Mark IIB-help with lead Drive pot connections to RP-9A board

[McBarry]

Hi folks,
long story short, I want to rid my baby of a reverb mod - looks like someone wanted to add more reverb to the lead channel via a pot on rear chassis.

I need to know for the lead drive pot to RP-9A pramp board..
top lug goes (eventually) to earth. Fair enough.
middle goes directly to V3 pin7. Fair enough.
BOTTOM LUG: currently mine goes to a 470k then to a .047 orange drop to V2pin6 (very different from schematic, but looks very factory original).
There is a join before the 470k resistor - I'm wondering if a cap like the one shown in the schematic has been removed??
Also wondering if the 470k is indeed correct??

In this pic, the red wire before the 470k goes to the "new" reverb pot and the white wire is the return - both are going to be removed..

Given these amps rarely follow the diagram(s), could I bother someone/folks to please, please have a squizz inside theirs and let me know what gives??
I'd be ever so grateful!!
Regs, Dave

 

[McBarry]

Nobody able to help out ??

I'm thinking these preamp boards may be in the Mark IIA also - I'm going to look inside mind tomorrow morning..
DB

 

[McBarry]

For future ref, my Mk IIA has an RP-6 board, and it seems the various schematic floating around the globe are pertinent to the different boards.
Now why didn't I think of that before...

 

[TiPiMods]

Maybe this helps, took this foto yesterday when I modded my master volume 1 so I know how it was original:

the pot on the right is master 1, on the left is lead master, in the middle is lead drive. Looks like there is some resistor and capacitor missing on your picture. On the schematic its 33k and .005 on the gain boost switch. I dont see what it has to do with the reverb.
hope it helps a bit.
Btw: mine is a RP 9A board

 

[McBarry]

Well, to be precise, you have a beautifully clean and neat looking RP-9A board TPI..LOL
(I'm guessing you've cleaned it as I can't see much resin around the joints..)

On your lead drive pot, the top lug goes to ground.
Does the second lug accept the 33K from PCB and the cap to earth ?
Also where does the grey wire to V3pin7 connect to - the same lug or to the bottom lug ?
Cheers, Dave

 

[TiPiMods]

Didn't do anything with my board, I bought it like that. The Amp must have been in the living room more than on stages before I bought it. This will probably change now :lol:

I'm sorry, I dont have the amp open now, but what I can see on the schematic it should be like that: drive pot: grey cable is middle lug and goes to grid of V3, top lug is ground, lug on bottom recieves the rev mix resistors. Look on the schematic of the Mk IIA, its a little different from IIB.
I'll make a better foto next time I have the amp opened.