Which is the ref of this OT transformer?help

General discussion area for tube amps.

Moderators: pompeiisneaks, Colossal

Post Reply
boops
Posts: 25
Joined: Sun Oct 16, 2016 8:23 pm
Location: France

Which is the ref of this OT transformer?help

Post by boops »

Hi
Is someone knows the ref (the primary impedance) of this transformer OT 3 output 4/8/16 ohms,installed in a 60 \70 ‘s guyatone tube amp ,it’s seems it’s not the original one , circuit close to an AB 763,I found it with some el34 and at max a very low bias .Many thanks .


https://www.noelshack.com/2018-03-6-151 ... 75ff7.jpeg#
https://www.noelshack.com/2018-03-6-151 ... c266c.jpeg#
Stevem
Posts: 4551
Joined: Fri Jan 24, 2014 3:01 pm
Location: 1/3rd the way out one of the arms of the Milkyway.

Re: Which is the ref of this OT transformer?help

Post by Stevem »

Are you having problems with the amp having low output?
The only way to find out what the primary impedence is is to pump alow amount of AC voltage into it .
Do a web search for testing a OT that way.

In general from what I have seen when you run 6L6 type tubes on a OT made / wound for 34s you get 30% less output power then you should have , and bias wise 6l6 type tubes may need as high as -48 volts of bias where as 34s can fly with atleast 8 volts less,and of course with either tube this hinges on the plate and screen voltage .
Always keep in mind that the level of screen voltage in large part determines the bias needs of the tubes used!

Should you have a shorted OT then when you drive the amp with signal you will see the current go up as expected / as normal, but you will hear very little output from the speaker.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
User avatar
Phil_S
Posts: 5936
Joined: Tue Oct 23, 2007 10:12 pm
Location: Baltimore, MD

Re: Which is the ref of this OT transformer?help

Post by Phil_S »

What Steven says. Here.
Determining Output Transformer Impedance: http://www.radioremembered.org/outimp.htm
Post Reply