Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on November 27, 2013, 01:34:51 pm

Title: PT Hammond 291AEX is adequate for a Princeton Reverb ?
Post by: kagliostro on November 27, 2013, 01:34:51 pm

The Hammond 291AEX is sold as adequate for some Fender amps

https://www.tube-town.net/ttstore/product_info.php/info/p3346_Hammond-291AEX-Fender-Power-125P1B---022772-UPGRADE-Champ.html (https://www.tube-town.net/ttstore/product_info.php/info/p3346_Hammond-291AEX-Fender-Power-125P1B---022772-UPGRADE-Champ.html)

Champ, Vibro Champ, Princeton, Princeton Reverb, Tweed Deluxe

the datasheet say 650V CT 81mA - 6.3V 2A - 5V 2A

http://www.hammondmfg.com/pdf/EDB291AEX.pdf (http://www.hammondmfg.com/pdf/EDB291AEX.pdf)

the question is about the 81mA B+

but in the net can be find indications for the use of a 100mA and also 200mA PT

May I consider the 291AEX adequate for a Princeton Reverb ?

Thanks

K

Title: Re: PT Hammond 291AEX is adequate for a Princeton Reverb ?
Post by: Willabe on November 27, 2013, 03:33:07 pm

Good question.

Doug's PT for a Princeton/Champ is listed as 70mA. His PT for a Deluxe Reverb is listed as 120mA

Mojo says their PT for BF P and Champ is 75mA,

http://www.mojotone.com/amp-parts/amp-transformers-fender-power/Tweed-Blackface-Princeton-Champ-Power-Transformer-EX (http://www.mojotone.com/amp-parts/amp-transformers-fender-power/Tweed-Blackface-Princeton-Champ-Power-Transformer-EX)

My BF PR PT is stamped 125P1B, the tube chart in the amp says AA764 for the model # and shows a GZ34 for the rectifier.

From a Gerald Webber book, Fender Transformer cross references;

Champ AA764, PT, 125P1B

Deluxe/Reverb AA763, PT, 125P23B

Harvard 6G10, PT, 125P1A

Princeton AA1164, PT, 125P1B

All the other amps that have or don't have reverb are listed like this; Deluxe/Reverb except for the Princeton.   :dontknow: 


             Brad     :icon_biggrin:

Title: Re: PT Hammond 291AEX is adequate for a Princeton Reverb ?
Post by: jjasilli on November 27, 2013, 04:01:05 pm

Tube data sheets are the place to look; see:  http://www.mif.pg.gda.pl/homepages/frank/sheets/135/6/6V6GTA.pdf (http://www.mif.pg.gda.pl/homepages/frank/sheets/135/6/6V6GTA.pdf)

At max signal condition, in Class AB, 2X PP 6V6's draw 90mA.  But the amp is not always in max signal condition, and Hammond trannies are considered "over" rated in terms of power handling capacity by as much 50%.  So a 70mA PT from a quality manufacturer is considered standard for a 2X PP 6V6 amp.  The current draw of the preamp & PI tubes is too small to be considered.

Also, for guitar amps it is considered good for components to be operating "on the edge".  For hi-fi, maybe not.  A 70mA tranny is a fine choice.  The only way to know if you would prefer bigger trannies is to A/B them.

I hotrodded my Princeton (since sold) to use 6L6's, which have more current draw, and more heater draw too.  The PT git real hot so I installed a fan.  

Title: Re: PT Hammond 291AEX is adequate for a Princeton Reverb ?
Post by: kagliostro on November 28, 2013, 12:47:11 am

Many Thanks Jjasilli

for sharing your experience, it is best of any consideration that can be done  :thumbsup:

K