Re: Commodore 1084S monitor

> --Alex W. Jackson--

> > Hi Alex! Did you ever solve this? Having exactly the same issue > with exactly the same monitor. Thank you in advance!

Did you honestly think that replying to an 18 year old posting was likely to get you anything more than insults?

Idiot.

Reply to
Google Groups Idiots Strike Again
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It's been over 17 years since the original message was posted, so it's unlikely that anyone remembers the result even if it did get fixed.

What have you tried so far to fix or narrow down the problem, if anything?

It sounds like some kind of ghosting or ringing; is there a picture you could upload anywhere (Imgur or similar) so we can see what it looks like?

I'd start by swapping the video cable and also trying a different video source, just to make sure it really is the monitor at fault. Then I'd replace all electrolytic capacitors on general principle. These monitors are decades old and there are probably multiple caps that have gone out of spec by now, so just doing the whole lot can save multiple rounds of troubleshooting.

There's a service manual for this monitor available at

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The scan quality is poor, but it's certainly better than nothing.

Rayner

--
Big-8 Management Board: https://www.big-8.org 
Homepage: http://magic-cookie.co.uk
Reply to
Rayner Lucas

Hi Rayner,

Firstly just wanna say to the Google Groups Einstein that the 18 year period doesn't matter as long as the problem was solved and the guy is still around on this earth. The Commode/Amiga retro-scene is very much alive.

Now I have posted lots of pics and info in this thread. I have already recapped the monitor and done a lot of measurements.

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I thought I'd also ask here as Alex faced the exact same problem.

Thanks for your time Rayner.

Reply to
George Alibinisis

You do need to know that the position of Village Idiot is occupied by an Australian at this time. Much as you might wish to compete, your status will remain "incurably stupid", only. You may re-apply should the incumbent leave.

Reply to
Peter W.

Get a life Peter instead of running stupidity contests in Google groups especially when you are the undisputed heavy weight champion. No way for the rest of us to win.

Reply to
George Alibinisis

George:

Then you are in full competition with Phil for the position? He may be relieved to know that.

Reply to
Peter W.

you re not funny dude

Reply to
George Alibinisis

vertical-lines.396322/

It's odd to see such an old thread get resurrected, but it is still a relevant post even if the original participants are no longer reading, so in this case I don't think it's anything to get worked up about.

I see from that edaboard thread that you've already tried the most likely solutions :-(

The slowly drifting *horizontal* lines you mention sound like hum bars, i.e. excessive voltage ripple from the power supply making its way onto the display. If this is the case you'd see two bars on screen at once (100Hz ripple from a full-wave rectifier, on a screen with 50Hz vertical refresh) Again, by far the most common cause is a bad filter capacitor in the low-voltage power supply, but there can be other components at fault. See

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If you have access to an oscilloscope, you might want to check the outputs of the power supply for unusually high ripple. In particular, the output of the 12V DC regulator (IC403) ought to look nice and stable, as the regulator should smooth out whatever makes it past the filter capacitor.

Obligatory safety note: be very careful and don't work alone, these things have some nasty voltages inside them (including that 125V DC power supply output). I highly recommend the safety guidelines at

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Rayner

--
Big-8 Management Board: https://www.big-8.org 
Homepage: http://magic-cookie.co.uk
Reply to
Rayner Lucas

thanks for all your efforts Rayner. I am using a 1:1 isolation transformer when I power up the monitor and I do have an oscope. Ill test the PSU altho ugh the lines are many more than two.. maybe 7-8 drifting to the bottom of the screen. Thing is that there are brand new caps everywhere.

I read around the internet and there was this thread and just one more guy with same monitor, same issue. He told me on eab boards via private message that his monitor is with an expert at the moment.

it definetely looks like some harmonic but my knowledge in CRTs is very lit tle at the moment - learning every day.

Reply to
George Alibinisis

Okay, if there are 7-8 lines it's not mains frequency. I'd say it's still worth checking the PSU output voltages for stability, though - it will help to know whether you can rule that section out or not.

The number of horizontal lines suggests the unwanted oscillation has a

350 - 400Hz component, which might be a helpful clue.

If investigating the PSU doesn't reveal anything, here's how I'd look at it. You've got a scope and a schematic annotated with expected voltages and waveforms. The problem shows up on the display, therefore it must be present among the signals and voltages that go to the CRT and deflection yoke. If you can figure out which one(s), you can then trace it back to the origin from there.

It seems highly unlikely to be anything to do with the EHT or the focus grid voltage, which is good because those are the ones I'd least like to be messing with.

It doesn't look much like a deflection problem either, as from the pictures on the edaboard thread I can't see any actual distortion to the image on screen.

As far as I can see, that mostly just leaves the:

+12V line +125V line

-20V line RGB signal lines

going to the CRT neck board as the likely candidates.

The safety guidelines at

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include some advice for staying safe when investigating a running monitor; I particularly recommend the bit about only ever connecting/disconnecting test leads when the monitor is unpowered and unplugged.

Let us know if you manage to narrow it down.

Rayner

--
Big-8 Management Board: https://www.big-8.org 
Homepage: http://magic-cookie.co.uk
Reply to
Rayner Lucas

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