Cassette tape speed problem

[GOYA]

The unit is a Nakamichi Cassette Deck 2. I just replaced the capstan motor. The belt seemed to be fine. I get speed fluctuations and weirdly, if I lift up on the corner of the deck, the speed goes back to normal (possibly normal but definitely better than before I lifted). So it seems there is some mechanical stress involved in the problem. I suppose the lift might be tightening up the belt a hair? I failed to clean and lubricate anything so that might come into play. The motor isn't exactly top notch (Chinese Mabuchi knockoff) but I can't see a crap motor changing speeds because the deck's case is lifted.
Anyone seen this before?

edit: now that I think about it, I remember a cassette deck that would only work if it was upside down. No idea what that problem was.

 

[Hajidub]

I wouldn't have changed the motor with a cheap Chinese knockoff, without changing the belts (cart before the horse). Order of cassette deck repair I've learned from AK: belt, idler, then other stuff.

 

[vwestlife]

Maybe a cracked solder joint or trace on the motor's circuit board? Sometimes when you buy these motors from China, they ship them in a plastic bag with no padding, which is a great way to get them damaged in transit.

 

[GOYA]

I just finished cleaning and applying some Rubber Renue. It's apparent that the belt is slipping. There's definitely tension but just not enough.

 

[GOYA]

More cleaning, oiling and a new belt. The big fluctuations in speed are gone but flutter is terrible.

 

[Hajidub]

W&F are a result of speed. Flutter in particular has to do with slow speed and possibly angle of tape path. Goya, why not put the original NAK motor back in this thing and buy a good belt for it?

 

[GOYA]

The original motor was dead. That was the reason for all of this. I now have 2 dead SHE2L motors (the original in this deck). If anyone has any insight on repairing these Sankyo motors, I'd appreciate the advice. The belt is a PRB FRX6.7. Is there a better belt available?

 

[Hajidub]

Copied wrong link, sorry.

Also on tapeheads one of the resident NAK experts claimed the only FRX6.7 belt that didn't give him w/f were the Marrs belts (business rating not that great recently). He opted for:

As listed in the PRB catalog, that belt is 6.7" long and .2" wide
Unfortunately, the PRB belt of that size (FRX6.7) will cause a huge amount of wow/flutter. Don't even bother trying it.
That size is correct, however.
The only company (that I know of) that makes a low w/f belt of that size is Marrs.
I use a Teac belt with a different length (a very low w/f belt) and re-located the motor so that the tension is correct.

 

[GOYA]

I'm seeing none of the problems described in the reel motor thread.
The problem with the PRB belt sounds like my situation. Thank you for finding that, Hajidub.
Marrs communication is no longer in business. I may try a belt from turntableneedles.com.

 

[GOYA]

I put the old belt back in and although it has its own problems, the flutter I heard with the new belt is not one of them. I am trying a PRM FRSP6.5 per suggestions at Tapeheads.net. The FRSP is supposed to be a much better belt for this deck.

 

[GOYA]

Just to tie up a loose end, here's how this came out: I got the FRSP belt on but it didn't help much. I ordered some belts for another deck I have, an Akai HX-R44, and I noticed that it has a motor that can be used to replace the one on the Nak deck. When the Akai belts arrived I also did a motor swap. The Nak now sounds very good. The Akai doesn't have W/F problems but the unsteady speed of the Chinese motor is still a problem there. I also found that the tape I had been using to test the Nak was missing its felt pressure pad. Anyway, I now have a Nak deck that performs well.