Thanks for these additional thoughts, Tom.

I'm saving them for future reference, so that I have them available if I can
find some local help to address the problem.

Tom Behler: KB8TYJ


-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Tom Fowle
Sent: Saturday, November 28, 2015 1:01 AM
To: [log in to unmask]
Subject: Re: RS35 Transistors

It is just possible that each of the 4 transistors has a seperate emitter
resistor. These might be very low resistance value high power resistors one
from each emitter to a common point. This helps ballance current flow
between the transistors.

If one or more of these resistors were open, it would keep that transistor
from carrying any of the load current.

Also if replacing the transistors, there might be insulating washers between
the screws and the heat sinks. You must assure that none of the transistor
cases is shorted to the heatsink on which it's mounted. You need heat flow
there not current flow.

I aggree with Buch, replace all four transistors if any appear bad. But I'd
do my best to replace with the exact number unless you are really able to
compare specs.
Tom fowle

On Fri, Nov 27, 2015 at 03:08:43AM -0800, Butch Bussen wrote:
> The hot ones are likely good as they are in series with the load, that 
> is why those supplies are called series regulaters.  I'd replace all 
> four from the same vendor so you have sort of a matched set.  Should 
> be able to get those from mouser or some one.  You will also need some 
> silicon grease.  When you pull the transisters, watch for the thin 
> mica insolater that is between the chassie and transister.  Some times 
> these stay stuck to the chassie, or heat sink, and some times they 
> come with the transister.  You don't want the transister actually 
> touching the heat sink.  A small bit of silicon grease is used between 
> insolator and transister and between tinsolator and heat sink to help 
> with heat transfer.  I'll have to see if I can find the number, but if 
> I were doing it, I'd go with darlingtons, I think e c g 247 or e c g 
> 249 which are the same, but higher current.
> 73
> Butch
> WA0VJR
> Node 3148
> Wallace, ks.