mk iii reverb..

[Shep]

so first the tank dies.. i replace it with a a old fender tank i had lying around.. i had to earth the input cable for it to work..something with fender tank's.. it's worked and sound REALLY fat and juicy.. then a few week's later i was playing my amp and it went into microphonic's and it turned out to be the reverb tube.. i replaced the tube turned it on and all was good.. i turned the reverb down because i don't really use it to much and the amp worked great..

now today i was playing it and after a while i turned the verb up and that squeally sound come out again.. so i thought that it blew another tube.. i changed it and fired her up and everything seemed ok.. until after a min or so of playing it started to do it again...


I know it's NOT the tubes... it works for about 60 seconds then it will start to crackle and squeal... it's very weird...

I am thinking one of the supply cap's or something has gone so when it heats up it fails and puts way to much into the tube causing it to go into mircophonic's.. does this sound like a possible reason..?

Any idea's?

i am pulling her apart tonight..

thanks All

Tom

 

[Boogiebabies]

Check the 100K V4A plate load resistor. The III uses a 1/2 watt instead of the 2 watt like older versions and it could blow out easier leading to clpping or squealing of the reverb output circuit . Also, if the impedence of the reverb tank is wrong it may blow the tiny transformers in the tank or is putting the wrong load on the reverb transformer.

 

[JimAnsell]

if you solder a lead between the in and out of the reverb cables going into the chassis, does it make the reverb stronger?

mike b did that on one of my old c+'s, along with a resistor swap and it made the verb stronger.

 

[Shep]

i was talking to my 'New' friend Mr Gerald weber..yes The Mr weber..and he agree with me on the bad joint idea and suggested the chop stick method..

BB i checked that 100k cold and it was good BUT i am going to fire her up and then test things alitle warmer for heat related value drift.. i think things will start to show it's self then...


Thanks Tom

 

[Boogiebabies]

Chinese sounds good.

I met Gerald at a guitar show. He looked like Chewbacca, but you could see his smile. I have read his column in Vintage Guitar for years and he is a wealth of knowledge.

 

[Shep]

Chinese sounds good.

I met Gerald at a guitar show. He looked like Chewbacca, but you could see his smile. I have read his column in Vintage Guitar for years and he is a wealth of knowledge.

?????

I have only talk to him over the net..

huge amount of knowledge..very clever guy..