Formula Pre problems, thoughts?

[tim6string]

I have a Formula pre I have been using live for over 1 1/2 years. Last night I changed all the preamp tubes and could only get the clean channel. The channel switching worked, but nothing.

I tried swapping an old tube back in through all the positions, no change.
I tried disconnecting the foot switch and switching manually, I did notice very low volume on lead 1 and 2 but not always.

I tried it again for 3rd set and it seemed to be working fine (no real changes, just seemed to start working) during the 3rd set lead 2 seemed to fade away breifly but came back and seemed to work fine.

I think it is time to take it in, but other than the description above, I have no clue what is really going on and if the problem could be easily found?

 

[tim6string]

FYI, for the first set I used the clean channel and put a TS9 in front and it worked fine, didn't sound very good, but seemed to have no problems, so it seems to be a lead 1 and 2 problem.

 

[daveyboogie]

Could you see if all the tubes were glowing properly? Just wondering if it could be a heater circuit problem... New set of tubes with lower heater series impedance could have stressed the circuit somewhere. Similar thing happened to my power amp after a tube change.

 

[tim6string]

I will check that out. I have noticed the preamp tubes (even in the past) have always been hard to see glowing.
The new tubes were all Mesa 12ax7s.
I am going to open the unit up and take a look inside as well.

It probably is heat related. After it ran for awhile the other channels did start working (but there was the fade, to almost clean)

 

[tim6string]

I just spent some time with the pre and all the tubes were warm and glowing. I did clean all the tube sockets and lubricated them with deoxit and proGold. They did go into the sockets pretty hard and they go in much easier. After messing around for an hour or more I didn't notice any problems... So maybe?

I saw some other internet stuff on pres not having the lead 1 & 2 channels not working.

Does any one know if they are gold plated sockets like the old Mark IIIs. I know those were a problem. The gold would start to flake off and cause the tube to arc...

 

[tim6string]

I played a gig last night with the pre and had no problems. Another gig tonight. Let's hope cleaning the tube sockets was the ticket.

 

[daveyboogie]

My Formula is due for a re-tube soon, too... I'll let you know if I have any similar issues....