Rasterlist Archives: Breakout PCB & Motorola monitor

From: Paul Sommers <Paul.Sommers_at_cwo.com.au>
Date: Sun Sep 24 2000 - 21:01:21 EDT

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<TITLE>Breakout PCB & Motorola monitor - questions for everyone!!!!</TITLE>
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Gang,

The sad history of my Breakout is that the transformer caught on fire about a year ago (smoke everywhere - the fire brigade actually turned up because I opened all windows and doors for the smoke to get out).

I have now replaced the transformer with two others (one for 110vac and one for 16.5 and 6.3 vac).

It looks like the board got spiked because it was working fine to that point - now I have monitor and board problems that I've got some questions about.

1. I have replaced all the lytics on the monitor board, and it made no difference. I'm getting continuous waves through the picture. I don't believe they are hums bars. Just waves of greyscale. If you adjust the brightness and contrast to SOLID black and white - it is almost un-noticable. The waves move across the vertical screen right to left.

There are an awful lot of polyester caps on the board. Very old. Should I replace these or look for something else.

The thought has occurred to me it may be coming from the PCB.

2. There are three caps of 50uf. The schematic lists these are polyester, but these look lytic. It doesn't look like a repair - or it was done long enough ago all the solder matches.

I can't find 50uf caps anywhere in Australia. How would I go with 47uf. Just how much tolerence do these things have.

Should I follow the original schematic and change them back to poly's.

3. While we're on caps. The big 8000uf at 16v that is one the board looks pretty old. But the only 8000uf cap I can get in Australia is 80v and it is a surface mount. What a pain - not to mention expensive. Can I put a couple of lower value caps which make up 8000uf in series or parallel instead???

4. The paddle is shaky. It's okay when it is hard right, but as you move it further left you get very very shaky double and triple images. I'm wondering whether the main 8000uf cap which does the power filtering could cause this, as the paddle is the only part of the circuit (except sound... blip) that uses analogue components. I have replaced the 4016, 555 and the pot with no effect.

5. I'll work this last one out eventually.... I have only half a brick in the first column (left hand side). Just thought someone may have seen this before.

Phew! It seems a lot, but I've brought it back from the dead and started getting tired of working it out myself. Hopefully someone can help me on one or more.

Thanks
 MacMan

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Received on Sun Sep 24 19:14:04 2000

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