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 E.H. SCOTT All Wave 23 power supply/amp problem

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captal



Posts : 3
Join date : 2010-10-21

PostSubject: E.H. SCOTT All Wave 23 power supply/amp problem   Thu Oct 21, 2010 10:46 am

I have aquired an early E.H. Scott A/W 23 console.
I replaced all the caps and resistors in the p/s and put in tested tubes.
The chokes tested ok.
On turning on the p/s it blew the 5Z3 30 mfd filter cap.
I replaced it with another which also blew.
I double, triple, quadrupled checked all the wiring.
I have not connected the speaker or radio set plugs or put in the four 2A3 tubes.
Is it possible that this condition is normal if everything is not connected??

Can the p/s be run as a stand alone or must all be in place?
Would appreciate any help in this matter.

Tnx,
Al
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N7RHU



Posts : 3
Join date : 2010-10-12

PostSubject: Re: E.H. SCOTT All Wave 23 power supply/amp problem   Thu Oct 21, 2010 12:44 pm

Al-
With no load on the power supply, the DC voltage on the filter cap will reach 1.4 times the AC voltage ahead of the rectifier. This may exceed the rated voltage of the electrolytic cap.

One other possibility: the polarity markings on some tubular electrolytic caps can be confusing. Be sure you know the polarities of the capacitor leads, and that they are connected correctly.

--Chuck
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captal



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Join date : 2010-10-21

PostSubject: Re: E.H. SCOTT All Wave 23 power supply/amp problem   Thu Oct 21, 2010 1:04 pm

Thanks for the reply Chuck,

I was especially careful about the polarity of the caps because Scott used a rarely found sybol for electrolytic caps. A triangle denotes + and a straight line is for -.
I used this configuration for the other two filter caps without any problem.

Al
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Johnnysan



Posts : 64
Join date : 2010-10-12

PostSubject: Re: E.H. SCOTT All Wave 23 power supply/amp problem   Thu Oct 21, 2010 1:32 pm

There's really only 3 ways to blow up caps: Over-voltage, reverse polarity or AC on a DC cap.
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Tube Radio



Posts : 31
Join date : 2010-10-12

PostSubject: Re: E.H. SCOTT All Wave 23 power supply/amp problem   Thu Oct 21, 2010 6:28 pm

Replace the cap (if not already done), plug everything in and then turn on power. Everything should be ok then.
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captal



Posts : 3
Join date : 2010-10-21

PostSubject: Re: E.H. SCOTT All Wave 23 power supply/amp problem   Thu Oct 21, 2010 7:07 pm

Thanks guys for putting me on the right track.
Everone had the right answer, there must be a load or the voltage goes sky high.
I thought I read the manual carefully except for the back cover page and it clearly said that all plugs must be in place or else serious damage will happen to the p/s.
This is more fun than a barrel full of monkeys!

Thanks for all the help,
Al
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