Intermittent static on my Mark IV

cesjr · Jun 16, 2006

Today I turned on my Mark IV, played for a few minutes and I started getting real bad static through the speakers. The static is apparent on all three channels. It also seems to come and go periodically.

For anyone who saw my post on the "tubes" section of the forum my power tube sockets are loose. So this is my best guess as to the cause of the problem, unless there could be another problem with my amp?

Any help would be appreciated guys, thanks.

cesjr

Boogiebabies · Jun 16, 2006

Could be a dirty pot in the EQ or Master Volume. If your tube sockets are loose, you can tighten them up with a small flat head jewelers screwdriver and spray them with Caig Pro-Gold. It could also be a preamp tube.

cesjr · Jun 16, 2006

Nothing changes when I turn the pots. During the re-tube I cleaned the sockets with Caig Deoxit applied Pro-Gold to the pins. Could it be the loose sockets? I notice I can get the static to start when I tap the top of my amp leading me to believe it is the loose sockets.

Also if it is a preamp tube, could I narrow down the possible faulty tube by the fact that the static occurs during all three channels?

Boogiebabies · Jun 16, 2006

The sockets are chassis mounted. There are two ways to tighten them if the whole socket is loose. There are four metal clamps that hold the socket to the bracket. You need to bend these down to tighten the hold on the socket.
The other is to try to tighten the brackets to the chassis. If they are stripped and just spin, you might want to try a slightly larger screw or used a small bolt with lock washers. I have had done both types of fixes to loose sockets and transformers. I would also try a different speaker ans speaker cable.
I hate not being able to track down a problem myself. Right now I have two amps that fart when I shut them off. it is driving me nuts because they never did it before. They also have not been played in months.

Keep trying and you may just get it.

cesjr · Jun 16, 2006

Boogiebabies, I really appreciate your time and help. Sorry, I really didn't word my last post correctly. The tube sockets themselves are fine; however the metal contacts which hold the pins are loose. I previously had a set of Sovtek, and then for a brief period a set of Chinese 6l6's in my Mark IV. I just replaced those with Winged C's. The pin diameters are different. Both Sovtek and the Chinese pin diameters averaged 0.094 inches. The Winged C tubes are slightly smaller at 0.091. At the moment I can very easily slide them in and out. With vibration I'm afraid they might even fall out.

Anyway I managed diagnosed my original problem. During the time when my amp goes into static I checked each power tube by gently wiggling them back and forth. When doing this with the second tube from the left, the static stopped. I tried it again, and got the same result. I pulled that tube and applied more Pro-Gold. For now everything works great, but I still should tighten those socket "pin holders."

Any information on how to do that?

Boogiebabies · Jun 17, 2006

Yes, a small jewelers flathead screw driver. Basically you want to bend the contacts back toward the middle if the pin hole so they grid the tube pin again. Just gently pry them and you with have tighter grip on the pins.