[TenTec] Herc II and SMPS and TenTec 9420

[Bob D.]

Hi Gary-

I used a surplus computer server switching supply on mine for a good while.
I like having circuit diagrams for my gear and after some effort and no
success in finding one switched over to a battery supply. The switching
supply was very quiet. They are nice because they hold output voltage over
a really wide range of inputs.

It would be self serving of me to advise you to let it go as I am looking
for a 9420 reasonably close to Atlanta:-). My Herc II is a later model with
2sc2879 transistors. I'll be comfortable with a 9420 and OVP limit at 15 V.
A crowbar should do the trick. I would definitely NOT use the 9420 or any
linear supply without protection. Squirrels chewed through my neutral on
the AC service drop and took out a $300+ variable speed drive. Neutral has
been spliced three times because of squirrels.

I'm not familiar with the transistors used in other versions of the Herc II
but will be surprised if any would be damaged by 15 V.

My advice. Keep the 9420

73, -Bob

73, -Bob ah7i



> Message: 5
> Date: Sun, 2 Jun 2019 04:50:27 -0400
> From: Gary Hendricks <k4mt1950 at charter.net>
> To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
> Subject: [TenTec] 9420 VS Switcher
> Message-ID: <7e01f6c1-c30e-7894-bd10-7881d9520e68 at charter.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I have been looking at the schematic for my 9420 supply and it looks
> like the output of the series regulators have no over voltage
> protection. If my memory doesnt fail me I think when I was working at
> TenTec I remember hearing the service guys talk about pass transistor
> failures on this supply being somewhat common.
>
> Has anyone used one of the high current switching supplies on the
> Hercules II amp? I see some avail at 14 volts and 100 amps with every
> protection built in.
>
> Thinking about letting 9420 go and using one of the switchers because of
> the protection built in
>
> Thanks
>
> Gary K4MT
>
>
>
>