Design/Troubleshooting help for new, simpler ReVibe unit

[PassoGavia]

Hi all. Several years ago I almost pulled the trigger on the Weber/Gehring ReVibe harmonic tremolo / reverb unit kit but couldn't get past the price. Along the way, I came across this website:
http://laird.vectorstar.com/music/effects/lesverb
where a guy named Laird Bedore had described his experience building, then improving, the Revibe, and in the process hatching on an idea to get almost the same effect for far fewer parts. I decided to give that a try, and bought all the parts about 4 years ago, but never got around the building it. At that time, I had some nice back and forth emails with Laird, who had designed it but never actually gotten around to building one, either!

Well, I finally did, last month, and it doesn't (yet) work. In those intervening years between buying parts and building, Laird unfortunately passed away. So here I am, trying to figure out whether his design is genius, or not. I'm an optimist!

I'll post some photos of my project later tonight, but in the interim the schematic and layout drawings he made are attached. Right off the bat, I think the 470-ohm resistor on the filter caps in the power supply is too low rated (he spec'd 1/2 watt but I'm sure mine blew on the first power-up and my calcs tell me it should have been much higher rated than that) and superfluous (I am getting a max of ~160V DC on those caps which seems appropriate for the circuit, so I'm not sure why a stepping down of voltage is even required for B+).

The reverb driver and recovery sections seem to be working fine, but I get no actual reverb out of the tank. I'm using a 9FB2A1C tank instead of what he spec'd, but that shouldn't matter, should it? The high input impedance of the "F" models seemed to be what he felt was needed given the lack of a transformer for the reverb tank input - mine just has longer springs, difference mounting orientation, and jacks than the 8FB2C1B called for.

On the tremolo side, I am getting something resembling the low-frequency tremolo but not yet the high-frequency side. I need to check some connections there.

Anyway, I'd really appreciate some assistance with the design in general (will this actually ever work? could it be improved?) as well as my troubleshooting. I've built tube amps and other mains-powered guitar circuits before, and effects pedals for decades but I'm a novice with sorting out tube circuits themselves, especially for an effect like this.

Thanks!

[PassoGavia]

Attached are some photos of the project.

20190114_202512.jpg

20190114_202404.jpg

[sluckey]

Interesting idea! I hope you get it working and will share your opinion about this circuit.

[Greyrocker]

Hello all,
I a new to this forum. I have been building sound effect circuits for many years. Some work well, others no so well. I found Laird's site about a year ago while researching uses for the 12FQ8 tube and have wanted to build the tremolo section. I noticed there is a what may be a flaw in Laird's schematic when comparing it to his layout. In the schematic the 3M reverse audio pots have all 3 lugs connected, but in the layout only 2 are connected. Sluckey have you tried disconnecting those lugs as per the layout? Maybe this is why the circuit isn't working, but I can't be sure since I haven't tried to build it yet.
On another note that may be of interest to anyone experimenting with 12FQ8 tubes it can be used as a high gain dual triode if you examine the datasheet closely. By grounding one plate in each section a gain of 95 is stated in the datasheet. I built a circuit based on recommendations from someone on the Antique Radio Forum and it works well using a B+ of 150V volts. I also tried this on the 12V Valvelitzer circuit and it was a huge improvement.

[sluckey]

I noticed there is a what may be a flaw in Laird's schematic when comparing it to his layout. In the schematic the 3M reverse audio pots have all 3 lugs connected, but in the layout only 2 are connected. Sluckey have you tried disconnecting those lugs as per the layout? Maybe this is why the circuit isn't working, but I can't be sure since I haven't tried to build it yet.

The speed pots are being used as a simple 2 terminal variable resistor. It is good practice to connect the unused terminal to the wiper, but the pot will work either way. Makes no difference either way.

[Greyrocker]

That does make sense. I'm thinking that using all 4 plates might be the problem. It may be dropping the gain, One thing I tried was to use the 12FQ8 as a 4 output multi coupler but it wouldn't pass signal. It seems to me that what Laird was trying to accomplish may've been to clone a Fender Harmonic Vibrato, which is actually a tremolo/amplitude modulation circuit. Laird's concept is a great idea & I think his circuit is a good starting point to develop into a working prototype that he hadn't been able to finish during his short life. I hope that we can work together and share some ideas on how to make his concept work. The idea of emulating a Leslie cabinet is far from new. This may be part of what Laird was trying to accomplish. He describes his tremolo as being asymmetric and that is what intrigues me.
What occurs inside of a Leslie cabinet is a very complex mixture of amplitude modulation, aka tremolo, frequency modulation, aka vibrato and various levels of phase shifting and phase cancelations. Putting that aside for a moment and concentrating on only the amplitude modulation, an asymmetric tremolo is a great idea. Since you have actually built one and I haven't, I'd like to know what effect, if any, the circuit does to the input signal. What have you heard at this point?

[sluckey]

I didn't build this. The guy who did is PassoGavia and his didn't work. I have no idea why. He started this thread and then dropped outta sight.

[Greyrocker]

Thanks for your input, Sluckey. I am new at posting on a forum and hadn't noticed I was addressing the wrong member. I guess this thread is going nowhere since he dropped out.