6G16 Vibroverb 6V6 build

[carausius]

  Hi, My first post here & another newbie in the ranks

I've built a Vibroverb 6G16 with 6V6's (built in a Deluxe Reverb chassis with a DR PT, & a DR 4/8 ohm OT) it's in a 2 x 10 combo with an old pair of JBL E110's @ 4ohm. 

The amp works & sounds great on the normal channel & the vibrato footswitch works fine, however the reverb channel has some problems, there's some hum & slight distortion & no reverb signal at all . Controls on the reverb channel seem to work although the volume pot seems maybe a bit scratchy.

Here's the voltage file link  http://www.el34world.com/charts/valve/ValveData.php?e=view&f=11063

I'm not sure on the correct reverb return / send & footswitch wiring, I have used RCA jacks with isolation washers on both sides & then wired the ground lugs on the RCA jacks to a lug on the chassis nearby. I've seen these done many different ways so maybe my problem is around this area? A grounding issue perhaps?

Any advice on rewiring the reverb in / out / footswitch section or anything else I might have overlooked would be greatfully received!!!!

[firemedic]

If you built it strictly according to the schematic, V3 pin 6 should be connected to V3 pin 1, and show the same voltage.
If you went to the trouble to isolate the RCA jacks then you may as well ground them to the same point as the reverb tube cathodes. There are many opinions about this but it has worked well for me. In fact I ground the reverb send tube to the main ground, since the reverb transformer is connected higher up the B+ rail than the rest of the PA. But you should still get reverb regardless of where you ground the jacks.
Have you reversed the tank connectors perhaps?
Scratchy pots mean DC on the pot which means a leaky coupling or tone cap. If it's very leaky (like the cheap chinese "mallorys" I should have never bought) it will throw off the bias on the next tube so badly that it will never sound right.
Leaving the tone caps connected to the V2 plate, disconnect the other ends from the tone pots & check for DC voltage leaking thru while powered up. There should be NONE.

[carausius]

Thanks for the reply Firemedic,

Lastest news finally getting back is that I put together one of Doug's listening amp devices & went through the circuit, at first I thought it was the usual volume pot crackle on the bright (Channel 2) , hiss & distortion as I heard before, however when I bypassed my Weber Mini Mass which I had at full volume reduction so I could listen to my amp listening output, the problem seem to have disappeared!!!! I also had a scratchy pot on the guitar I was using to test, a '88 Ricky 330 as well as the Webers scratchy pot!!

Before when I tested the amp I had an old reverb tank which I'm not 100% sure works anymore so I'm ordering a new one. Anyway it seems that the output to the reverb tank input is OK judging by the clear guitar signal being sent, also if I plug a cable into the reverb tank return input jack I get a similar humming sound to that when you touch a guitar cable with your finger so I'm assuming that side is OK? I've not no DC voltage on any of the pots so far, apart from the vibrato which works fine.

So far I'm prefering the normal channel on this amp, the brownface controls seem to have more sparkle. The bright channel is not as thick sounding, maybe it's the volume pot silver mica cap @ 47pf on mine ?? I also prefer the lower gain 2nd inputs on each channel on the guitar I used at least although I'm going to check with different guitars to get a better idea. The Vibrato sounds cool, my brother said it sounded like an old alien invasion movie when he heard it!!!

So just waiting for a new reverb tank & give everything one last check & hopefully the amp is fine, I'll report back then

Cheers!!

[carausius]

So tried a new MOD Reverb tank & traced the circuit with Doug's listening device, the Reverb recovery signal was getting distorted so a bit of reflowing of two joints & it all now works fine. I think the new MOD tank sounds better than the old Accentronic one I have in my '72 DSR / Twin Reverb combo, maybe the old one has lost it's mojo!! I still slightly prefer the Normal to the Bright channel on this amp, will have to work with the tone controls to see what the exact difference is & also try a preamp tube swap.

Wondering what to build next when I get the funds together??? 

[tubeswell]

Wondering what to build next when I get the funds together??? 

The eternal question init?