HP97 printer never turns off

[isanchez]

Dear friends,

I am trying to repair an HP97.
The thing is that when I turn it on, the printer head starts to move and never stops, even when I put the paper roll. It prints nothing, just tracks the head moves and pulls the paper.

I have tried with another (working) printer and still the same behaviour, so the problem is not in the printer itself.

The display shows nothing at all...

Do you have any idea about where can be the probelm?


Thanks and kind regards


Ignacio

[Hans Brueggemann]

you may want to inspect the ADV button. is it stuck?

[isanchez]

Thanks for your suggestion!!
Apparently it is fine, but I shall check it again.

Regards

Ignacio

[teenix]

(04-30-2018 08:01 AM)isanchez Wrote:  Dear friends,

I am trying to repair an HP97.
The thing is that when I turn it on, the printer head starts to move and never stops, even when I put the paper roll. It prints nothing, just tracks the head moves and pulls the paper.

I have tried with another (working) printer and still the same behaviour, so the problem is not in the printer itself.

The display shows nothing at all...

Do you have any idea about where can be the probelm?


Thanks and kind regards


Ignacio

Unfortunately, this could be any number of things. The paper adv is just a flag input to the ACT, which controls the PIK chip which in turn controls the print mechanism including the motor.

If the display is blank as well, the ACT chip or ROMs could be faulty. The 97 repair manual suggests replacing the main logic board as the first test, then the keyboard logic assembly, then down to component level tests, power up reset circuit etc. With the help of the manual, there are test points and waveforms that can be looked at with a CRO and multi-meter. There is obviously power and the motor drivers work, so I would guess it is further back into the main circuit.

cheers

Tony