9815/9825 Capstan

[aj04062]

Can someone point me in the direction of a good repair method for these capstans?

thanks
Adam

[Craig Bladow]

I'm interested also. I have tried the "Silicone Tape" repair but it survived for 1 mark operation and rolled off the capstan on rewind. I have 10 mm heat shrink tubing on order for the next attempt. If you search for HP-85 capstan repairs there is a fair amount of information. If you search this site for '9815 capstan' you should find the thread that I am documenting my lack of progress!

[Geoff Quickfall]

Tygon turrned on a lathe to the correct outer and inner diameter. Kluging doesn't seem to work.

[Craig Bladow]

My 9815 capstan is 3/8" (0.375 inch), cruff in another thread stated that the outer diameter is nominally 0.425 inch. 3/8" inch inner diameter tygon tubing is commonly available, however the wall thickness is too much. I'm curious as to how one goes about mounting tubing on a lathe (or drill press) so the outer diameter can be reduced.

[Paul Berger (Canada)]

(06-06-2017 03:02 AM)Craig Bladow Wrote:  I'm interested also. I have tried the "Silicone Tape" repair but it survived for 1 mark operation and rolled off the capstan on rewind. I have 10 mm heat shrink tubing on order for the next attempt. If you search for HP-85 capstan repairs there is a fair amount of information. If you search this site for '9815 capstan' you should find the thread that I am documenting my lack of progress!

I replaced the tire on the capstan of a HP-85 using heat shrink what I did was spin the motor while heating the heat shrink in hopes of it shrinking evenly all the way around, and it worked.

Paul.

[cruff]

(06-07-2017 06:54 PM)Craig Bladow Wrote:  I'm curious as to how one goes about mounting tubing on a lathe (or drill press) so the outer diameter can be reduced.

You can use the tape drive motor itself as the lathe, just power it with a suitable voltage and current. I found about 10 V and enough current to prevent the stall worked for mine. Ideally you would remove the motor from the drive to prevent material removed from the new rotor from mucking something up, but if you are careful, you can probably shield the rest of the drive from the debris.

[Craig Bladow]

Another repair technique uses superglue and thin vinyl tubing used for coating tools: http://www.hp9845.net/9845/tutorials/tapedrives/

I have not tried it, still pursuing the heatshrink solution.

[Katie Wasserman]

From long ago....

[Etienne Victoria]

FWIW I used to rebuild the capstan this way. and mount it back this way.

In my poor english descriptions, replace "tap joints" by "washers".

I repaired a couple of 9815s and one 9825 this way a couple of years ago...

Etienne

Edited for typos.

[Paul Berger (Canada)]

I just rebuilt the capstan on a 9825T drive and did the DC-1000 conversion at the same time. I did not machine off the old wheel but rather I added about 2.5 mm of height using a piece of hard plastic glued on top using cyanoacrylate glue. Since I don't have a lathe available to me I ground the plastic down to the same size as the metal wheel using emery boards and a file with the motor running off a DC supply. Once I had it down to size I slipped on and glued a piece if silicon tubing but the outside diameter was too big so ground it down using emery boards with the motor running. None of the DC-100 cartridges I have are any good even the new-old 3M ones I got the media keeps sticking to the drive band and getting wound up in the cartridge, however I recently got some QD2120 tapes, these are a 120MB version of QIC-80 tapes and after thoroughly erasing them with a bulk eraser I was able to mark files on the tape, store a program and read the program back from the tape. I have not tested this extensively yet but it looks promising. Now I will need to do the drives in my 9835A and my other 9825T, but first I think I will look into getting a small lathe. I got this one working without a lathe but I see now that a lathe would make it a lot easier.

Edit I forgot to mention one problem I had with the QD2120 tape is it positioned the tape between the single start of data hole and first pair of double BOT holes and when it would try to find the start of tape it would fail with an "unexpected BOT" error, I had to manually move the tape forward part the start of data mark and then it was OK.

[Craig Bladow]

I have a working tape drive in my 9815 now! I removed the motor, slipped a length of 10 mm heat-shrink on the capstan, used a variable voltage power supply to turn the motor while applying heat from below the capstan. The first NOS tape I tried ended up with a failed drive belt. The second one worked! Note that I always manually spool the tape to find the single hole and place it on the spool with the least tape to make sure the drive belts aren't stuck to the tape.

The journey to a working tape drive included replacing a transistor in the EOT circuit, replacing the EOT lamp, which was working in the beginning, after spooling off two carts and multiple capstan repair attempts including various tubing types and silicone tape.

[aj04062]

Nice! Did you use tubing with the glue on the inside? Was the material Polyolefin?

(08-26-2017 06:18 PM)Craig Bladow Wrote:  I have a working tape drive in my 9815 now! I removed the motor, slipped a length of 10 mm heat-shrink on the capstan, used a variable voltage power supply to turn the motor while applying heat from below the capstan. The first NOS tape I tried ended up with a failed drive belt. The second one worked! Note that I always manually spool the tape to find the single hole and place it on the spool with the least tape to make sure the drive belts aren't stuck to the tape.

The journey to a working tape drive included replacing a transistor in the EOT circuit, replacing the EOT lamp, which was working in the beginning, after spooling off two carts and multiple capstan repair attempts including various tubing types and silicone tape.

[Craig Bladow]

(08-27-2017 12:37 AM)aj04062 Wrote:  Nice! Did you use tubing with the glue on the inside? Was the material Polyolefin?

No glue, the heat shrink tubing material was Polyolefin, the tubing was flat, which held it on to the capstan so no glue was required.

[vassilisprevelakis]

Let me just say for the record that Katie's suggestion really works. I have used it on practically all my Series 80 computers, my 9825 (thanks Katie :-) and some 9815 machines that I fixed for a friend.

They all work fine after quite a few years.

Also, having tried both heat shrink tubing and the tape, I can say that the tape fix results in quieter operation and practically no tape stalls.

**vp

[Craig Bladow]

Could you post the details of the tape solution that works for you, as that would help me and others. Is the capstan removed from the motor? Width and length of tape, how many layers of tape? Final diameter? How much, if any, of the overlap is trimmed off?

[vassilisprevelakis]

Many years ago I made this page:

http://www.series80.org/Articles/capstan-repair.html

with info on the capstan repair for the HP-85. The same fix applies to the 9815, 9825, 9845 etc machines since they have the same (mechanical) design for the capstan.

Also have a picture of a capstan with whats left of the original capstan coating and I use that to calculate the approximate thickness.

When you insert the tape, there is some play, so the dimensions need not be exact.

**vp

[vassilisprevelakis]

(09-09-2017 08:25 PM)Craig Bladow Wrote:  Is the capstan removed from the motor? Width and length of tape, how many layers of tape? Final diameter? How much, if any, of the overlap is trimmed off?

I have never needed to remove the capstan from the motor.

I did have to remove the motor itself and unsoldered the two tiny wires from the tacho sensor

I vaguely recall that you have to be sure not to cross them when you reassemble the motor, I could be wrong though, since its been some time since I repaired a capstan.

Having said that I have repaired about ten tape drives with the tape method and they are all working OK even after 8+ years

The overlap is important ! You have to smooth it out. Its very easy you wait 8-10 hours for the tape to firm up and then you run the motor (anything between 9V and 12V should be OK) holding a file against the wheel. Worst thing that can happen is that you file the tape away and you have to do it all over again.

After reassembling, you can test your repair by retentioning a scratch tape (the command on the HP-85 is called CTAPE). If it works you know the capstan can move the tape without slipping.

**vp

[Craig Bladow]

Thank you for the detailed instructions. Apparently I did not leave the newly applied tape on long enough.