9825/35/45 Tape Drive Info Request

[Ken Mowery]

I would like to design a solid state replacement (EEPROM) replacement for a HP tape drive like the ones used in the 9825/35/45 calculators. The actual machine of interest is an HP5420 Digital Signal Analyzer. It boots from a cartridge tape mechanically like the calculator tapes. The drive has been used so much it's shot. The rest of the machine is just parts without it. Does anyone know where to find a good design explanation of how this drives work so I could emulate its performance? Any leads would be helpful.

[Vassilis Prevelakis]

Although this is a very interesting idea you may want to consider an external HP-IB diskette drive. The 9121 is probably ideal for the task.

If, however, you are intent on going ahead, note that there is a guy who has developed the same thing for the DEC tape drives for the VAX. Although both the HP and DEC drives take the same media, I am not at all sure how similar they are in their external interface.

**vp

[Ken Mowery]

Interesting! I had a brief look around the net since your remarks. Can you give me any leads on how to find this guy or what key words to search for to find his work?

Do you know of a format name for these drives? What is a term to call them, besides HP calculator tape drive?? I know that the media looked very related, but not the same as, the much later "Colorado drive"

The 5420 automatically looks at the internal tape drive to load it's executable on powerup. It appears to have little or no hard stored program and is not smart enough to run the 488 bus until after it boots. Without the tape drive working, it's just a big (expensive) box of flashing lights. Believe me, there is nothing I would like more than plugging in something to fix this, but I'm afraid that it's going to be a bit harder. Even if I do figure out a H/W solution, I will need to figure out how to pull the data off the boot tape I have. I have already tried reading the tape with a 9825 and the data format is different.
Thanks, Ken

[Vassilis Prevelakis]

The tape drive is called a TU58 and was/is the boot device for the DEC VAX 750 mini and many other DEC minis. More information may be found at http://www.sparetimegizmos.com/Hardware/TU58_Emulator.htm. However the news are not particularly good as the TU58 appears to be rather intelligent (works as a serial device running a packet protocol) so it can be easily replaced with a modern microcontroller (the links refers to an 8051, but today a PIC will more than adequate).

I don't know what the HP tape drive looks like, but can't you replace the one in the 5420 with a tape drive from another machine (e.g. HP 85 - there seem to be lots of them around).

**vp

[Ken Mowery]

Outstanding Lead !!! Thanks I'll be attempting to monitor the data traffic to and from the drive with RS422 in mind and see if it makes any sense. This should allow me to image the data stream and play it back with several possible solutions.