Re: IIgs Monitor Repair

[ferdimh@gmx.de]

On 8 Jan., 12:05, "Polymorph" <polymo...@a2central.com.remove-51g-
this> wrote:
>   To: Michael J. Mahon
>
>
>
> Michael J. Mahon wrote:
> > Polymorph wrote:
> >> On Jan 7, 1:24 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
> >>> It may still turn out not to be too hard to fix--just different from
> >>> what was expected.  ;-)
>
> >> Well, I'm glad I didn't give up so soon as I am rather happy and (a
> >> little embarassed to find that the solution was so easy) to say that
> >> the problem did appear to be the HV divider. After allowing the
> >> monitor to warm up (approx. 20 - 30 mins), I then adjusted the pots as
> >> Ferdinand described and was able to get a good picture (both focus and
> >> brightness). I left the monitor running for quite a while and it
> >> seemed to keep the brightness and focus settings.
>
Congratulations, you got it!
>
> It would seem if I wanted this monitor to be 100% I would need to spend
> more time on it - and I aim to do that when I can get a replacement
> monitor (I have a replacement monitor in my sights courtesy of eBay).
> But it seems fairly obvious the problem is in the HV/flyback transformer
> area.
>
> The problem does appear to be heat related, as it is now running with
> the case on, whereas last night it was running with the case off and
> probably heated slower because of this.
>
> If you were to keep investigating, how would you order, in likelihood of
> success, the following potential fixes:
> * replace electrolytic capacitors in the HV area?
> * replace non-electrolytic capacitors in the HV area?
> * replace resistors in the HV area?
> * something else?
>
Something else: It looks like you have found the problem so stick to
it. The problem is extremely likely to be with the focus/screen pots.
You should concentrate on this. There is only one cap which could
affect brightness, bot it would not affect focus and it would only be
able to REDUCE the brightness. The HV divider can usually not be
replaced, you'd have to replace the whole flyback assembly, which
can't be done at reasonable cost, if at all.
But there are other possible fixes:
 - turn the pots back and forth very rapidly (10 times or so) . After
that, turn the monitor on with SCREEN at minimum and readjust.
 - live with it (perhaps set up the focus with a warm monitor)
 - leave the case off (not a good idea for your daughter...)
 - install a cooling fan
 - drill two holes into the case to allow adjustment from the outside
 - attach an external divider.

Ferdinand