campbell@gear.torque.net
Fri, 6 Mar 1998 18:21:51 +0000
> From: campbell@gear.torque.net
> To: Matti Koskinen <mjkoskin@sci.fi>
> Date: Fri, 6 Mar 1998 08:48:18 +0000
> Subject: [PARPORT] Re: ppa wants printer to be on
> Cc: linux-parport@torque.net
> > Date: Thu, 05 Mar 1998 10:18:55 +0200
> > From: Matti Koskinen <mjkoskin@sci.fi>
> > To: campbell@gear.torque.net
> > Subject: ppa wants printer to be on
>
> > hi
> > and thanks for the ppa-driver. I bought a zip-drive and got it work
> > with no problems, except one. Installation of ppa-module fails, if the
> > printer is off.
>
> *scratch head*
> This is the first I have heard about this one. I will shortly go fire
> up my trusty 486 (due for a mainboard/processor replacement) and try
> out this problem with my old HP DJ500.
>
> I wonder if anyone else has had this problem but not reported it.
Doubled checked my setup and it works fine with a printer plugged in
and turned off. The only explanation is that the laser printer has
very low resistance inputs.
I checked the input resistance using a DVM for my HP DJ500 and got
the following:
data lines 2.5k ohm
strobe line 1.1k ohm
init line 1.1k ohm
return signals ~500k ohm (almost open circuit)
The only thing I could suggest is one of those old printer switches
(the sort of thing you can pickup at a garage sale for a couple
of dollars).
The point about not connecting the cables while the machine is
running is to avoid "jolt" effects on operating circuitry when the
signal grounds come together (zero volts is only relative). The
switches get around the problem since the ground is always connected.
David Campbell
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