AC30 TB Problem

[buckshot]

G'day All,
Just a quick Q about my 67 AC 30 TB. Maybe some one can help. When I switch it on I get a slight crackle sound and then when I plug in the guitar lead no volume comes. Sometimes when I turn the vol. up full and pull it back it starts to operate normally. Then sometimes if I switch the amp on and off a couple of times it also starts. I have checked all the valves and have sprayed CO Contact spray all around the place. Any ideas what the problem might be?
regards
Buckshot

[RUSSET]

Could be a dodgy jack plug connection ? Check out the wiring in the plugs.

Tony.

[David Martin]

How did you check the valves, Tom? My understanding is that you need to substitute for a known good valve one at a time...

[buckshot]

Thanks Tony & Dave. It happens in all plugs so it's not just one. The valves I put in are new( well, 6 months ago) .I put in a matched quad lot of well known brand. I thought maybe it might be the on/off switch?
regards
Buckshot

[David Martin]

Some valves give out after only 6 months... check the GZ...