AB763 Board kit - Reverb and Trem problems

[derekiseric]

Hi all, I’m new here. 

I did read all the information before posting but I’m still having some trouble with my
Hoffman Deluxe Reverb board kit install on my Fender 64 Handwired Deluxe Reverb.  The fender layout was very noisy and since changing the board is much more quiet, that’s good news.

The amp works great and sounds awesome when just playing but it seems since I swapped out the handwired Fender board for the Hoffman board the Reverb now seems to feedback on itself when you turn it past 3 on the dial and the trem doesn’t seem to turn on at all with the footswitch (I’ve tried two).   

I measured V3, V4, and V5.  I took some pictures but I can’t get them to attach to the post.  I’m new at this so any help would be awesome.

Here’s what I’ve got:
V3

Pin:
1 - 404v
2 - 137.3mv
3 - 21.52v
4 - 3.3ac



V4

1 - 199.7
2 - 2.5mv
3 - 1.59v
4 & 5 - 3.3ac
6 - 198.2v
7 - 50mv
8 - 1.6v
9 - 1.59ac


V5
1 - 198.7
2 - 39mv
3 - 2.1v
4 & 5 - 3.3ac
6 - 416.9v
7 - 198.7
8 - 206v

[sluckey]

Check your wiring and verify correct component values. Unlike a real AB763 circuit, the Hoffman circuit does not require a footswitch for tremolo to work.

[derekiseric]

Thank you for the response Sluckey.

So I’ve checked all of my wiring 3x over - and the wiring and parts are in the correct places.

I got the tremolo to work by disconnecting the wire going to the footswitch jack.  I don’t use the footswitch anyway.  I’d rather have everything controlled by the dials.

Now for the Reverb - I put a type 2 Trainwreck style PPIV MV just to see if the Reverb feedback would stop at lower volumes and it does.  When I turn down the master volume I can turn the Reverb to 10 and it’s fine.  But when the MV is set to 10 and I turn the vibrato channel volume to 2 the Reverb feedsback on itself if I turn the Reverb past 3. 

Right now the amp is out of the cab and the Reverb tank is inside the cab. 

Any ideas?

[sluckey]

I got the tremolo to work by disconnecting the wire going to the footswitch jack.

The FS jack must be grounding that wire somehow. Check the jack wiring. If using an RCA phono jack be sure the tip does not touch the shell. If using a 1/4" phone jack be sure the wire is connected to the tip lug only and not the ground or switch lug.

The reverb circuit can be finicky, especially when the amp is spread out on a bench. Placement of the tank is also a factor. You are using shielded cables right?

[derekiseric]

The footswitch jack was grounding out so I just removed it because I don’t like to have to use it.

I opened up the Reverb tank and re inserted the RCA plugs back into it and screwed it back down to the cab.  It seems to be working now.  That’s a huge relief!  And yes, shielded wire on the input jacks and volume pots as well as the Reverb cables to the tank.

The tremolo on the Hoffman layout is amazing!


Thank you so much for your help Sluckey! I appreciate the time and advice!