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IBM 5154 Monitor troubleshooting

Z

zamuel_a

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Dec 27, 2020
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11
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Sweden
Hi

I just got an IBM 5154 EGA monitor that I can't get to work. I get an image as on my picture:
ega 5154.jpg

I have replaced the C311 capacitor and also replaced the TDA 2653A chip, but with no difference. I have also replaced all capacitors in the power supply. The capactors all look good but to be safe I replaced them. I have turned the pots in the back of the monitor back and forth and it change the image a little but not so that it works. I can't really find any more information on what to look for.
 
Not to state the obvious, but are you positive you're feeding it an EGA signal? That the card it is connected to isn't sending an MDA signal by mistake?
 
I can't say for 100%, but it is the card that came with the computer and according to the previous owner it was working when he tested it. Something probably went bad during shipping or when he turned it off last time (it hadn't been on for years before that). I have tried it with another EGA card and got the same result. I'm not sure if there are any settings on EGA cards so they give out MDA signals?
 
zamuel_a said:
I'm not sure if there are any settings on EGA cards so they give out MDA signals?
Click to expand...
The IBM EGA card has switches, and one of the switch combinations gets the card to output MDA signals. See [here]. Many third party EGA cards also have switches (although which switch does what varies between cards).

I remember fixing someone's EGA card where the problem was a 'dirty' switch. Fixed by using some switch cleaner together with flicking the switches many times between off and on.
 
Just wanted to make sure you knew what card you were running. If it's the same card the previous owner verified, it should be fine.

Hugo Holden on this forum might be able to help.
 
The 5154 VDU, if working normally, can display CGA or EGA images.

So the first move (in the absence of a scope to check the sync and video signals) is to have a known good signal source that works on another VDU.

(The MDA H scan frequency is not suited to it, just CGA and EGA as pointed out).

If you have a known good signal source out of the video card in the computer, 15.750 kHz H scan rate for CGA and 21.85kHz for EGA (checked with a scope or another VDU), and the 5154 VDU doesn't display it correctly, then it is time to go inside the 5154 monitor, with a scope, to figure out what has gone wrong.

Since the EGA signal has an inverted V sync pulse (compared to CGA) the circuitry in the 5154 automatically detects this and changes into EGA mode, the higher scan rate mode.
 
I connected the monitor to my commodore c128 CGA output and it shows the same image. I can see text but it's squeezed. Also if I just turn on the monitor without connecting it to anything I get around half an image. I might try and replace all capacitors on the main board. I replaced the ones in the power supply and since I see an image I guess it should be fine. The logic part is probably not an issue either I guess since I can see something.
 
I was able to repair it! I replaced all capacitors on the main pcb and after that it worked! I couldn't see any obvious bad capacitors and I measured their capacitance and it was fine. Didn't measure ESR so maybe that was wrong. Anyway, now it's working again!
 
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