Re: HP 9821 - display and tape transport issues #VintageHPComputers


9821A finally opened

Here you can see photos of all the boards.
Some of them are not the best quality (sorry).

So far I've repaired the lever for paper feed.

Next thing to do is a tape transport.
O-rings looks OK without any dents, cassette pulling strength and speed seems to be OK as well.

But it not behaves properly....

1) Rewinding.:
- when I execute "<>REW" command, it is rewindig but only for about one second and then stop immediately.
Here you can see video (few times executed <>REW command on execute keypress).

2) Program load "<> LDF 0".:
- after few tape turns when clear leader is finished it starts to behave strangely.
electromagnets on the both sides flip back and forward, then tape finally is rewinded back to begginnig.
This test was made on origin HP cassete which is OK in 99%.

3) Mark command:
- when I run "<>MARK 1, 5"; command it's running and running....don't stop.

Do you have any idea what shall I check first ?

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