Replacing rca jacks on sf twin reverbs

[rockman627]

I had to replace the rca jacks on a sf Twin Reverb 100 watts with mv. The replacements did not include lock washers, so I thought they were unnecessary. Well, if you don't use them the reverb doesn't work. I wrote out a long post asking you guys to help me figure it out, then I thought about those washers and put them in. Voila! I guess the ground doesn't connect well without them. I pass this info on.

[Jazz P Bass]

Thanks.

[g1]

I'll also mention that oxidization at those star washers can create hum issues in the reverb circuit.

[Tom Phillips]

I find that, during refurbishment of an amp, cleaning and tightening of mechanical ground points is a significant requirement to reestablish good performance.

[drewl]

Yup to all.

[Helmholtz]

What is an "mv" jack?

[Pedro Vecino]

What is an "mv" jack?

I think he means a Silverface Twin reverb with master volume.

[rockman627]

Yes, sorry I was unclear.
Strangely, when I used my rca to 1/4 in cable to test reverb in and out I good signal without the washers. So signal was going into and out of the tank but there was no reverb. Everything tested ok but there was no reverb. That's when I turned to you guys. That little tech on my shoulder told me to put the washers in, even if it made no sense.

[Helmholtz]

Thanks.
Now I see, this is a MV Twin and the RCA jacks had to be replaced.
The reverb send jack gets its ground via the chassis only.
As this is the output of a low impedance (8 Ohm) power amp, it's essential that you have a good, low resistance ground connection here.