I read the comment of Oct. 7 in the '729 e-mail log' about the Master Skew tape not being a 'field' item and thought you should be aware that Master Skew Tapes were indeed a 'field' item. As I recall most tape accounts had one on site or the FE with multiple accounts had one. FYI: No real magic to it. The Master Skew Tape was simply created with a tape head that had just one write gap all the way across the tape.

Tape heads wear and both read skew and write skew change as they wear. Tape heads also wear out. CE's replaced worn out or failed tape head assemblies. That necessitated adjusting both read and write skew and that required having a Master Skew Tape.

To the best of my knowledge, my company was the only one in the US that had the expertise and equipment to rebuild and test 729 and 2401 tape heads of all models. We delivered them as a complete, tested and guarnteed 'Clamshell' assembly and rebuilt hundreds of them for many different companies. NASA and FAA are two that you would recognize.

I agree with your, and Bob's, recommendation to not adjust anything in the R/W electronics until the tape drive is mechanically functional and then only when absolutely required to make it operational. Anything beyond that should be undertaken only by someone who knows exactly what they are doing and why.

In very simple terms read and write skew is adjusted as follows to produce as close as possible, zero skew on the tape and on the read bus: While reading the Master Skew Tape read skew for each track is adjusted to provide as close to zero skew as possible on the read bus for all tracks. Then a scratch tape is mounted and while writing all ones, write skew is adjusted to duplicate, as close as possible, the results seen on the read bus as in the step above.

John Falk

Did you mention that the guys at Santa Clara restoring the RAMAC worked with a machinist at IBM San Jose, where he machined the capstan part from a rubber head mallet (hammer)?

- Robert

1. Trying to find someone at Burke Rubber, the original manufacturer and still doing business in San Jose, who (1) remembered what the material was, and (2) would be interested in trying to make us a new one.
2. But the better idea came from a discussion between Jack Grogan, now retired, and Lynn Liebschutz, now of Hitachi. This is the scenario that follows:
   • Somehow it was determined that the correct durometer rubber for this application is nearly the same as that found in a rubber-headed mallet as found in an auto tire shop. Such a mallet was procured and a core was taken from it. The rubber "tire" was removed from the old pinion and the rubber core was machined inside to match the metal core and the new rubber was bonded on. Then the new "tire" was machined to the dimensions of the original. It works perfectly.
   • The work was done by an Hitach model maker under Lynn's direction. Lynn would be the key to duplicating the process if it seems appropriate. I don't have access to Hitachi phone numbers, but his e-mail is probably lynn.liebschutz@hgst.com.

We are missing a couple of the complete 'STOP' capstans. We also have some that have lost their outer rubber surfaces. Steve is looking into machining new stop capstans but we have not come up with any spec's for the rubber compound. Does any one have any thoughts as to either where we can find some of the engineering spec's for the rubber parts or have any thoughts on the composition & methods to attach it to the steel roller.

Master skew tapes & Unicorn horns. I do believe that is one item we will never find. They were not really a 'field' items since the CE's never really did anything to change setting or replace those parts that would require a 'master tape'. I used one while in the Poughkeepsie plant working in the 727/729 final test department. I agree that we make no changes to any read/write settings until we have actually run tape through the machine & can view the different levels with a scope. I recommend that we work backwards when doing this. Starting with the read out puts & working our way back in through the write/read sequence.

As to the actual loading/unloading & forward/backward transport of tape, that should be very easy to correct. You use two strips of tape that you move up & down in the columns by hand.

I do not plan to remove any capstans motors unless we have a defective one. We will try to go with the rubber rollers 'as is'.

I look to turn on 'power' & start the mechanical testing in about three weeks. We are replacing the clutch belts, checking vacuum switches, working on power supplies and cleaning up the insides. Once we start the 'rebuild/reinstall' it will go fast. My plan is to bring up the 2 Mod V's together & get them on line. Then we turn to the 2 Mod II's

Again I agree that we should not touch any 'delay line', 'preamp' 'skew' setting until we have taken all the current reading & then see if & what needs adjusting.

Allen J Palmer