Laney Supergroup 100W grounding.

[diy didi]

Hi guys.
I recently started repairing a Laney Supergroup 100W amp from the 60’s.
I pretty much completed the restoration, but I’ve been wondering about the grounding scheme the designers implemented. There is a slight hum with all controls full.
Turning down the the two channel volume controls, kills it.
The amp uses a form of star grounding at the presence control. The presence control body is the only connection made to chassis. A buss bar runs from input socket grounds to all volume control and tone control grounded terminals. The input and speaker output sockets are plastic and isolated from chassis.
Are there any modifications to improve the grounding, that I can do?
Any problems with the way they did it?
Thanks in advance!!

 

[PRR]

There's always heater-hum. (DC heaters were real rare in 1960s.) It really should be audible full-up. However if you plug-in and turn-up a guitar, the pickups will pickup more hum from the room. And on most 100W amps, if you brush the strings nobody will be hearing hum.

I would be freaked-out by an amp like that which had NO hum. That's the sound of electricity!

 

[turk 182]

Hi guys. There is a slight hum with all controls full.

there's not a snowball's chance in hell it would ever be operated that way...these amps are crazy loud

Turning down the the two channel volume controls, kills it.

if this wasn't happening then you'd have a reason for concern.

Are there any modifications to improve the grounding, that I can do?

not likely...

Any problems with the way they did it?

no.

 

[nigelwright7557]

I used to have a similar amp a Simms-Watts 100W PA amplifier.
That had a slight hum with volumes all turned up.

Amazingly loud for 100 watts, it blew away my Maplin disco 225WRMS SS power amp.

 

[diy didi]

Thanks for the input guys!!!