Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tone Junkie on December 19, 2011, 12:35:46 am

Title: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: Tone Junkie on December 19, 2011, 12:35:46 am

Ive tried using the standard method just going off one side and building a marshall type bias circuit but it hasnt worked for me. any insite on how to do it properly.
Thanks Bill

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: kagliostro on December 19, 2011, 02:35:32 am

Quote

Ive tried using the standard method just going off one side and building a marshall type bias circuit but it hasnt worked for me.

Please give other infos

Is this the schematic you followed ?

Kagliostro

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: Tone Junkie on December 19, 2011, 02:40:17 am

No but that one looks like its worth a try.
Thanks Bill

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: kagliostro on December 19, 2011, 03:42:09 am

Look to Sluckey's Amp Scrapbook (the origin of that schematic)

there is also one other way to skin the cat

the Typical Marshall way (right & top of page 5)

http://home.comcast.net/~seluckey/amps/misc/Amp_Scrapbook.pdf (http://home.comcast.net/~seluckey/amps/misc/Amp_Scrapbook.pdf)

Kagliostro

p.s.: Thanks to Sluckey sharing that file

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: stratele52 on December 19, 2011, 05:35:05 am

Quote from: Tone Junkie on December 19, 2011, 02:40:17 am

Ive tried using the standard method just going off one side and building a marshall type bias circuit but it hasnt worked for me. any insite on how to do it properly.
Thanks Bill
No but that one looks like its worth a try.
Thanks Bill

Which Marshall you make and does'nt work ?

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: Tone Junkie on December 20, 2011, 01:32:14 am

Stratele52 I had a transformer that I had to use a full wave bridge because it didnt have HV center tap and when I did the standard marshall take off from one side like they use on the plexi amp it didnt work. I didnt have a marshall I just use that scheme alot.
I was actually making a trainwreck with spare parts I had laying around, i thought what the heck I can get what I needed from that transformer I just didnt do my home work first.
I will implemant one of the 2 ways shown in the morning.
Thanks Bill    

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: eleventeen on December 20, 2011, 01:42:45 am

You have to include the series capacitor if you're going to come off one side of a bridge rectifier. This is done in Bogen amps. You see it a lot more when the main rectifier is a half-wave diode voltage doubler.

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: Tone Junkie on December 20, 2011, 01:48:34 am

Thanks guys I like comming here and asking questions I always learn something good here.
Bill

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: Tone Junkie on December 20, 2011, 01:01:42 pm

Worked perfect guys thanks.
Bill

Title: Re: building a bias circuit from tranformer using full wave bridge and no center tap
Post by: kagliostro on December 20, 2011, 01:10:03 pm

Glad you solved the problem  :smiley:

Kagliostro