Enterprise Forever
:UK => Hardware => Display => Topic started by: John Fante on 2020.July.06. 11:33:19
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I am having a strange display problem.
I have connected my EP128 to a OSSC (https://videogameperfection.com/products/open-source-scan-converter/). 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 (https://www.dropbox.com/s/aibxq885m2swof0/Picture_fine.mov?dl=0).
However, when the machine has been on for 3-5 minutes I get this strange artifact (https://www.dropbox.com/s/z9c4yfygwvmafq5/Picture_error.mov?dl=0) 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!
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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.
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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 (https://wiki.enterpriseforever.com/index.php?title=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.
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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.
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See some examples on my monitor:
Un-adjusted, observe the thickness difference on the vertical pixels on the "o" and the "M".:
[attach=1]
Adjusted:
[attach=2]
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Some videos can also aid to show a better example.
This one is un-adjusted.
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This is when manually adjusted. Sorry for the bad focus. The characters are solid.
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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:
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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 (http://junkerhq.net/xrgb/index.php?title=OSSC) 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 (https://www.digikey.dk/product-detail/en/mean-well-usa-inc/GST40A09-P1J/1866-2140-ND/) power supply directly and not have to run it through Pear's floppy controller. Just to rule that out also.
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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.
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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 (https://cdn.iiyama.com/f/8554959013f38b1b8b4bd9946e07ab0f_plb-e2403ws-8l-m021b01-en.pdf).
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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You have 2 controls to try on the monitor.
[attachimg=1]
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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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Great! I hope that artefacts could be fixed with the external equipment.
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Thank you for all your good suggestions. Your effort for the community is huge :D
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I found the solution to the problem.
In the OSSC settings you have to turn this on:
Allow upsample2x
Controls whether 2x samplerate is used instead of pixel repetition in certain modes, e.g. 384pX2, 480pX2, 480iX3, 480iX4, 960iX2.
On: 2x samplerate is used to double output horizontal resolution, which may be useful with sources that use off-spec horizontal rate. Alternatively, the option can be used to generate slightly more analog-esque (i.e. less pixellated) picture.
Off: Pixel repetition is used to double output horizontal resolution, which regenerates source image most faithfully if sampling matches dot clock. [default]
So as gflorez suggested it had something to with the horizontal resolution.
Unfortunately I messed up my keymembrame :oops: when I opened the machine to check the cooling on Nick. First some of the keys did not work and after a couple of tries to fix it now A LOT of the keys do not work. I am trying to find a new .... Until then I can not really use the machine :smt013
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First some of the keys did not work and after a couple of tries to fix it now A LOT of the keys do not work. I am trying to find a new ....
Usually need to cut few mm-s at the connection.
If not successfull: Then the Enterprise Club in Hungary made some membranes, write to Tutus (https://enterpriseforever.com/profile/?u=56) about it.
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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?
I thought about the jittering.
First look the internal 12V circuit. (http://enterprise.iko.hu/schematics/EP64-1~0.jpg)
Then the Nick clock circuit (http://enterprise.iko.hu/schematics/EP64-3~0.jpg), which is use the previously generated 12V.
This is why I guessing about power parts.
It is a well know problem, when something weak at power side, the two half screen start to make a sine dance on the screen.
With a L2 and C43 can adjusted the Nick clock, if the voltages are ok, then these can be used for stabilize the screen.
When the components warmed up, these two complex circuits are little change their frequencies. Especcialy the 12V circuit components near to the two 7805, which are generate lot of heat. And the 12V used by the Nick clock circuit...
On a some machine see the problem, screen start sine dance after few minutes, then used L2 for a fine adjustment, it is solved the problem.
Sometimes see machine if turned on below 20 celsius, start dancing screnn until few minutes warm up. Also fine adjustment solved it.
Another factor the Nick heat shink, especcialy at the 08-04 type Nick chips, which are more sensitive for a heat.
I thought about something similar happen at your machine, just in a minimal size dance, one pixel, or a less. Possible on a real CRT don't see anything, because it is very minimal. But at digital sampling can the minimal differences magnified. If one pixel started little earlier, then it is moved as one full pixel on the screen.
Nice, you find the right setting on the OSSC!
"which may be useful with sources that use off-spec horizontal rate."
IstvanV wrote about the Nick freq:
For the NICK chip, the clock frequency is derived from the PAL chroma sub-carrier (17734475 / 4 Hz), such that one line is exactly 284 cycles of that, which is slightly different from the PAL standard. Thus, the horizontal refresh rate is 17734475 / 4 / 284 = 15611.3336 Hz in theory, instead of the standard 15625 Hz. Although the circuit that generates the clock can be broken in some of the machines, resulting in an inaccurate frequency and "waving" picture or other artifacts.
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Great explanation, Zozo.
Sorry for being insistent with the external cause. The Enterprise video output was made analogic and for CRTs, and so, the images we actually see on our LCD monitors are always conversions. You Zozo, logically have sugested making tests with a CRT TV first, because it would show the real image before being converted.
On the near future it will be harder and harder to connect the Enterprise on the TVs that will come. I think that this same problem or similar will arise more frequently.
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@ZoZo: Thank you very much for the explanation. Makes a lot of sense!
I will start by "upgrading" the power supply to a new one (still have not recieved the polarity changer) and keep and eye out for the ePower.
Has any body changed the heat sink on their Nick? Mine was very firmly connected.
Btw: cutting a bit of the key membrame solved that. I now have all keys up and running :-)
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Btw: cutting a bit of the key membrame solved that. I now have all keys up and running :-)
Be careful with next opening, i reached that time few years ago when i could not cut more :D , fortunately since then i have new membrane.