Hi !!!

I'm fixing a mono JVC, wich I'll post when I get it finished.

I has two main facts.

The first was speed changes. I renevue all tires, betls and pinch roller. Also I changed the motor. But, with some tapes, it still has some problems around speed variations ...
Pinch roller takes the tape Ok, since the autostop works fine (the stop sensor is the one that goes inside the cassette betwen erase and playback heads). It stops working when pinch isn't ok. But it works perfectly now.
Motor looks quite stable, and I've clenaed and lubed all the mecha as well. . The speed variations aren't large, but still noticeable.

Of course, mecha adjust and test is performed using a crap BBX and a power supply to power the motor ... JVC design don't let you adjust the speed until you take the main board and mecha away !!!!. Courtesy of JVC

The second fact is a rare one ... I can't turn down the volume AT ALL, that is with volume at min position, the box sound like at half of volume !!!!. I found that the micmixing slider was completly broken ... Does it related to the faillure ?

Pedro

The capstan shaft might need a bit of oil.

Check the take-up torque, might be too high.
Sometimes the take-up friction pad is no good.

This is sort of a hidden problem that can
cause lots of damage to tapes getting jammmed.

Thank for the advice.
Please help me to understand, take-up torque is the one done by the "weel" that takes the tape from the capstan and put it inside the cassette. Is the FWD weel ?.
IF I understood, I changed the friction pad with a new one, adjusted the torke (this can be adjusted in three positions) in the following way:

Looking at taperecorders when new, the take-up force would be enough to move the tape, even without the pinch roller. That's if I press pause a little to lift pinch roller, tape most run (at some speed). All new tape recorders I saw do the same, so I tried to adjust torque to match this behavior.
Pad is new, because the old one was to hard, and didn't worked. The speed compensation betwen the capstan and the FWD weel was made at the tire !!!!. Of course this shortens the tire life ...
That you say about the shaft happened with one of my Panasonic. Really you are rigth, the problem was complex. But I noticed the following
When the problem is in the pinch, the speed changes and always result in lower speed.
With this Pana was a rare one. Speed lowered a bit and then recovered alone, then went slow and then normal without touching nothing. Looked like a motor issue, but some extrange noise come from the shaft. The bearing was bad. No way Man. The only solution was to lube the shaft and put a bit smaller belt to avoid flyweel resonation (this produced noise and lowered speed). Then I turn up the motor a little. It worked Ok.

Finally in this JVC, I lubed the shaft. The pinch is new and the pad also. The shaft runs very very smoth, and motor is Ok. I think that the problem is the head (perhaps it's surface isn't as smoth as when new and friction with some tapes take too much force)
I keep it playing to see if I can figure the problem. Only some tapes shows problems. Other plays ok (perhaps a very little faster than I have adjusted).

We wait .... and we wonder =)

Thank for your advice !!!

If the problem is from some tapes.
Some tapes get tight in the spools
by tape moving up and down.

FF than REW the tape to smooth the tape.
You probably already know this.

Another odd problem is the tape head going in too far into the tape causing too much pressure on the tape-head-pad in the cassette.
There might be an adjustment for this.

The cassette case positioning posts might not be proper too.

Yes I know that, but I think that is a such common problem with tape users, so tapedeck design MOST work ok, even with that problem.
Actually you are rigth. I noticed that doing a little force with a finger in the RWD weel while playing lowers the speed. But I saw some tapedeck that this little force hadn't change the speed. I think a good design most hide this problem to the user =). Of course motor should keep the RPM constant across torque fluctuations
(inside a logical range). I'll try to move the tape as you say ...

I'll post some pictures soon. It's a great sounding with a warm sound and quite well made.
Here a saw some brochure an appears like the RC525, but mine is another model (I don't remeber now). Look the same.
Good JVC product. But at the same quality level ... I would prefeer a Panasonic

Pedro