[TenTec] Herc II vs Astron

[Tom Macon]

Looking at the 420 schematics, it seems the backfeed must come through the 
dump resistors.  If one ps is on with the other 3 off, the backfeed voltage 
shows up on just one supply output - the other 2 remain at zero.

I still use the 9420's 81419 board,  with the Astron line inputs connected 
where the transformers were.  And the Astron outputs go individually to the 
amp cable as they did with the old supplies.  The 14v/3A is derived from 
each supply in the same manner it was originally - through 4 isolating 
diodes that I added (since the old ones are gone).  This seems to work fine 
and I don't see any backfeed between supplies when the Herc is not 
connected.

I adjusted the 4 supplies to 14.0v, within a few mv.

While the manuals have all the schmatics, etc., there is no written theory 
of operation.  Does anyone know if this exists anywhere?

 - Tom, K9BTQ


----- Original Message ----- 
From: "Ken Brown" <ken.d.brown at hawaiiantel.net>
To: "Tom Macon" <tmacon at wi.rr.com>; "Discussion of Ten-Tec Equipment" 
<tentec at contesting.com>
Sent: Sunday, March 03, 2013 1:35 PM
Subject: Re: [TenTec] Herc II vs Astron



> 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