Need advice on ibm ega 5154 crt, fuzzy washed out picture

Discussion about old graphics cards, monitors and video related things.

Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby lowlytech » 2018-6-13 @ 01:13

I got a 5154 that wouldn't turn on at all. Took it apart and litterally recapped every single cap on all boards. The power supply had never been opened and one cap failed open while another two had very puffy tops. The notorious x2 caps hadn't released their plume of smoke, but replaced them while in the unit. Got it back together today and testing it the screen was very washed out like the brightness was turned up all the way. The 25kv tripler was already turned all the way ccw, but adjusting this makes the screen even brighter and blurrier. Adjusting the screen control down to almost the darkest setting gets the text readable, but it is so dark the white kinda looks blue.

Does this sound like a symptom of a bad tube or do you think i need to change the flyback/tripler? In my mind the adjustment on the tripler would fix my issue if i could get another half turn, however it has hit it's stop.


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How the screen looked after recap. Brightness seems good, however the focus is extremely blurry and washed out.



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screen turned up 3/4, focus on tripler/flyback still at minimum brightness


20180612_193654.jpg
Screen control turned down very low, text is sharper, but still very dark.
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby Shagittarius » 2018-6-13 @ 06:03

Hmmm...When I had my 5154 monitor working for about 10 minutes before it smoked again I might have seen something similar to your text issue. The monitor seemed to have a problem with the half bright colors but not the full bright colors. Can you check and see if your fullbright colors are fine while the halfbrights are too dark? Since I am getting my monitor repaired I will keep you informed on what I find out and share info.
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby lowlytech » 2018-6-13 @ 18:47

I haven't tried anything but a DOS text mode on bootup. When I saw the text was horribly fuzzy that kind of stopped me in my tracks. I tried adjusting the pot on the power supply to end up with 12V on IC2 output, but with it cranked all the way over I am getting 11.9v which I assume is alright. Turning it the other way drops the voltages down to about 8 volts on that pin.

I will have to get some color bars or get check-it installed soon just to see. I hope you can find out what may be wrong. I suspect the HV components, but I don't know much about the fundamentals and symptoms of CRT's unfortunately. I have no TV repair shops in my area and I have checked with about a dozen people and I can't even hunt down a high voltage meter to take accurate HV measurements.
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby MMaximus » 2018-6-13 @ 19:39

Have you tried playing a game on it yet? On my 5153 the text mode looks quite blurry compared to vga text mode, but 320x200 graphics look great on the other hand.
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby lowlytech » 2018-6-14 @ 01:56

MMaximus,

No I haven't ran anything but a standard DOS console. I will have to try to get some other video modes ran on this before too long.
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby Jo22 » 2018-6-14 @ 03:22

lowlytech wrote:I got a 5154 that wouldn't turn on at all. Took it apart and litterally recapped every single cap on all boards.

I see. Did you also replace any diodes or resistors, too ?
I'm not sure if these two things are related, but when I repaired old stuff like PSUs,
failing diodes where the second biggest issue besides aged caps, followed by burned resistors.
As I said, not sure if that applies here. Repairing monitors is something I did rarely do before (excluding LCDs. I replaced one in an original GameBoy).

Edit: There's a test program called "Testbild", which draws an calibration pattern (EGA/VGA).
It uses normal, native graphics modes, however. 640x350 or 640x480 instead of 320x200 low-res mode.
viewtopic.php?p=614267#p614267

If you need a 320x200 test program, the CGA Compatibility Tester might be useful.
It's meant for CGA cards, but displaying one of the calibration patterns might work.
viewtopic.php?t=28983
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby lowlytech » 2018-6-14 @ 05:09

Jo22,

I did not replace any diodes, transistors, or resistors. Infact the boards looked pretty good considering their age and there were no "cooked" looking areas. Do you think a bad diode could cause the monitor to function with an excessive blur, but otherwise everything else seem to function ok? If so i can start pulling diodes to test. I just figured if it was a diode I wouldn't get any picture or something else would just not work at all. The one cap that failed open I marked in the picture which is directly connected to a diode. All the other caps i pulled I ran my ESR tester on, and surprisingly their values were still pretty much in spec.
653B_145.jpg
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby Jo22 » 2018-6-14 @ 05:33

lowlytech wrote:Do you think a bad diode could cause the monitor to function with an excessive blur, but otherwise everything else seem to function ok?

I'm sorry, I do know too little about monitor electronics to answer that. :(
It was just an idea anyway. From my experience, diodes are sneaky, that's why I mentioned it.
They can fail both completely or partially (slowly dying).

A few years ago, I repaired a simple in-house system (for phones, analogue and very old) we had at home.
The diodes would often fail after a given time. It became noticeable when we heard audio cracks in the phone line.
Over time, things became worse until the point that it nolonger worked (until I replaced the diodes).

Similar behavior can be observed on todays LED lamps, I believe.
When they start to flicker straight after beeing switched on, some of their solid-state parts (diodes mainly) are likely dying.

Anyway, I was just generally speaking.. Sometimes the cause for a malfunction could be a part someone would suspect the least.
In your case, it might be well something else, as well. Old CRT tube, (flyback) transformers, etc. I'm not sure.
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Re: Need advice on ibm ega 5154 crt, fuzzy washed out picture

Postby lowlytech » 2018-6-21 @ 04:41

Just a quick update. I got the 25kV tripler installed and that is what finally fixed the blurry text on the screen. I haven't tested any CGA/EGA graphic modes yet, but I plan to get all the fine tuning done hopefully this weekend. Thanks again to everyone that chimed in and all the help this forum provides with this great hobby and keeping all these older computers up and running.

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