Ground lift. Keep or remove?

[plumcrazyfx]

I have a very late-run (1979) Traynor YBA-1 in need of a cap job and general updating.  The amp seems to have come with the 3 prong by this time.  It also has an accessory jack and a ground lift switch.  A quick inspection shows a .0047uf cap and 12ohm resistor on the switch for the ground lift.  I don't see a standard death cap in the chassis.


I guess I'm wondering if I leave it or of it should be removed for safety.




 

[sluckey]

Keep it.

[pdf64]

Do you mean that the switch breaks the direct connection between the amp's chassis and mains ground (eg puts a cap and resistor in series with it)?

[sluckey]

I believe he means this...

[PRR]

It is a fall-back for when you only have a 2-pin wall outlet. Quite possible even past 1979. It allows you to throw a cap to either side of the line to reduce buzz. If you DO have a proper 3-pin wall outlet, it basically does nothing.

Yeah, I'd keep it too.

[plumcrazyfx]

Yah.  It looks like that schematic.  3 positions labeled ground ground and ground lift.

[ac427v]

Wish I had wired my amps like that! Moving the switch to the lower position uses the 12 ohm resistor to isolate the "circuit common" connections from the "earth ground". That means the amp ground wire to the house ground doesn't have a direct connection to the input jack ground. I could use my 120volt stereo chorus pedal with two amps without the extreme hum from the ground loop formed by the power cords and input cables. Great feature for those who use obsolete pedals.Craig