[TenTec] Herc II vs Astron

[Ken Brown]

> Upon investigation, it seems that one or more of the Astrons shuts down so not all four sections of the amp are powered.  I see that, if I turn off one supply, that there is backfeed from the amp showing up on its output.  My guess is that  the one of the supplies (a little slower to come up?) senses the backfeed voltage from another one and this triggers some protection feature.
>   
Perhaps so, but I see no way for the back feed to occur, except through 
some 100 K Ohm resistors on the DC Distribution Board. If that is enough 
to trigger a protection feature on one of the Astrons, then my guess it 
that one of the Astrons is mis-adjusted or is in some other way faulty.
> I have only the sheet that came with the Astrons - no schematic or detailed technical info.  Tomorrow I will call them to see if they can shed any light, meanwhile perhaps someone here has experience or insight?
>   
Some Astrons have a terminal which is used to tie the regulation 
circuitry to another identical Astron when paralleling them for higher 
current capacity. I'm not sure this would help though, since the 
Hercules II is really set up to run on four separate, not paralleled, 
supplies.

Neither the positive supply leads nor the negative supply leads are 
paralleled together in the 9420 or in the Hercules II, except when using 
the cable for battery operation. I suggest you keep the Astrons running 
independently, feeding the four sections of the Hercules II separately. 
You also need two other voltage sources, +REG and +14v/3A to run the 
control circuitry in the Hercules II. In the 9420 +14V/3A supply comes 
from the other power supplies, and are only paralleled via diodes 
(actually using half of some bridge rectifiers). The +REG supply has 
it's own transformer, rectifier, filter and regulator.

You really should check out the schematics of both the Hercules II and 
the 9420. Mine all came in one book, and even if you don't have a 9420, 
you may have a schematic for it.

If these are linear mode regulated Astrons, they are probably a pretty 
straightforward circuit using transformer, bridge rectifier, filter 
capacitor, LM723 regulator chip and 2N3055 pass transistors.

DE N6KB