AB763 Deluxe Reverb (6a20) Build Troubleshooting

That switch unloads the signal going into the phase inverter. You will still have the oscillation with trem pedal engaged so that sounds right. On that switch contact can you ohm to ground and watch it oscilate? Also do you see any light from the neon bulb? You can usually see something.

 

Ok, so v5a is oscillating

Is there oscillation on pin 7 and pin 6 and at the neon bulb connected off pin 6 at the top of the 10M

 

Can you confirm the 10M resistor, I cant really see the color bands. And that the red lead from pin 6 goes to the top of the 10M and not the top of the 100k. If good you should be able to watch voltage oscilate with your leads connected to each leg of the bulb. Red on one leg, black on the other.

Check also the ldr on the other side. Ohm across the legs without light you should have high resistance, I dont recal the value. You will have to disconect either the ground from one leg or the wire off the other leg to the intensity pot at a convenient spot to get a proper reading on the ldr.

 

A good nights rest and a fresh cup of coffee can do wonders!

If I can help at all, it is my pleasure.

 

Are you sure you don't have the bug backwards?

 

Most aftermarket and replacement bugs have a white dot that should be facing the tube side of the amp.

 

The Weber optocouplers have an "N" on the neon side and in the OP's pictures the "N" is oriented correctly HOWEVER (this is a stretch) it might be marked wrong (they are made by humans who make mistakes) - the bulge in the shrink wrap sure looks to me like the resistor is on the side marked "N" rather than the neon bulb.

 

The PT has dual HT taps. (If the Weber site has given the voltages in AC), you are using the 270-0-270. The layout Rob provided shows 330-0-330. If you use the red wires it will give 340-0-340.

Power up!

 

Sure does look that way

G,

Put your ohm meter on the legs of the roach and shine a light into the end. If the resistance drops you have the ldr end. Check both sides.

 

Very nice work D'tar.

 

Power up indeed!!!

 

That could be quite versatile PT eh!

 

That's a great PT.

 

You think so too!

Just watch the filter cap voltages.

 

By cap can I meant doghouse. Yours has a cap can like a Princeton?

The red dot on the opti goes on the tube socket side according to my notes.

I have had Fender tremelos not work for some reason, then suddenly they will start after playing a while, or the next time you turn the amp on. I always assumed it was something to do with a failing roach or the particular tube in the tremelo tube driver position.

 

I built a 6a20 a few years ago, I put a Weber 15F150 speaker in it (I had Peavey Delta Blues envy at the time) and it is still my favorite amp, fantastic tone. As I recall I had an issue with the optocoupler being marked incorrectly.