intermittent switch here will effect recording.

Ron

[leopardus2]

The first two things I would look at are: the tape path. Is there a clump of oxide on the head that might be preventing it from making snug contact with the tape? You'd be surprised at how little of a clump it can take to render a head useless. A Q-tip dipped in 99% alcohol (or other cleaning solvent) will do the trick. The other thing I'd look at would be your input pots. Often times, over the years, dust, fingerprint oil, and other contaminants can work their way into them as you turn it up and down. It may have finally gotten to the point that the contacts are breached and not making good contact. Try removing the outer knobs and squirting some contact cleaner in there and give it a good wiping and twisting. That might do it.

If neither of those work, then that's a much deeper issue and will likely involve 'surgery' on the deck.

--------------------------------------------------------------------------
DL-potshot

Thanks for your suggestions.
I have cleaned and demagnetized the heads, so that is obviously not the problem.
Also, it happens on both forward and reverse head.

I will try the pots thing, but if it was the pots, I believe I should also have the problem when listening to source, but that works fine...

Rick

[leopardus2]

Try switching the Bias & EQ switches while recording. An intermittent switch here will effect recording.

Ron

Tried that. Also squirted contact cleaner in there...

Thanks

Rick

[jblmar]

Check the head wiring. If that's not the problem, check the record relay contacts. One side works.


Ron

[leopardus2]

Check the head wiring. If that's not the problem, check the record relay contacts. One side works.


Ron

the 1700 has separate heads for fwd and reverse, both show same issue, so it is unlikely that it is a head wiring problem. I will try to dismantle the unit to check connectors, but it is not an easy job as far as I have seen...

Thanks
Rick

[jblmar]

I would still check the record relay. You'll need an oscilloscope to 'see' if a signal is present at the common post of the relay. If not, you have a record amp issue.

Ron

[leopardus2]

I would still check the record relay. You'll need an oscilloscope to 'see' if a signal is present at the common post of the relay. If not, you have a record amp issue.

Ron

I have not located the record relay yet. Isn't it supposed to be sealed? How can dirt go in there?

Thanks again
Rick

[jblmar]

I live 1/4 mile from the Atlantic ocean. Relay and other contact intermittents are a real problem.
The relay has a top cover that can be removed so it really isn't 'sealed.' Even if it were, the spark created on the 'break' is enough to form carbon deposits and pitting. Same sonic result as a oxidized contact.
Don't confuse the realy closing as an indication that the realy isn't the problem.
Checking the common terminals of the relay (left and right channels) will give you a good indication of where the general problem is. If the signal is present at both common posts, the problem isn't the relay it's futher back.
If your DMM has a frequency counter function and you have access to a tone generator or a CD with test tone on it, you can record the tone on your deck. You can check for the signal on your DMM.

Ron