reverb in mark 4

[billyg121]

i am having problems with my reverb on my mark 4.when i turn the reverb knob anywhere beyond zero...my tone completly changes.it gets very tinny and high pitched.could this be the reverb acttually going bad?any suggestions?thanks

 

[Platypus]

Sounds like possibly a bad preamp tube. Check your manual for which tube controls the reverb, I want to say V4 but def. check.

 

[Restless Rocks]

In the Mark IVA, V4 is responsible for both reverb driver and return amp.
In the Mark IVB V4b is the reverb driver and V3b is the reverb return amp. V4a and V3a are used by the lead ch circuit. Also check to see if your reverb tank connections are plugged in well. Good Luck!

 

[Bullen]

Also, the A version uses a 12at7 (ECC81) tube for reverb, the B uses a 12ax7 (ECC83).