I just purchased a Marsh 64 Vibroverb clone. the volume pot on the vibrato channel does not give any sound until 2. i made sure the knob was set where normal and not over adjusted. i looked inside the chassis and going by part number, saw that there is a 500KA Pot in there. I read that these should be a 1meg audio pot. is this my issue?, can i just install a 1meg and be done with it, or will other components have to be changed? ive fixed tube sockets,biased ,soldered pickups and pots before so im thinking i could do this on my own...unless not....thanks to anyone with info!