Re: Amplifone help needed

jwelser@ccwf.cc.utexas.edu wrote:

>
> Check your Video B+. It's supposed to be 180V. The installation
> instructions (the original Atari ones, at least) say that after installing
> the new HV transformer you should "Adjust the frequency of primary
> switching to get a video B+ of 180V" You use R7 (I think that's it
> -- it's the pot near the 555 timer) to do this. I'm thinking that your
> colors might be overdriving because the Video B+ may be too high. I have
> a similar problem (Deflection seems good, but I only get bright, white
> vectors) that I've shelved for the time being, and it is definitely a
> deflection board problem (My heater doesn't glow any different from
> normal, though...)

I didn't check the B+. Though, since the B+ is also controlled in the
same manner as the HV, and the HV is correct, how can I change the B+
(If it is too high) without affecting the HV? That is, is it more
important to have the B+ at 180V, or the HV at 19.5K? (I did exercise
R7 and lowered it all the way but the problem did not get any better).

The problem that you describe with your hardware sounds exactly like
what's going on here. I know that the deflection boards are good. They
worked perfectly before I had this brilliant idea .. :-( It seems that
the HV/B+ is the only adjustable voltage. What's left to do?

>
> It's wierd that you're getting proper HV and bad heater voltages,
> since they both come off of the HV transformer. Since you didn't mention
> messing with R7 you might try it and see. Did you measure the heater
> voltage, just for kicks?
I didn't measure the heater voltage. Any idea what it should be? I'm
assuming something around (6.3 to 7VAC), since it needs to be compatible
with the WG tubes ... and that's about what they use.

Thanks for the reply.

Joel-
Received on Mon Nov 3 08:42:28 1997