Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Searing on August 01, 2019, 12:29:41 am

Title: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Searing on August 01, 2019, 12:29:41 am: as the title says. It’s on both channels volume pots? Middle lug. Amp turns on, makes odd noises, volume is present even on 0. I can’t find the issue? Is it normal to have continuity between the chassis and the middle lug on the volume pot? Can’t be!
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Deric on August 01, 2019, 12:47:40 am: If the volume pots are turned all the way down, yes that is normal.
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Tony Bones on August 01, 2019, 01:28:47 am: You mean with a multimeter set to buzzer mode? What were you hoping to learn by poking around with that thing?
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Searing on August 01, 2019, 06:24:53 am: I have signal even with the volume at zero. And, static.
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: shooter on August 01, 2019, 08:30:17 am: Quote
Can’t be!
put a gator-clip on center lug then ground to a really good ground, not a floating wabbly crappy one :icon_biggrin:
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Searing on August 01, 2019, 01:58:37 pm: Ok. It was a bad connection at V2. But, now I am getting intermittent static when I push on the phenolic board. Almost as though it is conductive?

And, whenever the dehumidifier in my basement turns on, the amp motorboats. This is a Super Reverb. I just recapped it.
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: shooter on August 01, 2019, 03:28:14 pm: Quote
Almost as though it is conductive?
welcome to old fender boards, pretty well know problem with only ONE good solution, replace it. you can try separating the layer, elevating the board, insulating the layers, an on an on......................
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Searing on August 01, 2019, 08:51:39 pm: Insulated the top of the bottom phenolic board with some insulating tape. Seems to have worked. But, fuse kept blowing, and I saw the PI turn blue/white. Turns out the socket is damaged as one of the pins is broken and jammed deep inside. This amp was abused! I increased the value of the resistors on the three 22uf main filter caps hoping this will stop the motor boating. We shall find out once I get that new PI socket delivered.
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Willabe on August 02, 2019, 09:26:02 am: Quote from: Searing on August 01, 2019, 08:51:39 pm
Insulated the top of the bottom phenolic board with some insulating tape.

Ok, but, the eyelet board can be conductive from eyelet to eyelet, very common.

Sometimes only certain sections/areas are conductive.
Title: Re: Continuity between chassis ground and middle lug on volume pot in Super Reverb?
Post by: Searing on August 06, 2019, 12:01:51 am: I figured out why the amp was motor boating....I hooked up the main caps wrong. Rushing the job! Need to SLOW down!