Re: Amplifone Design... Wonders me

I'm going to say your problem isn't ripple, it's more likely to be the
degauss circuit never turning off. By supplying DC instead of AC you
basically stopped the degauss coil from putting out an AC field.

Try it on AC with the degauss coil unplugged and see what you get.

mypearl wrote:

> Hello Group,
>
> I've been posting before about my Star Wars with amplifone that is
> giving me a wobbling image.
>
> After a lot of testing and replacing old components on the amplifone
> deflection board, I found that If I connect my regular lab power
> supply to the amplifone's + and - 30V rails, the wobbling goes away
> and the picture is rock-steady! I just connected the + and - 30 VDC to
> the AC power input on the Deflection board.
>
> This means the Amplifone (or mine) isn't very good in rejecting power
> supply ripple.
>
> The ripple on the supply rails is about 200 mV AC RMS, what doesn't
> seem to be extraordinary considering the currents involved.
>
> I understood from someone that the biasing transistors Q3 and Q13 are
> extremely of influence when it comes to power supply ripple, but that
> section seems fine and I've replaced both the 3904 and the MPSU57, as
> well as the 914 diodes (by 1N4148's) on both channels. I also
> installed 10.000 MFD capicators with low ESR specs for the main filter
> caps.
>
> I cannot believe the image on every Amplifone should be wobbling
> somewhat. Can anybody confirm that it should be very stable?
>
> What for Atari's sake could cause the deflection board to be so
> sensitive to power supply ripple?
>
> Being very curious!
>
> Mendel Pearl
>
>

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Received on Tue Mar 9 15:39:39 2004