Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: quayhog on March 09, 2019, 05:26:37 pm

Title: 120VAC pilot light
Post by: quayhog on March 09, 2019, 05:26:37 pm

I have a noisy Hilgen B2501 amp on my bench.  I’ve cured much of the noise issues, there were many.   The amp has an AC pilot light that runs directly off mains, possibly neon.  It doesn’t light until the variac is above 50VAC.   


Are these known to induce noise into an amplifier circuit?  Is there a cure without replacement?


The wires are mostly perpendicular to any wiring. The amp now has New caps, upgraded grounds and elevated the heater CT to 22VDC.

Title: Re: 120VAC pilot light
Post by: Papa Jim on March 09, 2019, 06:02:17 pm

my amps pilots all run off the filament voltage

Title: Re: 120VAC pilot light
Post by: shooter on March 09, 2019, 07:02:32 pm

just take it out for a quick test of noise, pretty sure you'll know when there's power  :icon_biggrin:

Title: Re: 120VAC pilot light
Post by: sluckey on March 09, 2019, 07:56:08 pm

There are plenty of 120vac neon indicator lamps in big name amps. Most of my home made amps have neon indicators. I prefer them. I'm not aware of any noise issues.

It takes about 90v to fire a NE-2, the most common bulb used in amps.

Title: Re: 120VAC pilot light
Post by: Colas LeGrippa on March 09, 2019, 10:12:08 pm

No noise issues with neon bulbs in my builds
What about elevated heaters ?