Anything else I should check before I replace the jungle IC?

[berniedd]

My 15-inch Mag CRT monitor (model D510) first started its symptoms with an intermittent loss of vertical sweep (single horizontal line across the screen) for only a second or two, then return to normal. Days later, new symptoms appeared: the picture would shrink to 2/3 of its original size, be off-center, and come with a decrease in brightness. At other times, the picture width and height chnge intermittently. Sometimes it would return to normal, sometimes it wouldn't. Although there is still good synchronization and the picture is still intact, it's getting such that I can't do much work with it. I suspect it's the jungle IC - STV7778. Before I replace it, is there anything else I should check? It's an expensive chip, has 42 pins and is such a bear to work on.

 

[mstechca]

You might be better to get a new 15" CRT monitor.

I have seen local ads in the paper where you can get an old computer system with a monitor for $50 cdn.

Sometimes, you might find people throwing their old computers out including the monitor :shock:

So why not go to their lot, the day before bulk pick-up day and take the monitor out of their garbage. :wink: After all, it is free!

Your idea costs money, and could potentially cost you (at least part of) your life if you are not careful (for example: fixing the monitor while it is on)

 

[nsklavos]

Give the solder connections on the pcb a good lookover, especially around components that get hot (high wattage resistors, rectifiers, power transistors, etc). I have repaired several things that just got warm, then cold, one too many times.

 

[Nigel Goodwin]

I would agree with nsklavos, it sounds more like a dry joint (cold soldered joint for our American readers), rather than a component failure.

 

[berniedd]

Yup, I'll try resoldering joints that look suspicious. Thanks all for the input. I'm trying to fix it myself because I like a challenge and look forward to learning something for the experience. I'm not a serviceman, just a hobbyist. And thanks for the concern; I know where high voltages are present and discharge them with my multimeter (set to the appropriate voltage range).

 

[berniedd]

Well I finally changed the jungle IC and this cured the decreased brightness problem But the picture problem is still there. Actually, it's as if the monitor is changing resolution settings at random. I can use the horiz and vert size controls to bring the shrunken picture to fill the whole screen again, but in a few secs, the picture becomes too wide and I'd have to readjust the size controls again. I'm beginning to suspect the microprocessor IC. What do you guys think?

 

[Hero999]

I agree with mstechca, it probably isn't worth repair, but I can understand you wanting to repair it to learn more about electronics there again there are far more fun and interesting things to play around with, my advice get a new one, perhapps you could opt for a TFT screen they're great.