Crate Vintage Culb 50 (reverb starts at 5)

[punkykatt]

http://el34world.com/charts/Schematics/files/crate/crate_vc3112_poweramp.pdf

Hey Guys, Have a Crate VC 50 on the bench. The reverb starts to work only  when you turn the pot past 5. This amp has two channels with two separate reverb pots for each channel.  Both pots work the same in each channel.  The schematic is calling for 10kA pots , when I put my meter across the outer legs of the pots I get 5k?? I tried two others meters and I get the same readings.  Would a 5k pot cause the problem of the reverb not starting until past 5?   There is plenty of reverb  from 5 to 10 on the dial.  Thanks in advance for any input.  Punky

[sluckey]

I wonder if those pots would read correctly if they were pulled from the circuit?

[punkykatt]

sluckey, thats is what I was thinking.   I was hoping to save some time.  If the pots turn out to be 10k, what would cause the non function between 1 and 5?

[HotBluePlates]

Perhaps poor contact from the wiper to the resistance track. In which case you'd have to pull the pots anyway to replace them.

[2deaf]

If the amp was powered down when the pot. measurements were taken, there would have been no voltage on the gates of the J112 FET's and they would have been conducting so that you were measuring the pot.'s in parallel.

Not getting any signal until the pot. is past 5 could be a problem with the FET switching.  You could try checking the gate voltages when the channel switch is in each position for starters.

[punkykatt]

Thanks for the replies Guys. Much appreciated.