Mark 4 problems sueals when reverb volume is cut up

[LesPaulPlayer]

Just got a Mark 4 and having some issues when reverb volume is increased. Changed all pre amp tubes to Mesa and still problem. New to this amp so any help would be thankful

 

[Boogiebabies]

MK IV A or B ?

 

[LesPaulPlayer]

I'm new to these Mesa amps so how can you tell the differnce

 

[Boogiebabies]

B's have a stereo effects loops for the Satellite and a Sat send. Most have a removable power cable and a black powder coated
chassis instead of front and rear face plates. Serial numbers are usually below 6300 for A's. The IVA used a 12AT7 in the V4 for
reverb so I am wondering if you have a 12AX7 pushing the circuit too hard.

Either way, a bad ground at the jacks could cause distortion as well.

 

[LesPaulPlayer]

yea I have a 12xa7 in all the slots. When you say a bad ground where would the fix be at? Oh and I'm pretty sure that it's a "b"

 

[Boogiebabies]

Try cleaning the reverb jacks internally with contact cleaner. Also, check to make sure your tank is
hooked up properly.

 

[LesPaulPlayer]

Can you give me some in sight as to the correct way the tank should be hooked up correctley. Any pics would help. Also I did raise the springs in the reverb tank some and this seemed to have helped. So I'm guessing reverb chain is what is causing it to squeal. If you have it on chanel 3 with that master volume on about 5 and the amp volume say on 1.5 or 2 you can not raise the reverb volume past 2 or 3. Same way on channels 1 & 2 but you can get to 3 or 4 before you get a high pitch squeal. I do have 12AX7 in the reverb slot and they are brand new mesa tubes. Could power tubes cause any problems? I have 6L6 Winged C's in all 4 slots and I do notice a bluish tint to a couple of them.