Ok, stumped DRRI conversion to AB763

[WillieBoy]

I have been staring at the schematics for 20 minutes, and I am just stumped.  Has anyone done a conversion of a DRRI to a Hoffman AB763?  I keep looking at the node coming off of the Fender schematic, I have a brown, a yellow and an orange wire.

In the Fender schematic

Brown wire  goes to pin 6 of V1, V2 and V4

Yellow wire goes to pin 6 of V6 (inverter)

Orange wire red wire on the reverb transformer

On the Hoffman AB763 going from lower right to left on the layout standby switch:

2-22uF caps then the choke then another 22uF cap then a node that goes to a 470 ohm resistor to pin 4 of V8

Next node over 470 Ohm resistor which goes to pin 4 of V7/Pin 6 of V5 and and the red wire on the Reverb Choke

Through a 1K Ohm resistor

Next node another 22uF cap/100K Ohm resistor that goes to pin 6 on V6 and Pin 6 V8

Next node 82K resistor goes to Pin 1 V6 V4

Question

Through a 4.7K resistor

Next node 22Uf Cap to 100K resitor to Pin 6

All that said, I think I see where the Orange wire goes (Red wire on Reverb Choke)-The rest just is confusing me.  Anyone have a gut shot of a conversion or something?

[phsyconoodler]

What kind of conversion are you attempting here?Hand wired or a PC board modification?
  I've done lots of hand-wired conversions but none to Hoffman specs,all to original AB763 specs.

[WillieBoy]

Taking a DRRI and removing the circuit board (I toasted it fooling around with it). 

Then putting in a Hoffman AB763.

 I can follow most of the schematic, but the PT section is just throwing me for a loop.  I could just take leads off of the PT and rewire the lot of it onto the board like the Hoffman AB763 shows in the diagram, but, being kind of lazy and not wanting to redo functioning work, I'd like to just take the leads that already have the caps wired in and putting them onto the correct nodes onto the Hoffman board.

[eleventeen]

Unless I'm misunderstanding, you may be obsessing over (nothing more than) mere wire colors here...Obviously, if you drop a functioning AB763 board into a DRRI, you have every part, in terms of tubes and sockets and pots and jacks and switches and trannies, and they are all in exactly the same spot as they would be in an original AB763 Deluxe, on the same size chassis. The only issues (and I don't know the answers because I haven't done such a "conversion") I can imagine would be:

Are the grid stopper (if any) resistors and the screen resistors there? both mounted on the 6V6 tube sockets. 

Is the grounding scheme coherent, eg; does everything that needs a ground have a good way to get to good audio
ground?

Is there a provision for a heater center tap connection to ground; either by actual heater winding CT or by synthetic dual-100 ohm resistors...and where (if resistors) are those to be located?

As for the electrolytics, I myself wouldn't rely solely on wire insulation color as being the same/consistent from 1965 to 2005. Just woundn't do that.

None of these things is at all difficult, but IMO you have to "own" them a little more; meaning study and confirm that the wires you're going to re-use from the "old" amp go where you want; instead of just saying "...orange = orange and yellow = yellow, so I'm good to go".

[sluckey]

Orange wire red wire on the reverb transformer

It feeds a lot more than that! It also feeds the output tube screens and V5 trem tube.

This should help with the confusion... http://home.comcast.net/~seluckey/amps/misc/Hoffman_AB763.pdf

Node B is your orange wire.
Node C is your yellow wire.
Node D is your brown wire.

I suggest you forget about the DRRI schematic and just wire it according to Hoffman's layout. And build a new cap board while you're at it. There are a couple things you should know about the power supply. Hoffman shows 1K and 4.7K dropping resistors between nodes B, C, and D. These are correct for most AB763 circuits, but not for the DR. The DR uses two 10Ks. Also, your DRRI uses a 220µF and 47µF connected in series for the node A cap, but the DR AB763 uses two paralleled 22µF caps.

Lot of pics here... http://deluxereverb.waynereno.com/

[WillieBoy]

Thanks Sluckey!  I was hoping you were going to chime in! 

Ok, looks like I build a new board?   and lose the 1K and 4.7K dropping resistors, replace with 10Ks, and buy 5 22uF caps and put them in.  One other question.  Based on what you know, does it look like I might have to change the bias resistor too?  Thanks for passing the Hoffman schematic along, much easier now!

[P Batty]

You could check out Wayne Reno's site:

http://deluxereverb.waynereno.com/

It shows the steps he took in his DRRI conversion- there are good pictures, especially of a new cap board.  It's a little different than a Hoffman board, but it shows, in a step-by-step manner, the choices you have to make when doing a rebuild.  Only start rewiring when you have a good idea of what you intend to accomplish. Get the power and heater supplies figured out first.  Take your time.

UPDATE: You've got two threads going, I didn't see that you have looked at that site already. 

[sluckey]

does it look like I might have to change the bias resistor too?

Maybe. I used a 470Ω/1W, 10K pot, and 10K just like the original.

[WillieBoy]

I did look at Wayne's site (oddly enough, my name is Wayne, also.  I saw that he rebuilt the board, I was hoping I didn't have to.  The power supply really has tripped me up, the rest of the schematic between the DRRI and the Hoffman AB763 is pretty much the same, or at least close enough that it is pretty easy to follow.  I saw the 100 Ohm resistors in the heater section you referred to. 

I probably should have tried an easier amp to start, but it is pretty common of me to go with something a bit more complex and learn by blowing stuff up.

Here is a copy of the DRRI schematic, for reference.

[P Batty]

I rebuilt a Silver-faced Deluxe Reverb into a blackface, using a Hoffman board, this forum and a bunch of internet references.  I also used Dan Torres Inside Tube Amps book.  I don't think much of his tone mods, but the section on building a power supply and bias supply was pretty good, the Bias charts are handy when trying different tubes.  Definitely use the 1Ω resistors- They make setting and adjusting the bias a science, rather than an art.

[sluckey]

Here's a much nicer schematic... http://www.el34world.com/charts/Schematics/files/fender/65_deluxe_reverb_manual.pdf

You really should forget this schematic and get familiar with the Hoffman layout/schematic. It would be useful to study the original DR AB763 schematic but everything you need is in the Hoffman pdf.

I would definitely replace the cap board. It's very easy. Here's mine...  http://home.comcast.net/~seluckey/amps/tdr/tdr.pdf

Duh! I'm not thinking. You don't necessarily need a cap board. Hoffman's board can accommodate the filter caps.