Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Oddvar on August 27, 2016, 01:11:35 pm

Title: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: Oddvar on August 27, 2016, 01:11:35 pm

Hi.  A couple of questions:

I have the Pro Junior converted to 18 w Marshall, but the PT has only two primarys outs, seems to be the heater and the boardconnection.  I need the 5 vac to run the 5y3.  Do I need a new PT or is there a way around it?

Question 2:  The pilotlamp is nor connected to the heater circuit, but on the ac itself, is that ok?

I am using the Hoffman layout. 

Title: Re: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: pompeiisneaks on August 27, 2016, 01:18:15 pm

Yes you'd need a separate transformer either that has a 5V tap or a separate 5v transformer, or you could just use diode rectification.  If the pilot lamp is a 120V ac lamp, then yes that is okay.  If that was how it was before, it is fine.

~Phil

Title: Re: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: sluckey on August 27, 2016, 01:29:01 pm

In addition to what pompeiisneaks said, you could use an EZ81 rectifier like the original Marshall 18 watt amp. The EZ81 runs on the 6.3v winding just like your other tubes.

Most of my pilot lamps work from the mains voltage. I prefer that to putting a lamp on the filament circuit.

Title: Re: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: Oddvar on August 27, 2016, 01:35:12 pm

I am in Europe, and what kind of filament transformer would you suggest to run a 5y3GT rectifier? 

Title: Re: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: sluckey on August 27, 2016, 01:54:44 pm

https://www.hammfg.com/files/parts/pdf/266M5.pdf (https://www.hammfg.com/files/parts/pdf/266M5.pdf)

Title: Re: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: Oddvar on August 28, 2016, 04:39:45 am

I might change the PT.  Would this be ok, or is it too  much?

Title: Re: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: sluckey on August 28, 2016, 05:17:03 am

Hoffman sells a fine 18 watt power transformer. And he also has a fine output transformer.

Title: Re: Transformer Pro junior to 18 Watt Marshall (Stout)
Post by: drew on August 28, 2016, 02:13:38 pm

Diodes are cheaper than transformers.  Just sayin'.