Tape Drive Repair

If you have worked with these drives you will know that rubber surface on the capstan drive wheel turns to goo over time. So, no matter the condition of the equipment you must assume that the capstan will need repairing.

For those of you without experience in this area, please follow this advice, whatever you do DON'T put a tape into a drive that hasn't been repaired as you WILL get a mashed tape!

Below is an example of a tape drive in need of repair.

Repair of the tape drives has been covered quite well on other websites as there are number of systems that use the tape drive suitable for the DC-100A tape cartridge. Two sites I have found useful are www.hp9845.net/9845/tutorials/tapedrives/ and www.ideawindow.com/hp-85.html The second of these sites had the best of the cheap solutions. This and the other techniques worked well with the HP85 which I used to gain experience working on this kind of tape drive. However, the HP85 handles the tape more gently than do the 5420A and 5423A systems. The read/write speed of the HP85 is 10ips (inches per second) whereas the 5420/23 perform reads and writes at a speed of 22ips and has a winding speed of 88ips. So with some cheap solution is doesn't take long before the new surface starts to slip off if it's not glued or if the surface isn't smooth to start with over time you will get some damage to the tapes.

Much of my initial testing was done with tapes that were already fragile but didn't have any useful content so they could be cycled in the 5420 drives then read/write testing was performed in the HP85. You may be wondering how I used tape drive in the 5420 to cycle the tapes, as part of this project I have been disassembling code so that I could learn how parts of the system work and write new code to perform tests and ultimately capture the system software so it can be saved on better memory than tape.

After trialing some of the capstan fixes for the HP85 I came to the conclusion that as control tapes are rare and as the likelyhood of finding a control tape with no bit errors at all will be harder to find I didn't want to risk any tape with a capstan repair that could catastrophically damage a tape. My initial thought was to have a new piece of rubber vulcanised on to the wheel, then I found the Ebay seller "rfhk" who sells rubber sleves for the capstan. This sleve also has rubber in the top and bottom of the wheel so that the sleve is more like a tyre and it remains captive on the wheel. You may think that US$30 is expensive but I've found them simple to install and so far they have been 100% reliable as compared with the other fixes I've tried.

Here is an example of the sleve / tyre