[Collins] 30s-1

[Dr. Gerald N. Johnson]

I just dug into the two 30S-1 manuals in this computer. I see the '64 
and '76 editions both show using selenium rectifiers for the bias supply 
and the step start delay. Those parts are way beyond their working 
lifetime and are showing increased series resistance and reverse leakage 
to lower the voltage under load and apply reverse polarity pulses to the 
electrolytics which can't stand that abuse. They should be replaced by 
something like 1N4004 or 1N4007, basically half amp or better current, 
400 volts peak inverse voltage or better. These particular numbers are 
easy to find and often can be had for a few pennies each. They can be 
mounted on two lug insulated terminal strips. Or three lug with the 
center lug grounded and the mounting foot. Same as in the bias supply in 
the 516F-2.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 11/25/2015 4:44 PM, Björn Magnusson wrote:
> Hi.
> I have a Collins 30s-1 and I have a problem with it.
> When I start it up and wait a few minutes to get it warm the bias is correct.
> But when I start to transmit the bias will slowly goes down.
> And after a half of a minute it will only come up to approx 0,1 on the multimeter.
> If I change to call mode the bias is correct.
>
> Do you have any idea of what the problem might be? I have checked the electrolyte capacitors that I can think Bill be wrong with but they seems tone ok.
>
> Thank you.
> Best regards Bjoern.
> 73 de sa6axu.
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