Restoring a HP9830B calculator.

[MattisLind]

What happens when pressing the REWIND key:

That depends. If is reasonably near end of tape (up to maybe one third into tape) it will rewind to clear leader without me holding down the button. So EOT/BOT detect works. But it happens when further into the tape that I need to keep it pressed or when I press it moves maybe 10 seconds then stops. It sure looks like some kind of mechanical problem. When it stopped like this, before it reached BOT, and then I just ejected and reinserted the cassette it would turn another 10 seconds when pressing the REWIND button. Without this manoeuvre it would stop immediately.

Yes it runs when executing the MARK command. And it runs for almost the entire length of the tape which was not what I anticipated. Then suddenly it stops and the machine is hung. Pressing STOP doesn't help. This could be a missing write clock. I'll check that.

Is there some circuitry which stop movement if the torque needed is to high?

I will test with other cassettes but this type of data cassette with blank leader is quite tricky to get hold of. I am not sure that the leader of a standard audio cassette would be detected. A few old cassettes had a problem in the DEC TU60 where the friction against the head and felt pad was to high. Apparently this is a common problem that the oil on the tape evaporates over the years which then would increase friction.

The issue that a eject / insert cycle makes a difference is puzzling to me. I simply cannot understand what kind of difference that makes.

So: Yes. There could be a mechanical problem in the drive. Or the torque applied by the motors is to low. Or the cassette is not very good (although these works in a TU60). But the BOT/EOT detector is ok.

It has to be some kind of fundamental problem that gives an immediate ERROR 58 to all other tape operations. So I think that there are some logical problem as well. I'll check those small micro switches to see if those are all right.