Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: John on June 10, 2012, 09:03:58 am

Title: PT idea, suggestion, question
Post by: John on June 10, 2012, 09:03:58 am

A lot of the topics I read have to do with B+ being too high. That's my common peeve as well. So, question first - is it possible for a transformer to put out 120 -150 mA while only having say, a 250-0-250 winding?

If it is, I wonder if Doug could stock em?  :grin:

I know you can always lower the B+ through resistors, tube rect. etc, I'm just wishing for a simple solution. Should I get 2 hats?  :laugh:

 I'm sure a lot of guys are like me, with the wall voltage being well over 120. Mine usually runs 125-127, so even a 290-0-290 ends up putting out ~430 VDC, sometimes more.

Title: Re: PT idea, suggestion, question
Post by: PRR on June 10, 2012, 10:12:46 pm

230V transformers are easy to find from 50mA to 20,000mA.

Problem is finding one with a 6V winding also.

Title: Re: PT idea, suggestion, question
Post by: stratele52 on June 11, 2012, 03:37:14 am

Quote from: John on June 10, 2012, 09:03:58 am

I know you can always lower the B+ through resistors, tube rect. etc, I'm just wishing for a simple solution. 
 

Resistor ; give you too much sag , tube rectifier; not enough choice

Very easy way ; some 10 volts 5 watts zener diodes like 1N5347B  less than $1 us each

On any kind of project you could need them. Also when fixing old amp working on 110 volts AC wall outlets, sometimes I use zener diode to lower B+, today wall outlet could give more than 120 AC

Title: Re: PT idea, suggestion, question
Post by: stratele52 on June 11, 2012, 03:58:22 pm

Quote from: drgonzonm on June 11, 2012, 02:35:45 pm

     ..... black boxes you can put between your amp and the plug to selectively reduce voltage

.

Not good choice . You must not reduce heater voltage , only B+