HP9826 Question - Basic 5.12 and such

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Apr 2 17:32:59 2004

> I have a question or 2 to ask on the HP9826. I am now the proud owner of

I don't have a 9826 (it's one of the few HP desktops I've not obtained
[1]) but the video circuitry is likely to be conventional.

[1] 2 off 9100B, 2 off 9810, 9830, 9815, 9825, 9831, 9845, 9836, 3 off
85, 3 off 86B, 87, 87XM, 9915, 150-II, IPC, etc...

> the labs old system.
> Now I have several issues to resolve. The first is the reason I have and
> the lab does not. The
> display is out of focus and not too bright. I have tried to adjust using
> the pots inside labeled focus
> brightness. It helped alittle but not much. Any ideas?

In general, problems are never solved by tweaking adjustments. The only
reason to twiddle presets is to see what, if any, effect they have on the
symptoms. If, for example, the focus pot had no effect at all, you might
start by suspecting the focus anode voltage was missing for some reason.

Anyway, dim and out of focus sounds like a CRT electrode voltage problem.
Alas you didn't measure the voltages when the machine was working
correctly (something I normally do do), so you've got nothing to compare
against. But I'd start looking around the line output stage (horizontal
output stage), possibly for a bad capacitor or a flyback transformer problem.

-tony
Received on Fri Apr 02 2004 - 17:32:59 BST