Tube problem?

[Killtone]

Actually I am pretty sure it is a tube problem, but I am not sure if it is a power amp or preamp tube. I have a Mark IV.

The problem is when I let a chord ring, the volume level becomes inconsistant and on a clean tone it starts to break up in a weird way. Also, with higher gain, all the gain is there at first, but when sustaining a note it dies out sooner than it should. The cleaner the tone, the more obvious the problem.

I have switched power an preamp tubes and I can get it to sound better, but sustained notes or chords never sound as smooth as they should. I am guessing that my amp is being a little picky about which tube I use in V1.

Any suggestions or ideas?

BTW: Hello everyone! This is my first post here. I have been on the Randall board for my RM100 and just found the Boogie Board. These are great places to share info.

 

[6L6C]

You might want to check your caps also.

 

[Killtone]

Thanks for the tip. I don't know much about electronics, so you'll have to excuse my ignorance on this. How would I check the caps? Should I just take it a tech?

 

[6L6C]

I’m not a tech either; just know enough to be dangerous. :shock:
But yeah I would take it to a tech because one of the problems you described can kind of tie into bad caps.
The caps in question would be the electrolytic capacitors there are I think 6 or 7 in the Mark IV.
You might want to do some searches on the forum about the subject.

Basically you will run into two types of people:
People who change them out every 8-10 years no matter what, like me and people who don’t believe in changing them unless there is a physical problem such as leaking or bulging or just plain exploded.

Have a few links that should get your feet wet.


http://forum.grailtone.com/viewtopic.php?t=25419&highlight=electrolytic
http://forum.grailtone.com/viewtopic.php?t=21337&highlight=electrolytic
http://forum.grailtone.com/viewtopic.php?t=9243&highlight=electrolytic

http://forum.grailtone.com/viewtopic.php?t=25896&highlight=cap+job
http://forum.grailtone.com/viewtopic.php?t=24700&highlight=cap+job

 

[JOEY B.]

If you have done a complete retube with new tubes, I would then suggest taking a guitar cable, spraying some contact cleaner onto the cable end, insert it into the input, effects send, and effects return jack. Once you get the cable inserted into each jack, twist it back and forth. This will clean the contact area of each jack. The first MkIV that I bought (used) did the same thing. If someone has left a cable plugged into the input jack for years, you might have to go inside the amp to establish a good connection (usually to correct the ground when the cable is removed).

 

[Buddy]

Do just as Joey B. suggests , and take it from there .

Could be the dirty pot syndrome also .. slightly more complicated .

But carefully done , very rewarding .

 

[Killtone]

Thanks for all of the information. I really appreciate it.

I bought the amp new about 14 years ago, so maybe it is time for new caps. I'll try the contact cleaner thing too, although it has never sat for more that a couple of days with a plug in it. I have gigged with it pretty consistantly for the last 5 years and it rides in the back of an equipment trailer (in a ATA case) so it probably takes a little bit of jarring.

Thanks again for the info.