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Author Topic: Strange display problem - recap needed? (Read 637 times)

Offline John Fante

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Strange display problem - recap needed?
« on: 2020.July.06. 11:33:19 »
I am having a strange display problem.

I have connected my EP128 to a OSSC. I use the same for all my other RGB retro machine (MSX, Spectrum, Amiga) and it works flawlessly. No issues what so ever!

However I have a strange display issue with my EP that is beginning to bother me. I am almost sure it is hardware related and I am beginning to thing that my EP needs a recap or something since the problem shows itself after a 3-5 min.

When I start the picture is fine and the letters are clear. See example here.

However, when the machine has been on for 3-5 minutes I get this strange artifact where the letters are dithering. I have not seen the issues with games etc. I have tried changing the scart cable and changing the settings on the OSSC but with no succes - at least so far.

Any suggestions? Things I can check to see if it is hardware related?

And is it normal to have to recap an EP?
 
PS: Just to absolutely clear :): I bought the machine from ZoZo and I have been very pleased so far. It is not in any way an error I am blaming him for!

Online gflorez

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Re: Strange display problem - recap needed?
« Reply #1 on: 2020.July.06. 14:24:39 »
These artefacts happen when the final horizontal resolution on the monitor is not the same that the one on its input connector.

You can search the proper resolution with the horizontal width manual control.

I have a multi scan monitor that needs it.

Not a big problem. On the right setting you will see all the vertical bars on the letters all the same width. Observe the strange  "M".

Edit: Only the very first EP64 with Philips capacitors need to be recapped.
« Last Edit: 2020.July.06. 14:27:48 by gflorez »

Offline Zozosoft

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Re: Strange display problem - recap needed?
« Reply #2 on: 2020.July.06. 15:01:57 »
Can you test it on a real CRT Scart monitor?

If it is also presented then I think about small inaccuracy in Nick clock.
Try to recap not a bad idea after a 35 years :-)
Also a good idea try a brand new replacement PSU. Someone in the Hungarian forum wrote it, get a more stable screen after bought a new PSU. Probably also good idea replace the internal power circuits with a EPower, but I'm afraid it is sold out :-(

One another idea: check the Nick heatshink. The old glue start loosening after 25+ years, in a many machine the heatshink completly fall down.

Online gflorez

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Re: Strange display problem - recap needed?
« Reply #3 on: 2020.July.06. 15:52:48 »
Ok, but first try to adjust manually the horizontal control. It is easy.

Really, I have exactly the same issue like on John Fante's video on my monitor when I let itself to adjust video automatically.
« Last Edit: 2020.July.06. 16:43:24 by gflorez »

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Re: Strange display problem - recap needed?
« Reply #4 on: 2020.July.06. 16:12:48 »
See some examples on my monitor:

Un-adjusted, observe the thickness difference on the vertical pixels on the "o" and the "M".:

25036-0

Adjusted:

25038-1
« Last Edit: 2020.July.06. 16:26:24 by gflorez »

Online gflorez

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Re: Strange display problem - recap needed?
« Reply #5 on: 2020.July.06. 16:14:42 »
Some videos can also aid to show a better example.

This one is un-adjusted.
« Last Edit: 2020.July.06. 16:24:10 by gflorez »

Online gflorez

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Re: Strange display problem - recap needed?
« Reply #6 on: 2020.July.06. 16:20:18 »
This is when manually adjusted. Sorry for the bad focus. The characters are solid.
« Last Edit: 2020.July.06. 16:25:18 by gflorez »

Offline John Fante

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Re: Strange display problem - recap needed?
« Reply #7 on: 2020.July.06. 22:00:37 »
Thank you for all the good advice! :)

I will try them one by one and see what does the trick.

I will report back :cool:

Offline John Fante

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Re: Strange display problem - recap needed?
« Reply #8 on: 2020.July.07. 17:46:35 »
These artefacts happen when the final horizontal resolution on the monitor is not the same that the one on its input connector.

You can search the proper resolution with the horizontal width manual control.

@gflorez: I am a bit unsure what you mean by this :) the OSSC I use have A LOT of different settings and should compensate for changing resolutions.

Btw: It is not the heatsink. I opened the machine and everything looks fine. The heatsink is still firmly connected to Nick :)

Tomorrow I am getting a polarity changer for so I can use this power supply directly and not have to run it through Pear's floppy controller. Just to rule that out also.

Online gflorez

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Re: Strange display problem - recap needed?
« Reply #9 on: 2020.July.07. 19:06:37 »
What I mean: The video signal is correct when coming from the OSSC. Is the monitor(the very last stage) who produces the artefacts, because the program that governs the monitor synchronism thinks that the input signal is not "standard". Then it adds some vertical lines(LCDs have vertical lines) to make the video information fit to the stored standard.

The artefacts are produced on these additional lines. When you configure the horizontal width of the monitor, what you are really doing is removing or adding vertical lines, so there is a place on the slider where you will find the correct horizontal resolution. The exact point is when the lines with artefacts are separating more and more. If the artefact lines are a lot and very near, you are far from the right point.

Please, try this easy monitor configuration before modifying the EP.

 


Offline John Fante

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Re: Strange display problem - recap needed?
« Reply #10 on: 2020.July.08. 12:31:14 »
So far I have not had any succes changing the settings in my monitor. Also shifting to another monitor did not change anything.

I am using a IIyama ProLite e2403WS connected to the OSSC. The manuel is here.

The OSSC outputs a digital signal and that does not leave much room for changing anything.

I think the problem is either related to the EP's output or the OSSC not being configured properly. And I think that most likely the problem is EP related since it comes after 3-5 min. of use. When I turn the EP on there is almost no display problem at all.

@ZoZo. You mentioned a "small inaccuracy in Nick clock.". Is that something that can be fixed?

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Re: Strange display problem - recap needed?
« Reply #11 on: 2020.July.08. 15:51:04 »
You have 2 controls to try on the monitor.


Offline John Fante

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Re: Strange display problem - recap needed?
« Reply #12 on: 2020.July.08. 16:45:19 »
Yes but that is only available with analog (dsub) input. The OSSC produces a digital signal that comes in through a DVi-cable.

I think you can correct the problem in your end because you have a monitor that uses an analog signal.

I have investigated a bit and it can be that the problem is caused by a sync problem. The csync line is maybe "jittering". Maybe the OSSC can correct this.

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Re: Strange display problem - recap needed?
« Reply #13 on: 2020.July.08. 20:59:41 »
Great! I hope that artefacts could be fixed with the external equipment.

Offline John Fante

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Re: Strange display problem - recap needed?
« Reply #14 on: 2020.July.09. 07:09:51 »
Thank you for all your good suggestions. Your effort for the community is huge :D