sb200 advice

[oh8jep]

Hello from Finland!

I have homebrewed some tube linear amplifiers,and always when made the power supply  with several  elcapasitors  in serial
I have had to "run up" first the elcaps (always that also when they are new ones,and the same if the amplifier has been stand by several of years without powered on). That is ,I have done so that first made rectifier board ready,the elcap pack ready,
then conected that normally with hightension transformer,BUT that is important,nothing else but elcap pack,not any other
load,amplifier circuit etc. Then finally connected normal  220V  (or 110-125V in USA) lamp in serial with wall lead,coming to primary of the hightension transformer. After that I have been "run up" the capasitor pack during the one night,and then measured over any capasitor separately how much is the tension how many volts,and if all the capasitors has been OK at the beginning the tension over any capasitor will be aproximately the same.
If so you can take off the lamp in serial the wall lead,and drive directly abt 2-3 hours ,following all the time if the situation 
of the tension over the capasitors will be  OK.

Now after that period you can connect your power supply normally to the amplifier and begin working.
Notice,this must be done always when you change some of the capasitors of the elcap pack.

I am sure this helps for your problem if anything else is OK in your power supply.

Best 73 de Aatos OH8JEP

----- Original Message ----- 
From: "rayfri" <rayfri at NETWORLD.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Saturday, March 09, 2002 11:48 PM
Subject: sb200 advice


> Need some advice from wiser heads than mine.....
> A friend of mine was given an sb 200 amp which had been sitting around
> for almost 10 years.  We fired it up and it popped the circuit breakers
> in the
> amp.  Pulling out my ohmmeter, I confirmed my suspicion when I found one
> of
> the six filter caps showed a dead short.  I checked the others using the
> quick
> and dirty ohmmeter test and they seemed to be okay.... no dead shorts.
> I also checked both doorknob caps while I was inside and they appeared
> to
> be okay.  Likewise with the rectifier diode strings.....
> I replaced the filter capacitor and we fired it up again.... and popped
> the
> circuit breakers in the amp again.  Is it possible that while the caps
> arent showing
> a dead short, one or more may be breaking down and shorting under
> voltage, but
> still show good with no power applied?
> Any other suggestions as to what I can look for?  It's not shorted tubes
> because
> it does the same thing with the tubes pulled.
> Also.... wasnt there someone who was making replacement power supply
> boards
> for the sb 200?
> Thanks in advance for your help guys.....
> Ray  wa7itz
> 
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