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My hp85's cassette tape has a bad gummy wheel.

Any suggestions on what to use for a replacement?

Thanks,

Andy

I used some shrink tubing with success.
I'm not certain that's the best solution, but it worked for me.

I also used heat shrink tubing on a 9825 tape drive - same cartridge but maybe not the same mechanism. Made the tape move OK but have other problems on that machine. On the 9825 there is a delicate-looking optical tachometer wheel close to the rubber wheel, on the same shaft. I shielded the rest of the mechanism with aluminum foil while I heated the tubing.

Actually, Ellis brings up two good points:

* Do shield the mechanism from the heat! Mine started to melt slightly, because my shield was not so good at first and I had to be VERY careful!

* The HP85 has an optical sensor also, and it appears to have some special calibration that has to be performed with an oscilloscope to look for a particular waveform. I don't have that calibration manual, but I think I recall someone else mentioned it earlier, and I may have a copy of a part of those instructions that I can look for, if you get to a point where you've replaced the wheel and still have problems...

Thanks...

I actually have the original HP85 Assembly Level Service Manual and it has complete instructions for performing that calibration with a scope. So if you need it, let me know.

Andy

Ellis I noticed you said you have other problems with your 9825 - Tape drive ? if I could be curious what problems are you having ? I have been trying to fix my 9825 Tape drive and despite finding and fixing a couple of problems still seem to have more somewhere. Perhaps we could compare notes ?

Regards
Richard Freeman

I do have some interest in that particular section, Andy.
It doesn't have to be the entire chapter, but just that section.

What info I have is:

Mike,
According to the 85B, service manual (June 1983) the problem may be with the tape speed circuit alignment.
LED DS1 on the capstan motor assembly and phototransistor CR1 on the tape transport assembly. This
would have been disturbed when you remove the capstan motor.
?Without a cartridge inserted, run the Tape Speed Test from the Service ROM. If the message {TAPE
STALLED} appears proceed with step k to reposition the phototransistor?
If you have an o?scope measure at tp-4 (upper tp lower left corner of tape pca) you will need to active the
drive if you do not have the service ROM (I do not have a copy) set the scope as followed:
10usec/div, 2 v/div, ac coupling --you should see 3 cycles of a sine wave the negative portion is limited. The
positive peak should be at least 2.5 v and the negative peak should be a least 2v. Reposition phototransistor
CR1 until the desired waveform is obtained.
If you don?t have a scope then I guess you can try it ?hit or miss?
Another interesting note ?if the customers computer can read tape cartridges that were reordered on the same
computer but cannot read cartridges recorded on another computer the tape head maybe out of alignment.
Align or replace tape drive assembly. Be sure to inform customer that the computer may no longer be able to
read tapes previously recorded on that computer?
Hope this helps
Regards,
JR


My problem is that I haven't attempted this, because I don't have Service ROM. Hence I'm VERY curious if your information gives me some clues as to how I might "fudge" or "klude" this step.

Thank you, Andy.

-Mike