Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Apexelectric on February 25, 2018, 09:49:16 am

Title: AO-29 Percussion transformers
Post by: Apexelectric on February 25, 2018, 09:49:16 am

I have a couple Hammond AO-29 amps that I was going to part out and wondered if anyone has found a good use for T4, T5 and T6 in the M-3 schematic, T3 and T7 will be useful as th OT and PT for another build. They appear to be part of the percussion section of the amp. Do any of these make good reverb/output transformers?

Title: Re: AO-29 Percussion transformers
Post by: sluckey on February 25, 2018, 10:10:48 am

I don't think they would be useful in any guitar amp circuits I'm familiar with.

Title: Re: AO-29 Percussion transformers
Post by: Apexelectric on February 25, 2018, 10:27:58 am

Are they serving the purpose of an impedance matching output transformer in the circuit? Would it be worthwhile to find out the turns ratio and see if they could be repurposed?

Title: Re: AO-29 Percussion transformers
Post by: sluckey on February 25, 2018, 08:45:52 pm

Probably more involved than that. I quit looking as soon as I realized they are not useful to any guitar amp circuits I'm familiar with. Why don't you search for a service manual. Many times they will include a theory of operation section. A good starting place would be captain foldback's website.

Title: Re: AO-29 Percussion transformers
Post by: PRR on February 25, 2018, 09:05:14 pm

It's a classic 2-stage push-pull (low)power amplifier.

However the input winding seems to be super low impedance; the output winding a super high impedance.

The interstage may be OK for a similar task. (Which we mostly don't do in guitar amps.)

However what is the frequency range of the Percussion signals? May be far less than full audio(/guitar) band.