Anyone successful in doing the Dumble-like AB763 Fender Mods

[moonbirdmusic]

Hello all -

I am referring to the 3-phase, Dumble-like mods for the "normal channel" on Fender AB763 based amps as shown here:

http://schematicheaven.com/dumble.htm

I have tried doing these mods and I could not get the FULLY updated Normal channel (thru mod #3) to output ANYTHING. Has anyone ever tried these mods and "lived" to tell about it?? I know its highly likely I just blew it -- but thought I would ask first before I started over.

BTW - I did all the mods at once (very dumb I know now) before any testing. So I am not asking for specific troubleshooting (yet) - but more just an overall sanity check. (The attached file is mod #3 which I did).

If you have done it - I would really like to hear what you think of the mods and anything that I might do different.

thx.

[M Fowler]

No but one is a P-P pot so the switch should be good there but the other switch is that on-on-on?

[Rob Livesey]

I did them on a SF Pro Reverb many years ago. I added a mid pot on the back panel, they did work and sounded pretty good. At least I had the option of something different on the normal channel. I also added a pot to reduce the negative feedback

If I remember right, the channel would drive quite nicely with PAB engaged and the negative feedback turned down. It wasn't full on overdrive, but it was usable.

Rob.

[dobbhill]

I did the simple one without switches: kept the bright switch. I put the mid pot in the #2 input hole (I do that to a lot of Fenders). Mine was a SF Super Reverb. Added another option for tone. Really worked well with Tube Screamer. The new owner of the amp really liked it to.
D