About 100 watt Plexi and SLP

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Tesno
Junior tube assistant
Posts: 8
(2/28/04 1:59 pm)
 About 100 watt Plexi and SLP
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Does Doug sell the bridge rectifier needed for a 100watt Plexi?

Why is the CT of the secondary side going in between the first two 100uf caps?

In the old 100 watt SLP there is two caps in between the secondary side of the PT before the rectifier that connect from one HT leg to the CT two caps same for each HT leg, what is the reason for this?

Thanks!


Life is a jest and all things show it, I thought so once but now I know it.
 
6G6
Junior tube assistant
Posts: 97
(2/28/04 3:05 pm)
 Re: About 100 watt Plexi and SLP
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 The CT beween the filter caps is sort of a mystery.
I read somewhere recently that it appeared that Marshall was going to use that point for something, didn't do it and just left it that way.
As to the bridge rectifier, try four 1N4007s. Cheap, simple, effective.
 
GroundhogKen
Forum Moderator
Posts: 2301
(2/28/04 4:40 pm)
 Re: About 100 watt Plexi and SLP
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 The center tap of a bridge rectified HV secondary is 1/2 B+.

The center tap is tied to the junction of two series capacitors to insure that both capacitors get half the total voltage--rather than the entire B+ appearing across one cap. This arrangement means that the bleeder resistors that are typically found across series sets of capacitors are not necessary.

It's not a mystery; it's just not obvious at first glance.

Ken
 
GroundhogKen
Forum Moderator
Posts: 2302
(2/28/04 7:05 pm)
 Re: About 100 watt Plexi and SLP
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 And...

the two .22 uF caps that are shown on this schematic are for spike suppression.

www.drtube.com/schematics.../1959u.gif

Doug doesn't use them on his layout.

Ken
 
6G6
Junior tube assistant
Posts: 98
(2/28/04 8:18 pm)
 Re: About 100 watt Plexi and SLP
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 Hey Ken,
I saw some Marshall site that went on & on about what they thought that 1/2 B+ tap might be for.
I guess Leo wasn't the only guy to look for ways of saving on parts.
It makes sense.
 
aerojazz
Senior tube assistant
Posts: 144
(2/29/04 12:41 pm)
 Re: About 100 watt Plexi and SLP?
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 NEVERMIND: I just saw the newer layout. I was starting this project with stuff I saved from Dougs site a year ago.
 

Thanks

Edited by: aerojazz at: 2/29/04 1:09 pm
 
 
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