Quick Scott 222D question

[BuzzK]

The stock bias bridge rectifier -- looks like silicon. Is it selenium?

THX

 

[seta1]

The stock bias bridge rectifier -- looks like silicon. Is it selenium?

THX

I have yet to see a stock silicon bias rectifier in a Scott tube amp. Normally they are Siemens selenium rectifiers. They don't normally fail completely, but they loose efficiency which translates into lower and lower bias voltages as the things age. They are dirt cheap, just replace the thing with a modern silicon bridge rectifier. Should also replace all the capacitors in the bias circuit as well.

 

[BuzzK]

Thank you.

All of the cans are going to be replaced. In the last Scott 222D that I worked on, the bias can was bad. Surprising to me, since that was the lowest voltage unit.

Unfortunately, with a positive can, means that I'll have to restuff it myself . . .

 

[GreatTone]

Thank you.

All of the cans are going to be replaced. In the last Scott 222D that I worked on, the bias can was bad. Surprising to me, since that was the lowest voltage unit.

Unfortunately, with a positive can, means that I'll have to restuff it myself . . .

On my newly acquired SCA-35, the bias cap was also the first to fail. Since it's a common value and a low voltage cap (100uF/25V), a quick trip to Radio Shack and I was able to tack in a temporary replacement.

 

[audiodon]

BuzzK,

That is a truly beautiful amp. I'll be watching this thread with interest.

 

[Bluelobster]

I have yet to see a stock silicon bias rectifier in a Scott tube amp. Normally they are Siemens selenium rectifiers. They don't normally fail completely, but they loose efficiency which translates into lower and lower bias voltages as the things age. They are dirt cheap, just replace the thing with a modern silicon bridge rectifier. Should also replace all the capacitors in the bias circuit as well.

Use this one. It will fit right where the Siemens rectifier is. You can these at your local store. Actually a 4 amp / 400v is enough but it seems they don't carry them any longer.
http://www.radioshack.com/product/index.jsp?productId=2062583