[Jukebox-list] Selenium Rectifier

[Don]

Thanks Wes.
I appreciate your lesson and review.
Don

----- Original Message ----- 
From: "The Jukebox Junkyard" <jukeboxjunkyard at cox.net>
To: "Jukebox mailing list" <jukebox-list at lists.netlojix.com>
Sent: Tuesday, May 01, 2007 4:00 PM
Subject: Re: [Jukebox-list] Selenium Rectifier


>    Don, all bridges have two full wave rectifiers inside. Both are used in 
> circuits that use transformers that are not center tapped.  There are 
> circuits that use center tapped transformers when you need both  positive 
> and negative supplies. This circuit is used in some high powered 
> amplifiers. Some use a large isolation capacitor to protect the speakers. 
> This capacitor is connected to the center point of the transistor output 
> that is at zero potential with no signal. This circuit was developed 
> before complementary pairs came into use.Personally I prefer this system 
> over later complementary circuits. They are easier to trouble shoot.  Some 
> of the capacitors have positive on the can common. Wes.
> ----- Original Message ----- 
> From: "Don" <dontutt at telus.net>
> To: "Jukebox mailing list" <jukebox-list at lists.netlojix.com>
> Sent: Tuesday, May 01, 2007 1:13 PM
> Subject: Re: [Jukebox-list] Selenium Rectifier
>
>
>> Usually when you see a center tapped secondary winding powering a two 
>> diode rectifier you need to watch to see if the center tap also serves as 
>> the ground reference.   I think putting a four diode bridge across the 
>> whole transformer secondary complicates things.... you get about double 
>> the voltage which is not what the loads want.... even if you put a bridge 
>> from center tap to one end of the secondary and another bridge from 
>> center tap to the other end of the secondary, then tied the bridge 
>> outputs together properly you run shorting risks in the bridges when 
>> their diodes have extremely small differences in switching times.... ergo 
>> they'll run hot even in the best case scenario... even if this would seem 
>> to work it seems one risks overheated bridges and also the possiblility 
>> that the wire size in the transformer secondary would not be correct for 
>> the changed current demand.
>> Ron is right, it was engineered for two diodes..... leave good news 
>> alone.
>> Cheers,
>> Don
>>
>>
>> ----- Original Message ----- 
>> From: "Ron" <tracron at bigpond.net.au>
>> To: "Jukebox mailing list" <jukebox-list at lists.netlojix.com>
>> Sent: Tuesday, May 01, 2007 9:13 AM
>> Subject: Re: [Jukebox-list] Selenium Rectifier
>>
>>
>>> The two diode design works well, leave it.
>>> There is no advantage trying to modify it.
>>> May be to high a voltage from the diodes since the selenium rectifier 
>>> has been replaced, just check the voltage.
>>> 30 volts sounds okay I think it should be around 28V .
>>> Ron from OZ
>>> ----- Original Message ----- 
>>> From: "Jim Poe" <jpoe at dsldata.com>
>>> To: "Jukebox mailing list" <jukebox-list at lists.netlojix.com>
>>> Sent: Wednesday, May 02, 2007 1:29 AM
>>> Subject: Re: [Jukebox-list] Selenium Rectifier
>>>
>>>
>>>> When I was working on my AMI G-200, I was going to replace the diodes 
>>>> in the power supply with a bridge.  Got it wired up, & realized I had 
>>>> 60 volts instead of the required 30.  The transformer has center tap 
>>>> that is 30V.  Not being that knowledgeable, I went back to 2 diodes as 
>>>> the original design.  Is there a way to get the bridge to work in that 
>>>> situation, where the transformer has a center tap & each side is 30V? 
>>>> Could I only use 1 side of the transformer?
>>>>
>>>> Thanks
>>>> Jim
>>>
>>>
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