1969 Fender Deluxe Reverb Restoration


Introduction

In Fall 2008, I had occasion to work on a friend's 1969 Fender Deluxe Reverb amplifier. Since this was not my amplifier, only necessary repairs and parts replacement was performed. This amp was a post-CBS Fender DR, but apart from a few different components such as the power transformer and rectifier tube, the circuit and tone was surprisingly similar to the pre-CBS DRs I have worked on and listened to.

During physical examination and testing, I found the following problems:

  1. A 14 amp fuse was in in the fuse socket and the spring was missing! Tin foil was used to make the contact to the fuse holder cap. See the photo to the right. This was scary!
  2. A 14 foot (blue) AC power cord which was missing the wall grounding prong had been wired to the power transformer
  3. The power cord grounding wire was disconnected from the chassis inside the amp
  4. A number of bolts and potentiometer mounting nuts were loose or missing
  5. There was loud hum.
  6. The gain was low; it appeared that the tubes may have been original issue. Some of the 12AX7s were noisy
  7. The reverb did not work
  8. The Normal Channel tone stack was extremely noisy
  9. Most of the pots were scratchy/noisy when turned
  10. The power on indicator lamp was burned out

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This amp was a favorite resting spot for our cat. It was obvious that this amp had been roughly handled over time. The first thing I fixed was to put in a 1 amp slow-blow fuse and a new spring-loaded fuse cap. Next I pulled the reverb out of the cabinet and opened it up.

It was easy to see why the reverb did not work. The wires which connect the reverb tank input jack to the input transformer were not connected. It was obvious that this repair had been performed before. Worse yet - the person had used some bad solder such as acid-core and the transformer lugs were corroded and badly damaged. I removed the this bad solder and re-soldered the wires using rosin-core solder. Soldering the connecting wires to the small 30-32 gauge transformer wires was not fun.

The chassis is pulled out of the wood. The "infamous" long blue AC power cord can easily be seen. It had been grounded by placing the grounding wire under one of the power transformer bolts. Unfortunately this bolt had become loose. The AC power cord was replaced and a lug was bolted to chassis and the AC power cord ground wire soldered to this lug. All bolts and nuts were tightened on the chassis.  A new "power on" light bulb was installed.

The stock Jensen 12 inch speaker was in good condition. The reverb tank connection wires seen to the right of the cabinet also tested satisfactory.

Here is the chassis laid out with the cover off of the main filter capacitor bank. The tubes had a thick film on them. This DR really had that "musty old amp" smell when I first turned it on.

Five 16 uF/450 VDC,  paper-covered Mallory electrolytic caps are seen. I believe these were the original filter caps. Other repairs were made - there was a cold solder joint on the Normal Channel tone stack along with evidence of a previous (sloppy looking) repair. Additionally there was AC voltage on the treble pot. This was corrected. The potentiometers were "exercised" by turning them back and forth repeatedly. I also soldered in a new 100 uF/100 VDC bias filter capacitor.

I replaced the tired, old Mallory filter capacitors with some F & T 22 uF/500 volt axial capacitors. This pretty much removed the hum from the audio chain. The old caps can be seen lying on the chassis for size comparison.

I replaced all but 1 tube with mostly NOS tubes and set the bias on the new matched 6V6 pair. I found that by turning the amp on it side it was possible to connect up the reverb patch cords and the speaker for audio testing.

The repaired and tested chassis is laid on top the cabinet prior to reassembly. Note the shiny new tubes. The rectifier is a Russian-made 5U4GB.

Another view of the nearly completed project. The DR was reassembled, final tested and returned to its happy owner.


An original 6V6 tube from this amp is shown above. The original tubes left a grimy, stinky substance on my fingers.


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