Mark IIB Problem.

[BPski]

OK, I did the Reverb jumper mod/repair. The static or rattle sound is still there. I also tried the amp with the chassis in its cabinet with the Reverb wires disconnected. I may have to make this amp into a head! Any other ideas gentlemen?? Thank you!!!!

 

[stokes]

I asume removing the rev.cables with the chassis in the cab didnt solve anything.I am also going to assume when the chassis is out of the cab you are using the cab as the speaker and dont get the rattle.Do you have another spkr cab?If so try the ext. cab with the chassis in the combo cab,that way you can eliminate something in the combo cab,if you get the symptom thru the ext.cab.If you crank the clean channel full tilt do you get the rattle?Or are you certain it is limited to only the lead channel?

 

[Boogiebabies]

It could be plain old power tube rattle.

 

[stokes]

That was where I was going with trying the clean channel full out.It should appear with the volume full blast.

 

[BPski]

I have tried a different cab with different speaker. I have tried the clean channel with Volume on 10 and Master over 5-6 and the static rattle is not there. It is in the Lead channel and is not there when the Lead Master is set at low volumes (like under 2). Could it be a bad coupling cap in the Lead channel?

Also to note I said before I heard a similar noise in a BF Fender amp a few years back and it was a bad cathode bypass cap. The ones in my amp are tantalum not electrolytic which last virtually forever. Any experience with tantalums going bad?

I have a 100w version of this problem amp. It is about 75 serial numbers apart and the circuitry and wiring is about identical except for the power tube/phase inverter board naturally. That amp plays steady as a rock. The amp with the problem has a certain mojo-tone to it though. I have to fix this!!!! Thanks again!!!!!!!!!!

 

[stokes]

You could check to see if there is dc voltage on the lead master pot.That would indicat the cap from pin 6 on v3 is leaky.If it is it could cause the symptoms you describe.

 

[Boogiebabies]

I have seen a few Mesa's that Mike B. replaced all the cathode caps.
Maybe there is something to it.

 

[BPski]

I will check to see if there is dc on the Lead Master pot and replace the cathode bypass caps in the Lead circuit. I just happen to have some.

We should all just play through tweed Deluxe's and call it a day. A handful-and-a-half of parts and tone from here to Dixe and back. Simple as heck to fix (or build) and if you use 3-4 of them it is like a wall.

Oh well back to the Mesa bench. I'll check in with y'all later or tomorrow. I have trick or treater's to deal with. My town does it today so they can have the Halloween parade on the 31st to rake in some more revenue!!! Thank you!!!!

 

[stokes]

I'm with you on that Deluxe-got two of them myself.

 

[BPski]

Ok, so I think I figured this static/rattle noise is. I had a problem with the Pull Bright on the Lead Master on another IIB I had a while back. I took apart the switch on that pot and cleaned it. Problem cured. This time I think it is the Pull Lead switch. I will clean both Pull Bright and Pull Lead and post results.

The Reverb mod actually did help the Reverb. Before the mod it sounded like Dick Dale (who I think is awesome) on like1- 2. Now there is a more gradual progression of Reverb. Nice. I just thought it was the tank.

I will return. Thank you!!!!!

 

[RR]

I'm with you on that Deluxe-got two of them myself.

Bad *** blues amps ... I'm getting an Allen Kit Accomplice version of Fender's Deluxe.

 

[BPski]

I think I have this amp fixed. I literally took apart the Lead Drive and Lead Master pots and cleaned the switching contacts. The amp has not made that static/rattle sound yet. Go figure! Anyway thanks for all the help!

 

[stokes]

Glad to hear you got to the bottom of it.I would replace the pots.Probably a bad contact in the switch, vibrations from the cab might loosen it up again.

 

[BPski]

I think it was the Pull Lead function of the Lead Drive pot. Although if this contact was faulty wouldn't the relay chatter or something? The relay never switched or "chattered". I just got that static/rattle sound through the speaker. I do not know what the deal was all I know is that it seems to be behaving now. Amen. Thanks again for all the support and ideas.

 

[stokes]

If it wasnt actually breaking contact,just kind of loose I would think it could cause just a rattle or static sound with the vibration.Who knows,at least its acting okay now.