[TenTec] Using Non-TT Supply

Wed Aug 28 01:55:44 EDT 2013

Jerry, there are 2 different purposes for over current protection.

The common thinking (and use) is to protect the power supply itself when an
unsafe level of current drain is approached, especially in the case of a
accidental short circuit.  This needs to react fast.
The over 'voltage' protection protects the transceiver from being damaged in
the case that the power supply breaks and puts out too much voltage.

In OLDER T-T transceivers also used the power supply's over-current
protection as an additional protection to protect the final transistors in
their transceivers.  This method was used up through the Model-962.  

The current drain of the transmitter when running 100w is not always the
same.  It also depends on the load of the antenna (or rather the impedance).
It is happy at some number when loading into 50 Ohms.  For example, let's
say 18A.  However if the antenna happens to be a short vertical on 80m, it
may have an impedance of about 15 to 20 Ohms.  If you continue to run 100w
into a lower impedance, the current goes up.  At some point it becomes
dangerous.   The (older) T-T power supplies would shut down before that
point was reached.  This was a VERY safe and reliable way of doing it.  But
the world changed...

YES, the electronic circuit breaker is faster than a magnetic circuit
breaker, but the magnetic circuit breaker was used to protect the final
transistors in the transceiver.  The transistors didn't just pop at the
first sign of over current, but would burn up if used that way for a longer
period of time.  The speed of the magnetic circuit breaker was just fine for
that purpose (and arguably more reliable). 

Transistor PAs in the transceivers remained the same at Ten-Tec for 30
years.  It didn't change until about the 2nd year of production of the
Orion.  At that point they switched from bipolar transistors to Mosfet
transistors...in the middle of the life cycle of the Orion.  Why?  Certainly
not for technical reasons.  Never touch a running systems.  The transistors
became obsolete.

The over current ratings of the power supplies kept going up.  Was 18A, then
20A, then 22A.
Reason:  RX current drain kept going up with each new transceiver.
Therefore the level of trip for the over current protection kept changing.
My guess is, that's the reason T-T abandoned that form of protection for its
PA's.

73
Rick, DJ0IP

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Jerry
Haigwood
Sent: Wednesday, August 28, 2013 6:39 AM
To: 'Discussion of Ten-Tec Equipment'
Subject: Re: [TenTec] Using Non-TT Supply

Hi Rick,
    Don't forget that in the early days, TenTec used to use magnetic circuit
breakers to protect finals.  I am not sure how fast the breakers were but
they can't be faster than electronic current limiting.  I use a smaller
Astron switcher power supply.  It is rated at 18 amps maximum and will go
into current limiting at 20 amps.  So far (2 years now), I have not had any
problems.
Jerry W5JH
"building something without experimenting is just solder practice"

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Rick -
DJ0IP / NJ0IP
Sent: Tuesday, August 27, 2013 11:29 PM
To: 'Discussion of Ten-Tec Equipment'
Subject: Re: [TenTec] Using Non-TT Supply

Paul,

The over current protection in your RSM 35 is not the same as the over
current protection used in the Ten-Tec power supplies.  The RSM 35's over
current protection is to protect the power supply itself.  The Ten-Tec power
supplies had their over current protection set to exactly the maximum
permissible current for the transceiver's finals, and that helped protect
the final transistors.  Ten-Tec used this method for almost 20 years.  I
think the Omni VI was the first transceiver which did not rely on the power
supply for the extra protection.

There is nothing special about the Ten-Tec circuit, other than the point at
which it shuts down.  Older models ceased at 18A, later ones at 20A (as the
new transceivers required more current).    Any good power supply with an
adjustable current parameter would also work like the Ten-Tec power
supplies.  However how often do you see someone using a P.S. with an
adjustable current limit?

Bottom line, your suggestion is only good for the newer transceivers.  Don't
use it with the older Omni's or Corsairs.

73
Rick, DJ0IP

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Paul
Kraemer
Sent: Tuesday, August 27, 2013 11:46 PM
To: tentec at contesting.com
Subject: Re: [TenTec] Using Non-TT Supply

John
I use Astron RSM 35 with all my solid state radios including OMNI VI Very
good supply with overvoltage and over current protection Paul

--------------------------------------------------
From: "John Farler" <k4avx1 at windstream.net>
Sent: Tuesday, August 27, 2013 3:21 PM
To: <tentec at contesting.com>
Subject: [TenTec] Using Non-TT Supply

> My supply for the TT Omni V or VI has problems.  When I tune up, even 
> to a dummy load, the pilots in the radio dim and output is not where 
> it should be on 40 meters and up.
> Current is less than 20 A, but I haven't checked the voltage drop yet.
> 
> My question is can I use a non-TT supply with the Omni VI safely?  I 
> remember someone on the list saying TT stopped using the original type 
> of power supply like the one with the old Triton which kicks of at a 
> certain current, but I can't remember which radio it is that doesn't 
> depend on the "circuit breaker" type of protection.
> 
> I have several non-TT supplies that will provide the current and more
> - is it safe to use them with the Omni V, VI??
> 
> I'm guessing the filters in the power supply have gone bad...actually 
> it has 3 in parallel.
> How can I check for one bad one, or can I?
> 
> Thanks, and I hope my post is not too confusing....
> 
> John, K4AVX
> k4avx1 at windstream.net
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
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