I'm using a Nakamichi CR-1A cassette deck to save all my old cassette demos in ProTools. I noticed that I was getting some strange output out of the left channel of the deck. It's not the cables, or the cassettes themselves, or my Protools hardware. I've troubleshot and concluded that the issue is definitely the deck. I have the same problem from the line-outs and the headphone output. The signal from the right side appears just fine. The signal from the left side appears to have reduced amplitude on one side of the waveform. Please see attached photo. The response I got from a friend of a friend was that the problem is "the failure of the positive side of the DC PSU or OP amp, on the left Channel , old common problem in analogue. No way to fix it, digitally. He needs a new machine." I don't know what this means, and getting in touch with this person to elaborate is not an option. I was hoping someone here could help me shed some light on this problem, and hopefully offer a solution to fix the deck rather than ditching it altogether. Many thanks!

I think your friend is right.
The problem channel is running out of positive "headroom".
That could have several causes. Positive supply, DC offset (caps), etc.
To fix, it will need surgery.
Easy for a tech (with a schematics diagram).
Leo..

Thanks, Leo. I do have the manual, but the manual does not have a schematic diagram. It's a 25 year old deck, so that could be hard to track down.

Hi.
Just thought of something.
I have fixed many cass decks, and I remember that sometimes you have playback problems because the rec/play switch is oxidised.
Put a blank tape in it, and exercise the play/record function 20 times or so.
It might spring back to life.
Leo..

I tried your suggestion, Leo, but it didn't work. Thanks anyway...

Your friend and LeeYoo are right on target.

Asymmetrically limited output (which is what you have) on one channel only, indicates that it's an amplifier or op amp problem and very likely NOT a power supply issue (the PS would be common to both channels so would affect both channels).

It may be a op amp that has gone bad, but may also be a leaky or shorted coupling capacitor that has drastically shifted the bias in a playback amplifier stage. It's not that unusual to see bias shifts in older gear as caps age.

It's difficult to do without a schematic, or at least some experience testing audio gear, but a point-by-point measurement of the DC voltage levels on each stage (op amp outputs or single-ended transistor stage collectors) comparing the DC voltage on the bad left channel to the identical circuit point on the properly working side will show you where the offset is occurring. Testing with a DC-coupled oscilloscope would be even faster.

Unless you have the tools and skills, it's a trip to a qualified tech. Unfortunately, it may not be financially viable to repair. (Might cost more than just purchasing a new deck.)

Thanks so much to everyone for your feedback! Lotus 7 and Leo, how many labor hours do you figure it'll take a tech to fix it with a schematic? What about without a schematic? I now have to decide whether or not it's worth the money to get it fixed. Thanks again!

Orange Cap Disease
What is it?
Orange Capacitor Disease is unofficial name given to the failure of little orange metalized polypropylene capacitors that are used in many Nakamichi tape decks. For some unknown reason these capacitors are very prone to failure and usually result in rustling, crackling or lack of audio in one, or sometimes both channels.

Found this on this site:Scott's Nakamichi FAQ Page