Has anyone built a working Stout "Reverb" Amp? (Solved on 10 July)

[dram56]

I just finished building one per the latest drawings and schematics.  The reverb is non-functional.  Only produces buzz, hiss when engaged.  I have checked and rechecked my wiring from V2 through the reverb transformer, Input and Output reverb tank jacks, Dwell and Mix pot wiring and back to the board and through V3.  Everything checks out good.  Tried replacing the brand new tubes and tank with different new tubes and tank.  I thought it may have been a grounding issue with the Input and Output RCA jacks.  I have tried having them both grounded to the chassis (as shown on the schematic).  I have tried Isolating the Input jack and leaving the Output jack grounded.  I have tried isolating the Output jack with the Input jack grounded and finally, Isolated both Input and Output jacks.  No change.  I have tried not using the footswitch, which leaves the reverb engaged.  Same buzz with no actual reverb output.  So, not the footswitch.  Something else that might be worth mentioning is the Dwell pot has No effect.  And when you turn the Mix pot from 1 to 10, there is No effect on having reverb, but the buzzing disappears once you get the dial turned all the way up to 10.  I thought perhaps I had wired the pots backwards, but they match the schematic.
The amp seems to function properly when no using the Reverb.  Volume, Tone and optional Gain pots all work as expected.  Voltages to all the tubes are all within spec.  The amp is loud and has a lot of Gain.  The optional Gain pot helps tame it down, just as I had hoped.


Now, it is quite possible that I have overlooked something in my debugging, but I have checked everything over several time during the past week, and still made no progress.  One thing I have not verified is my brand new Hammond 1750A reverb transformer.  I suppose it could be faulty, but I have verified it is wired correctly (red wire to B+ , Black wire to ground, Green wire to the Tank Input jack tip, and the Blue wire to V2 pins 1 & 6).
I have actually drawn a modified circuit that should work, but before I go to all trouble of re-configuring stuff, I would really like to actually hear one that someone has built per the newest original schematic, that has a working reverb.  If so, please point me to it.  And if I know that it can work as drawn up, then I will continue debugging my example.
Thanks for any assistance. 

[thetragichero]

when troubleshooting reverb i like to plug an rca cable between send and return. the reverb pot should now act like a horrible sounding treble boost. lots of gain. if that's not working then something is wrong with either the send or recovery. try to rig a 1/4" to rca cable and plug a guitar into the reverb return jack. if you get nothing, something's wrong with recovery stage (i'm just thinking of this now and i have a build with nonworking reverb so thank you for making me think of something to try!). if you do get signal then something is wrong with the driver stage. you could also use a scope with signal generator and dummy load to avoid listening to likely terrible sounds. what works for me in troubleshooting is divide and conquer, figure out what the problem isn't to give you an idea of where to focus on

[sluckey]

Wiring error first, then incorrect component values are the most likely suspects.

[dram56]

Thanks for the reply "thetragichero". 

I agree, divide in half, then divide in half, repeat.  Tried and true troubleshooting technique.  And take nothing for granted.

I am not sure if there is any Input going to the tank, but I do know for sure that there is no Output coming from the tank as indicated by NO crashing spring sound if you bang on the tank.

sluckey
I have verified that ALL of the component values starting at the Guitar Input Jack and ending at the speaker Output Jack are correct.  There could still be a wiring mistake on my part that I have yet to find.  Same set of eyes can easily overlook the same mistake.  But, I sure would like to hear a working example of this amp, just for a sanity check.

[PRR]

> when troubleshooting reverb i like to plug an rca cable

That's a little drastic. The Send is about 1,000 times stronger than the return. (at least for the trebles.) You'll blow your ears out. Or if nothing comes out, what have you proved? OK, it is not JUST the tank. But is it the send? The return?

This is much more trouble but gets closer to the problem. Take the tank out (or at least disconnect). Figure which side went to the transformer or the big tube. Hotwire a speaker there. Plug axe, turn up knobs. Does it play like a pocket radio? If so the send is working. The even easier part: tap your finger on the return plug. That should be a BIG buzz, which you can turn-down with the return pot.

[dram56]

*** SOLVED ***

OK.  It's ALWAYS something stupid when you you find the cause of an issue on a new build.
It turned out to be a bad ground connection on the FOOT SWITCH Jack.  I thought I had scraped off the powder coating on the inside of my Hammond chassis.  I knew the outside of the chassis had paint on it, but I thought I had a "good enough" ground from the outside of the jack to the inside of the chassis...but apparently, I didn't.  I took a dremel to both the outside and the inside of the chassis where the RCA Foot Switch passed through and it started working.  I did the same to both the Input and Output Tank Jacks to be sure they were also good.
Everything is working as it should now.  You can get real surfy with it if you crank up the Dwell.
I appreciate the help from all that responded. 


Once I get the amp finished up, I will post some clips.  ** Update **  see my next post for a link to my sound clip.


Thanks everyone.
Dave

[dram56]

After correcting the Reverb issue (a bad ground connection at the Foot Switch RCA Jack) the amp sounds very good to me.
Here is a clip that I made right after getting the reverb to work yesterday.  Boring stuff, but hopefully it demonstrates how the amp sounds (at LOW Gain) with and without the reverb section engaged.  Fender Strat plugged straight in.  I am using a 2 x 10 external speaker cab with 2 Weber ceramic magnet speakers.  I believe they are Weber 10F125 speakers.  Anyway, it sounds pretty good to me.
https://soundcloud.com/dave-ramsey-949064652/stout-18-watt-british-style-amp-with-reverb_first-test-recording

I am mounting this chassis in a Head cab.  BTW, the chassis that I used was a Hammond 17" x 10" x 2" steel blank chassis box.  The layout was my design, the schematic was created by Doug around Jan 2006 I believe.  I built mine with the optional Gain pot (which really helps when using the reverb).  I did however decide to skip adding the "Hot Switch" as the Gain pot seem to give me all the Gain that I desire when turned up all the way, and mellows out nicely when set to around 3 - 4.  The only other mod that I did to the original design was change the first dropping resistor from 4.7K 3W to 10K 3W because all of my B+ voltages were a bit too high.  This resistor change brought everything back into spec if not slightly on the low end of spec.  I suppose if one were really picky you could make that resistor 6.8K, but I think it sounds very good to me, and it has plenty of Gain when you turn the Gain pot up.  I used all JJ tubes and Hammond transformers.
As you can see from the attached images, it looks a bit rough (cosmetically) at the moment.  But I wanted to capture a sound clip as soon as it was working.  And my recording setup was crude to say the least.  Just a Tascam DR-40 placed directly in front of the speaker cab.  And the acoustics are not great out in my man cave workshop.  Lots of stuff rattling, hence why I only made this first clip with relatively Low Gain.  And I am no guitar player.


Dave