Was: The Oscillator. Now -the Green Machine Lives

[TomMcNally]

Steve ...

You should be able to rotate the chokes "hot" and hear a change.
Use some rubber gloves !

... tom

[kheper]

The audio quality of 'Tom's live feed' was
pretty good. I compared it a local broadcast,
running thru my Marantz 125 tuner.

The vocal portions of Tom's feed were
definitely more 'nasal' and cold than
the Marantz's, but considering the very poor
quality of most net feeds, it surpasses them.

[Shannon Parks]

I'm not sure what the optimal method for grounding is when using the SDS supply, but I think I would star everything back to the SDS board, and have one wire then go to the chassis (and not use a safety ground either). Maybe just start by disconnecting the red board from the ground buss and running a wire from the red board to the SDS.

[SteveH]

Guys,
Last night I set the chokes back in the chassis in their new rotated positions; grounded the inputs, and fired it up. Damn near dead silent (you need to put your ear up to the speaker to hear any hum). So I then hook the PAS to it and have hum in the right channel Yellow_Light_Colorz_PDT_14
So Im not sure what this quite means yet. I need to swap the interconnects and see if the hum follows the one channel coming out of the preamp or not....

[kheper]

If you get no hum with the inputs shorted on
the 'green' amp, then the problem is
'upstream'.

Some st70 purists maintain that you should
never use a 3 prong power cable in the amp.
A two prong polarized is recommended.

Try another preamp or source. A CDplayer
with a variable volume control, for instance.

[SteveH]

Will do....
Just interesting that the preamp doesn't gimme any hum when I have it hooked up to my ST35 or my Compactron. Either way I'll have to mess with it more when I get back home at the end of the week.

Thanks again,
Steve

[SteveH]

Guys,
Well I tracked down the hum - it was due to three main reasons:

#1 - Bad interconnect. Due to the angle at which it was bent; I guess it wasn't making good internal contact to the connector. The minute I replaced it; the hum dropped 50%.
#2 - Getting the chokes off of the same plane as the power tranny. This helped quite a bit too - I just wish I could have rotated them more.
#3 - There is still some hum coming out of my PAS; but at this point you need to have your ear about 4" away from the speaker to hear it.

Thanks again to everyone for their help !