Re: IIgs Monitor Repair

[grent@comcast.net]

On Jan 8, 6:05 am, "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.
>
> >> I switched off and unplugged the monitor overnight and retested this
> >> morning. After a brief warm up period (say 30 seconds) the image
> >> became visable with good contrast and focus.
>
> > This sounds like a case of what would be called "pot noise" if it
> > were an audio application.  When a pot is seldom changed, the sliding
> > contact with the carbon element can become dirty/imperfect, and, in
> > some cases, temperature- or stress-sensitive.
>
> > In most of these cases, simply turning the pot several times back and
> > forth over the normal set point will clean the contact and element and
> > restore normal function.  In extreme cases, use of a specialized cleaner
> > is called for.
>
> > I'm glad that you got it working!
>
> >> I will do some more testing tonight to determine if this has fully
> >> fixed the problem. I have only been running the monitor with the
> >> textual IIgs startup screen (the one with the Apple flying backwards
> >> and forwards) as I removed all of my prized expansion cards from the
> >> IIgs before testing. When I fire up GS/OS it will give a better
> >> indication of the clarity due to the higher resolution, but from what
> >> I'm seeing, I'm pretty confident it will be OK.
>
> >> Now if only I had the knowledge to have tried this sooner, I could
> >> have avoided inhaling all of the solder fumes (yes I am aware they are
> >> not good for you and I do avoid them as much as possible!). You live
> >> and you learn.
>
> > They can't be too bad for you--I've breathed them (just incidentally)
> > for years and I'm not dead yet.  ;-)
>
> > Seriously, lead vapor is a potential issue, but the vapor pressure
> > of lead is quite low at the melting point of solder.  A fume hood
> > is not justified.
>
> >> So it would seem that the components in my monitor are not faulty,
> >> just the technician.  ;-)
>
> > ;-)  Many times I have made the same observation about myself!  ;-)
>
> >> I'll post back tonight when I get around to doing further testing...
>
> >> Thanks guys, my daughter will be pleased to get her computer
> >> operational again.
>
> > Good for you, for sticking with it and being willing to experiment.
>
> OK, my daughter has been playing on her IIgs for about an hour now. The
> monitor still does have a problem, but it is much easier to live with
> now. It still does get gradually brighter, but due to the adjustments I
> made last night, you can get a reasonable picture by just adjusting the
> side controls (i.e. you don't need to open the case). It has only lost a
> little focus and is still readable at this stage.
>
> 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?
>
> Thanks,
> Mike
> --- Synchronet 3.14a-Win32 NewsLink 1.85
> A2Central.com - Your total source for Apple II computing.

 Hi,
  The fumes might have been mostly rosin, not that is good for you or
any better.
I would have tried to cool down compents before I replaced them. That
is I would run the monitor for hours to heat it up for the problem to
come up. Then shut it down then spray a component with one of the
cooling agents. Just enough to bring it down. Not enough to cause
frost, if there is enough moisture in the air.

Then I might have tried replacing whole boards if I was not sure,
rather the components. Which takes a longer time.  Once a board
replacement fixes the problem. Then component replacement would start.

Take Care