’65 Deluxe Reverb Reissue rewire

Posted by on May 11, 2013 in Amp Repair, Electronics Repair, General, Home, News | 0 comments

This project will be to remove the printed circuit boards from my ’65 Fender Deluxe Reverb Amp (made in 2010) and replace them with real, old style point to point wiring with beefier quality components. I will wire this to be an exact Fender AB763 circuit. Notice the small, inexpensive components, ribbon cables, push on connectors, and thin wires going to the tube sockets. It is all done to keep costs down. Not only do these modern manufacturing practices not sound as good as hand wired point to point, they are not as reliable. Here is the very beginning of the deconstruction. The knobs are off, pots and jacks unscrewed, ribbon cables disconnected, and front panel assy. ready to be removed.

'65 Deluxe Reverb PCBs

’65 Deluxe Reverb PCBs 

 

 

Next we have the chassis free from the mass produced computer designed circuit boards, ready to be prepped for the new installation. I will carefully remove all solder and wire from the tube socket pins, and clip off all the push on connectors on the wires from the transformers and power supply. I will keep the transformers, tube sockets, switches, fuse holder, lamp, power cord, bias pot, speaker jacks, and filter supply board. Pretty much everything else is getting replaced.

'65 Deluxe Reverb with chassis gutted

’65 Deluxe Reverb with chassis gutted

 

 

Today I wired up everything I could until the parts are delivered.  First was the line power cord, switch, fuse and power transformer, all carefully routed and tucked away next to the chassis for minimal noise and clutter.  This power switch switches both hot and neutral line feeds, which is good if the outlet you are plugged into is reversed for some reason, so I kept it.  Notice the two resistors I soldered to the chassis on the white ceramic tube sockets. These are 1 ohm resistors that are for easy bias measurement, and have no effect on sound or performance. Also notice the two resistors at lower right coming off the pilot lamp. The 6.3 v filament winding goes to the pilot lamp first, before it heads off to heat each tube. These resistors reference the supply voltage to ground, keeping it balanced and helping to reduce hum in the circuit.

65 Deluxe Reverb rewired power section

65 Deluxe Reverb rewired power section

 

 

This is what wiring I could do to the other end of the chassis. The reverb in/out jacks were a function of the main board on the re-issue, and came down through the bottom plane of the chassis. You can see the two jack holes and screw mounting hole for the plastic assembly. I relocated them to the traditional back panel with old style metal jacks, and wired them up. I also wired up most of the reverb transformer. The 2 conductor jack to the right is the new style jack that works with the rev/trem foot switch that came with the amp. I am keeping that also.

65 Deluxe Reverb reverb/trem

65 Deluxe Reverb reverb/trem

 

 

New CTS brass shaft control pots installed. Since the new pots are a bit larger I had to drill out and de-burr all the mounting holes.

New brass shaft CTS pots

New brass shaft CTS pots

 

Here is the bias rectifier board built and installed. The red wire is a winding from the power transformer that supplies an AC voltage to be rectified by the resistor, diode and capacitor and fed via the yellow wire to the bias adjustment pot. From there the negative DC voltage is sent to the grids of both output tubes so that the bias point of those tubes may be set.

AB763 bias rectifier board

AB763 bias rectifier board

 

 

Now I am nearing the finish line. Most of the main board is wired. I still need to wire up the filament twisted pairs that supply the power to the tube heaters. And I need to wire up the pre-amp side of the grounding scheme, as well as pop in a few missing resistors. I sincerely hope I don’t have to get under this board for some reason, because it would mean a back breaking amount of un-soldering and re-soldering. So I am taking my time and double checking everything.

65 Deluxe Reverb about to hatch

65 Deluxe Reverb about to hatch

 

Well, a set back. Once the board was all wired up, the amp worked, but it had scratchy pots and a little bit of hum. After painstakingly searching and testing I determined that the black fiber board that I had soldered everything to was actually absorbing moisture from the air and conducting, causing dc voltage leakages in different parts of the circuits. I could measure voltages right on the board material itself and on eyelets with nothing in them. In fact, after heating an eyelet with my soldering iron for a bit, the voltages went away, but returned to a lesser extent one rainy day later, and back to full two days later.

I can’t be happy with that situation, so unfortunately it means tearing out the fiber board and starting anew with a different material. I can’t express just how disappointed I am with this. This time I will use a material called Garolite G-10, a phenolic glass board, and will use turrets instead of eyelets. Some of the components I can reuse, but the solder/unsolder/re-solder would be too much damage from heat for me to feel comfortable using many of them in the new build. Stay tuned.

 

It’s now about two months later, and the new turret board re-wire is nearly completed. The main board is all wired up, but the small bais supply board was a bit too large, and had to be cut down to size in order to fit in the space above the power transformer.  I have three builds going at the moment, but I hope to get it fired up and into testing within the week. Here is a shot of the new re-wire.

'65 DRRI turret board re-wire

’65 DRRI turret board re-wire

Success! The amp is finished, and I am happy to say worked perfectly on the first power on. It sounds fantastic. When it was a re-issue it had an issue with the treble content having a tendency to be too ice picky. I had to keep an eye on the treble tone control. But, there is none of that now. It sounds much more warm and fully balanced, with more of a 3 dimensional quality. It’s quiet as a mouse, too. With both volumes all the way up, it is just barely audible with no cord plugged in. It measures just over 19 watts at 400 Hz and just under 21 watts at 1,000 Hz. This was a long and hard fought victory, and I couldn’t be happier with the results. Here it is as finished with a Mercury Magnetics output transformer and original Jensen 100 watt ceramic speaker, which to my ears sounds very good in this amp.

Finished rewired '65 Deluxe Reverb

Finished rewired ’65 Deluxe Reverb

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