Re: VECTOR: Go5/801 probs (Asteroids)

On Wed, 29 Dec 2004, David Pinckney wrote:

> Yes i did check all cables, i'm pretty sure its a deflection board problem,
> somebody gave me a link to Go5 faq's and it says that in x y circuits some
> transistors can meter good but in fact be bad, so it might pay me just to

I wouldn't worry about that, it isn't at all common for that to happen. I 
would read the FAQ again though. Maybe a few times.

I very much doubt you have a transistor problem. The deflection transistors 
are used in pairs. For each axis, there is a transistor for positive 
deflection and one for negative. To loose all Y delfection at once, both 
transistors would have to die at the same time, which doesn't usually 
happen.

It is far more likely there is an inturruption in the Y signal someplace, so 
I would again check the cable, the Y pin going to the board. Again, the 
simpelest thing is to use a scope and make sure you have a signal at the 
input to the board, then trace the signal path and see where it disappears.

If you don't have a scope, 1) Get one, it will make Vector game ownership 
that much easier. 2) A logic probe is cheaper and may work in this case. 
Personally I've never found them usefull, but others swear by them. 3) Page 
21 of the FAQ has a voltage table for all transistors when the test pattern 
is up on the screen.

The problem with shotgunning these old boards is you increase the chance of 
lifting a trace and causeing a new problem for yourself. You know the 
problem -- no Y signal. The easiest thing is to start where you know there 
is signal, follow the path, and see where it stops.


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Chris Candreva  -- [email protected] -- (914) 967-7816
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