IIC+ Tune Up and Restoration- UPDATED

[gts]

Excellent picture tutorial Ed! Following it step by step, picture by picture, I bet that even I could do a cap job on a C+! ;-)

Now answer JB's questions will ya? (I'm curious too)

JB,

The recap tightened up the amp a good bit and the bottom end it pretty solid. Not a drastic change.
After the job my plate voltage only went down 2V, so those old caps were still functioning properly.
On old caps, as the ESR or effective series resistance goes up they tend to store, or as I say block more voltage.
I did one on a 60W and the old caps had the plates up to 474V and the amp sounded like a buzz saw and had no bottom end.
New caps brought it down to 448V.

I love that G-Flex, but the only reason it's used is because I am too lazy to carry up the Bogner 2X12.
Still enjoy blasting a C+ though the Mesa 4X12 too..... Just don't get to do it that often.

I know that assumption is the mother of all F-up's, but would an abnormally high plate voltage be a possible sign of capacitor degradation? Something to watch out for?

 

[stokes]

Dont mean to jump ahead of Ed's response to that question,but I will anyways.Plate voltage will change as power tubes get older because the current draw will change.If the current goes down,the voltage will go up,if the current rises the volts drop,so,to me,that isnt a good indicator.As Ed said earlier,the best test is to check the ESR.I was taught that after 10yrs or so the caps begin to degrade,so thats what I go with.Having had to clean up the mess an exploding cap causes,I dont like to wait.Some caps can last many years beyond that 10yr mark,but if you change them after 10 you will notice some improvement in response.Caps will actually last longer in an amp that sees a lot of use,when an amp sits unused for long periods the caps dry out from not having current flowing.I own a lot of amps,so they dont get used as often as they should.I try to get my sons to rotate them as they play way more than I do these days.But even still I turn them all on for a couple hours once a month to keep the caps flexed.

 

[fretout]

BB, thank you so much for posting your process of replacing caps! It's stuff like this that makes me really enjoy hanging out on this forum. It's the engineering side of me that loves to see how this stuff is done.

It's also a great reminder. I have a few amps that need some cap jobs...

 

[Boogiebabies]

JB,

The recap tightened up the amp a good bit and the bottom end it pretty solid. Not a drastic change.
After the job my plate voltage only went down 2V, so those old caps were still functioning properly.
On old caps, as the ESR or effective series resistance goes up they tend to store, or as I say block more voltage.
I did one on a 60W and the old caps had the plates up to 474V and the amp sounded like a buzz saw and had no bottom end.
New caps brought it down to 448V.

I love that G-Flex, but the only reason it's used is because I am too lazy to carry up the Bogner 2X12.
Still enjoy blasting a C+ though the Mesa 4X12 too..... Just don't get to do it that often.

I know that assumption is the mother of all F-up's, but would an abnormally high plate voltage be a possible sign of capacitor degradation? Something to watch out for?

You are 100% correct. Not so harmful on a 60W, but when a 60/100 or Simul starts pushing 515V with 117V at the wall the caps
are just waiting to blow. On your Simul's/100, 480V is normal, 60W are 448V and Export is 460V.

 

[Henz]

You are 100% correct. Not so harmful on a 60W, but when a 60/100 or Simul starts pushing 515V with 117V at the wall the caps
are just waiting to blow. On your Simul's/100, 480V is normal, 60W are 448V and Export is 460V.

Ty BB!! I just recapped my 1984 factory DRG C+ couple years ago. My plate voltages are 500+vdc a lot of times. My wall voltage is around 122V. What do you think happened? Ty!!! Jim