I have been using an Astron 35M for all my shack 12 volt power since 1988.
This supply has been on continuously since 1988 except for when I power down
and disconnect during lightning storms. The supply has been used
extensively with an Orion, Orion II, Omni VII, Icom 756 Pro, Eagle, Pegasus,
Jupiter, Kenwood TS-570. I have never had any problem whatsoever with the
supply. It is so to say a brick sh** house.
Carl Moreschi N4PY
121 Little Bell Drive
Hays, NC 28635
www.n4py.com
----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
To: "Stuart Rohre" <rohre@arlut.utexas.edu>
Cc: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Monday, November 22, 2010 11:28 PM
Subject: Re: [TenTec] best power supply for Orion II and other items
> The failing in vintage Astron supplies is that the emitter resistors
> have too little voltage drop to force decent sharing so the transistor
> with the highest current gain gets most of the load. When it fries,
> usually burning off the emitter connection internally after the junction
> shorts and the crow bar protects the radio, that leaves one less
> transistor to shoulder the load. That progesses through the entire
> collection of pass transistors. It would be preventable if the emitter
> resistors had a larger value so to drop as much as a volt when each
> transistor is carrying its fair share of the load. E.g. 35 amp supply 6
> pass transistors, means each one carries almost 5 amps, and that emitter
> resistor needs to be 0.2 ohm to drop one volt. Last I noticed Astron
> resistors were more like 1/4 that value.
>
> 73, Jerry, K0CQ
>
> On 11/22/2010 6:56 PM, Stuart Rohre wrote:
>><SNIP>
>>
>> As Jerry says, the paralleling of transistors means if one goes, the
>> others can fail under the next load.
>>
>> -Stuart Rohre
>> K5KVH
>>
>>
>>
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