Need reverb jack advice

[Lectroid]

Wiring a Tweed Deluxe Reverb circuit by sluckey, my first amp with reverb.  I have a 4AB3C1B MOD tank and two RCA jacks for the back panel.  I bought jacks that said they were "naturally insulated."  They arrived without insulating washers, and with large grounding tabs. They will be grounded to the chassis when installed.  To avoid a ground loop, are there special insulating washers I need to buy?  Will the fiber washers I use on inputs do the trick?   

I tested the tank; the input is Insulated and the output is Grounded, as advertised.

I've read up on many posts here about reverb wiring.  In one, PRR suggested leaving the input jack (to tank) floating, and grounding the output jack (from tank), and that matches up with the tank's own grounding scheme. Please chime in if you have a different POV.

The other question is once I isolate the jacks, I'll need to ground them somehow, according to the schematic.
Where is the best ground point to connect up the ground tabs from the two jacks?  I've read suggestions to use the cathode ground of the reverb driver and also to ground that driver tube's cathode to the B+ power amp ground since the driver tube is using the "B" screens node for its plate voltage.

Also, any other advice on a first-time reverb build?


As always, many thanks for any help.

[sluckey]

Fender did not isolate the amp jacks from chassis. Neither did I.

BTW, the only thing tweed about my TDR is the cabinet. The circuit is straight AB783.

[PRR]

... jacks that said they were "naturally insulated."...

Good. The artificially insulated jacks don't taste right.

Didn't Fender eventually "rivet" the jacks? No threads, just bashed-over the back end of the shell onto the chassis metal.

[Lectroid]

Thanks, guys

So I conclude that I should not wire anything to the reverb jack ground tabs, in fact I could easily leave them off.   Just screw the jacks down to the chassis and move on.

[EL34]

One end of the Reverb tank itself should be isolated from ground
You can check that with a meter

That way you do not have two paths to ground

[sluckey]

So I conclude that I should not wire anything to the reverb jack ground tabs, in fact I could easily leave them off.   Just screw the jacks down to the chassis and move on.

You need the ground lugs. Wire them like this pic. Left to right---> send, return, reverb FS, vib FS. Reverb transformer black wire connects to return ground lug. 220K connects between return tip and reverb footswitch ground lug, with return tip and FS tip jumpered together by 220K lead.

     https://el34world.com/Hoffman/images/Img_8415.jpg

[Lectroid]

sluckey,

Thank you, I will do it that way.  But I don't fully understand it.

The RT lead goes to the reverb send jack. But you suggested to ground that jack to the chassis.  So wouldn't that ground the tank's input jack via the shield on the cable?  The tank Input jack is itself isolated, and PRR suggests to let the ground float on the input.

What am I not understanding?  Is it because the input jack itself is isolated--it's shell doesn't actually connect to the tank cover's ground?  The tank ground has no path connecting it to the chassis ground?

One other thing.  For the tank cables, is it OK use a pair of the standard cheap stereo connect cables we all have so many of?  Is it decent-enough shielded cable to use for the input jack to V1, for example?  I'd love to finally have a use for them.

Thanks!

[mresistor]

One other thing.  For the tank cables, is it OK use a pair of the standard cheap stereo connect cables we all have so many of?  Is it decent-enough shielded cable to use for the input jack to V1, for example?  I'd love to finally have a use for them.
Thanks!

Yes  I use stereo cables as extension cables to connect the reverb tank in combo cabinets when I have the chassis out on the bench, no problem.  They work fine. Seems like they would be ok for the input to V1 too.

[Lectroid]

Great.  Thank you.

[sluckey]

What am I not understanding?  Is it because the input jack itself is isolated--it's shell doesn't actually connect to the tank ground?

Yes. The input jack shell is insulated from the tank chassis. The input jack simply connects to the two wires of the input transducer, nothing else. The return (output) jack shell does contact the metal chassis for the tank. This shield provides the one and only connection between the amp chassis and the tank chassis. Since there is only one electrical connection between the amp chassis and the tank chassis, there can be no ground loop.

One other thing.  For the tank cables, is it OK use a pair of the standard cheap stereo connect cables we all have so many of?  Is it decent-enough shielded cable to use for the input jack to V1, for example?  I'd love to finally have a use for them.

That's fine. I do it. Lot's of others do it too. Here's one example...

[mresistor]

Some of the newer fender amps have the equivalent of rca stero cables going to the tank .

[Lectroid]

sluckey,

Thanks for the explanation.  I had the gist of it, but you cemented all the fuzzy areas perfectly!  I am wiring them up right now.