isolating reverb jacks...

[hesamadman]

I know on the reverb pan you want to isolate the jack from the tank. Does this also apply to the chassis? I have a ss reverb from a blues jr in an amp. I use to have rca cables hard wired through a hole in the chassis. I just took them off and added some reverb jacks to the chassis. The reverb works but Im getting all kinds of feedback and overall weirdness. Im assuming that ive created some serious ground loops. I dont know why I didn't just isolate them to begin with. Any thoughts?

[hesamadman]

Answered my own question. Removed the jacks and went back to hard wired. Works great. Ill isolate the next one. And I found a cold solder joint in the reverb. Had some issues a while back. Posted a thread about it. Wasnt getting all the reverb I should have. It came and went. Found the culprit!

[2deaf]

The input side needs to have both conductors isolated from the chassis and the tank.  The output side has to have the shield connected to the tank housing and to ground on the amplifier.

[hesamadman]

My reverb tank jacks are actually completely isolated from the tank. I havent used a reverb that isnt this way, but I havent done many different reverbs.


At this point my reverb circuit goes to one single ground point. No jacks are grounding on the tank or chassis. This is the only way my reverb is happy

[Willabe]

1 of the tanks RCA cables ground should be connected to the tanks chassis so the tanks chassis acts as a shield.

[hesamadman]

1 of the tanks RCA cables ground should be connected to the tanks chassis so the tanks chassis acts as a shield.

Would It benefit to attach it somehow? Mine is 100% isolated. Both jacks.

[Willabe]

Yes it should.

1 of the tanks RCA cables ground should be connected to the tanks chassis so the tanks chassis acts as a shield.

(And the amp chassis jacks have to be grounded.)

[Willabe]

The weakest signal in the amp is in the verb springs, the verb output coil and the output cable going into the verb recovery stage. Even less signal than from the guitars PUP's.

So it needs shielding where we can put it.

[Mike_J]

I was looking at different reverb tanks for my Deluxe Reverb build lately.  As I recall different reverb tanks have different grounding schemes although none of the tanks that I saw had both the input and output jack grounded.  If you look at the techsheet for the particular tank you have you should see which side of the tank gets grounded from the factory.


Having all reverb jacks isolated and run to the negative side of the cathode cap for the reverb circuitry for grounding is good practice from what I have read.  I have also read that it is good to place a steel plate on the open side of the reverb tank to keep PT interference out.  Additionally, one guy wrapped his tank, all six sides twice, with aluminum foil and fixed an oscillation problem that way.  He used the vinyl bag with the aluminum foil. Another guy wrapped his amp in a cover made from mu steel which is supposed to be very expensive but it cured his oscillation problem.  Had to get all six sides of the tank covered or it didn't work.


Thanks
Mike

[hesamadman]

Ah.........my reverb tank is a tricky little booger. I see why it wasnt grounded on one side. Thanks guys
.

[Smooth]

Okay guys, I'm a wanna be tech. I have been learning over the last couple years thanks to guys like Aiken, Merlin and Kevin O' Conner. And several others. A great thanks to these guys for free advice.

I also am building a similar amp to the Deluxe Reverb. It is a single channel reverb amp without tremolo. I have a couple conflicting opinions with the mentioned advice. I came here looking for opinions, so don't think I'm here to bash. I'm just offering my view on it that differs from the previous advice. Feel free to teach me if you know better.

The 4ab3c1b tank has a grounded output and an isolated input. I'm thinking this means the tanks input is isolated so the reverb tranny secondary/sending jack can be grounded and it won't cause a ground loop through the tank. I believe the reverb tranny secondary/send jack should be isolated from the chassis, but it should tie a common connection with the return jack's sleeve at the cathode of the reverb recovery/return amplification stage (return jack is isolated from the chassis too). In the case of the Deluxe Reverb, the cathode of V4A.

Then the reverb jack sleeves should go from that common connection to the chassis ground where B+4 grounds (negative lead of the X supply in the DRRI).

If the send jack isn't grounded the sending reverb cable is not shielded. Not shielding the sending reverb cable could also be the reason for some reported oscillation.

To the best of my understanding, this follows Aiken's grounding scheme.

IMO, if following a star grounding scheme, the reverb jacks would ground at the cathode of the reverb recovery amplification stage, not the reverb driver stage. The secondary of the reverb tranny is isolated from the primary. I mention this because the primary is powered by the higher voltage B+2 Z supply.

IMO, the only thing that should ground to the B+2 Z supply is the 1M V3A and V3B grid leak, R26 and the V3A and V3B cathodes should share a common with R26 too. Then run to the negative lead of the B+2 Z cap for grounding.

This is the best I can come up with. lol