Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on February 19, 2013, 04:06:22 am

Title: Twin Reverb 135 MV pot substitutes ?
Post by: kagliostro on February 19, 2013, 04:06:22 am

Which is the right substitute for the MV pot on the Twin Reverb 135 ?

it is a pot with physiological intake  :help:

(http://www.diyitalia.eu/forum/download/file.php?id=7888)

http://www.el34world.com/charts/Schematics/files/fender/twin_reverb_sf_135_schem.pdf (http://www.el34world.com/charts/Schematics/files/fender/twin_reverb_sf_135_schem.pdf)

EDIT: I've find an 1MLog PP DPDT pot, but as you can read there isn't the physiological intake
http://www.tubeampdoctor.com/product_info.php?language=en&category_id=126&products_id=29&mySID=WYGJVXa9Ao28FB7jybrwo3 (http://www.tubeampdoctor.com/product_info.php?language=en&category_id=126&products_id=29&mySID=WYGJVXa9Ao28FB7jybrwo3)

K

Title: Re: Twin Reverb 135 MV pot substitutes ?
Post by: sluckey on February 19, 2013, 07:31:04 am

That pot may be very hard to find. I would use the 1M LOG with pp switch and connect the 120pF as a standard bright cap, ie, between left lug and wiper.

If you have the old pot you can probably measure the resistance from the ends of the pot to the tap but the chances of actually finding a pot with the same tap AND a pp switch are slim.

Title: Re: Twin Reverb 135 MV pot substitutes ?
Post by: kagliostro on February 19, 2013, 10:07:00 am

Thanks Steve

If there wasn't the PP switch I think a rotary switch with resistors and an intake between it  can do the job

but I don't know rotary switch with PP function

So, as you suggest, a cap connected as a standard bright cap will be the solution

Franco