Wow, doesn't sound good.  I've taken mine apart just to look and they're 
massive inside.  I actually had one I returned to a e s.  Just running 
with no load, the thing would run so hot it was uncomfortable to touch. 
For some reason, lots of hysterious los in the transformer.  The 
replacement was fine.
73
Butch
WA0VJR
Node 3148
Wallace, ks.


On Wed, 2 Apr 2014, Alan R. Downing wrote:

> Hi Butch.  I had a major failure in a 70 amp Astron linear supply several
> years ago.  Based on the smell that wafted out of it, I'd bet that it was
> momentarily on fire, HiHi.  I didn't bother to repair it, just sold it at a
> hamfest for $5 just to get rid of it.
>
> Alan/KD7GC
>
>
>
> Alan R. Downing
> Phoenix, AZ
>
> -----Original Message-----
> From: For blind ham radio operators [mailto:[log in to unmask]]
> On Behalf Of Butch Bussen
> Sent: Wednesday, April 02, 2014 2:25 PM
> To: [log in to unmask]
> Subject: Re: Power Supplies (Switching or Not)
>
> Yep, certainly possible, but I have used many many conventional supplies
> on my own station and in many commercial instalations, and I've never
> had the ovp fail.  If i replaced pass transisters, I always used
> darlingtons.  They genally opened rather than shorted if they went bad
> at all.
> 73
> Butch
> WA0VJR
> Node 3148
> Wallace, ks.
>
>
> On Wed, 2 Apr 2014, Martin G. McCormick wrote:
>
>> 	Another good thing about switching supplies is that they
>> ten to fail safer. Linear regulator supplies can end up with
>> shorted output transistors that put the full unregulated output
>> of the rectifiers and filter capacitors on your nice expensive
>> radios. There is usually a huge SCR with a circuit designed to
>> fire the gate of the SCR if the voltage exceeds maybe 14 or 15
>> volts which causes the SCR to short the output and blow a fuse,
>> but still that is pretty extreme.
>> 	What if the SCR blows first?
>> 	Switchers are more apt to just quit when something goes
>> wrong. They may also make smoke and blow fuses or capacitors but
>> they aren't likely to keep running and deliver high voltages to
>> the load turning it in to a hot paper weight.
>>
>> 	As for repairing switching supplies, the poorly-designed
>> cheapies will probably start cooking their electrolytic
>> capacitors and begin to die soon after purchase but well-made
>> supplies from good components should last decades. The
>> beginnings of a switching supply are very much like the power
>> supplies that used to run CRT-based televisions. They tend to
>> either be 100% up or 100% trash and they can switch from one
>> existential state to the other in a flash and I mean that
>> literally.
>>
>> Martin WB5AGZ
>>
>>
>
>