Has anyone had RF Interference problems with their Express?

[ampmodster]

I have a Ceriatone/Toneslut kit that is picking up a local FM radio station. I have the input shielded and also shielded the run from the volume pot wiper to V1 pin 2. I also added resistors at the grids of these two stages. These things helped, but still not fixed completely.

The pickup area seems to be the bright switch. The problem is worse with one of the bright caps switched in.

Any Ideas?

[paulster]

Have you got the underside of the chassis shielded somehow (e.g. copper or aluminium foil at the bottom of the head case)? Mine was slightly susceptible to RF without its chassis cover plate attached, but then everything is susceptible to RF in my house!

[drz400]

What is your ground layout?
If you have only one ground buss and terminate it at the input jack as well as the input jack to chassis you will have no RF

IF you have a ground buss and termintae somewhere else to chassis then run a .01 cap from the input jack ground to chassis ground right near the jack

[gtrcollectr]

You may need to add a small grid resistor on the input. I had a similar issue on a liverpool build and a 68K fixed it.

[paulster]

Mine didn't need a grid resistor or the cap on the input jack, just a plate on the bottom of the chassis was enough, and my chassis was built with one anyway.

I seem to get loads of RF where I am as pedals, guitars, everything(!) is prone unless shielded.

[ampmodster]

Thanks drz400 for the suggestion of the cap at the input jack. That fixed my problem.