Sony KA1ES help - tape skewing?

[shimniok]

I have this KA1ES deck that is skewing the cassette tape at the pinch roller / capstan towards the outside edge. In other words, when playing a tape, the tape isn't centered on the cassette's takeup reel. Or put another way, the tape isn't in the center of the pinch roller.

The deck has brand new, factory set of belts and pinch roller / assembly.

The new rubber helped a little but didn't completely eliminate the tape skew.

EDIT:

I've tried playing with motor torque which didn't cure it. Inspecting the tape path shows no curl at the tape guides. I played a little with pinch roller alignment to no avail. See update posted below: http://www.audiokarma.org/forums/showpost.php?p=3200267&postcount=8

Any other ideas?

Thanks,
Michael

 

[cbrworm]

Could the rubber pinch roller be mounted askew? Maybe the spring pressure is not holding uniform pressure against the capstain?

Does it make a difference if you put more pressure on the pinch roller? I assume that if you pull the pinch roller back the tape realigns.

Does the capstain shaft have any lateral play?

 

[shimniok]

Thanks for the ideas!

FF seems to wind the tape more centered than playing. Playing with the pinch roller pulled down seems to wind tape more centered, too.

Looks to me like the pinch roller is sitting true in its assembly. However, the pinch roller arm assembly mounts on a plastic shaft and there is a few degrees of lateral play. Forcing the pinch roller to move laterally definitely affects where the tape winds.

Also of note... the original pinch roller was totally shot and worn unevenly (maybe that is a clue). I was able to sand it fairly true and it performs about the same as the new factory roller, that is, it winds slightly off the center of the reel. So that tells me that the roller and its mounting in the assembly isn't an issue. But the mounting of the assembly on the shaft could be the cause.

I am thinking of shimming the pinch roller shaft to eliminate some of the play. And/or maybe replacing the plastic shaft with a metal one (non-magnetic, obviously).

Wished I had a mirror cassette so I could see more clearly what is going on in the tape path.

Michael

 

[koseltri]

You might try buying a pre-recorded cassette with a clear shell and cutting away the housing around the offending pinch roller, might let you see what's going on.

 

[Jon_Logan]

Yeah, you need a tape path inspection tape. Just get a screw together tape. Take it apart and chop out one side where it covers the tape path. Reassemble and you'll have a good tape traveling inpection tool.

Key factors are: Tape guide height. pinch roller parallelism. pinch roller pressure. pinch roller height. take up torque. back tension. A tape trveling tape will let you see how it skews. Using a screw driver to adjust pinch roller pressure might tell you if it is the cause. Usually, pinch roller assys have a way to adjust tension, via a different notch or hole for the spring.

 

[PacificStereo]

TOO MUCH TAKE-UP TORQUE. What you really need is a cassette torque tape. Torque will be regulated either via an adjustment, a clutch, or in some cases set by a reference voltage on the motor drive IC.

 

[shimniok]

Hm. Been looking for a cassette torque meter for a few weeks, no dice so far. Any specific sources for these?

Pretty sure torque is non-adjustable. The SM provides specs of what it should be... but it measures wrong, then what? Well, the manual doesn't say. Gee, thanks, Sony.

Michael

 

[shimniok]

Update:

1. Takeup Torque

The KA1ES has no torque adjustment. So as an experiment I threw a potentiometer in to adjust takeup motor voltage from 3.6V down to 2.5-3.0V ... any less than that and the takeup reel stalls. At any reduced torque the tape still skews somewhat.

2. Tape path inspection

I've cutout holes in a tape cassette to watch the tape path. There's no curling against the tape guides. It just seems to skew at the brand new pinch roller.

3. Pinch Roller

The pinch roller is brand new as are both belts. I tried playing with the alignment of the pinch roller... wasn't able to get much improvement. I guess I can keep playing with that and pinch roller tension. If I slightly reduce tension, the tape walks further outward. :scratch2:

The only other thing I could think of is to play with holdback tension but I'm not sure how to adjust or hack that.

:headscrat