Mark IV C411 mod

hi,

just discovered that last stage of pre amp is EQ transistor cascade stage , and signal path through it, EQ used or not !

at the output of this stage these is a coupling cap , not a life time sprague film one, but an electrolytic 1uf , at this small value this part last not so great along the time as it could be dry (it is not automatic) , so when people recap filter big blue ones, they should get a look at this C411, if its a electrolytic !

i personnally would drop in a 715p 400v sprague 1uf, as all the signal chain is prop film why changing?

it brough for me this amp some life back!

enjoy

c411 is not 1uf but .1uf,unless the schem has a typo.It is an electrolytic because if you look,it is filtering a neg voltage supply,as is c412 at the other end,but 412 is 10uf.While it is proper to change these with a re-cap,I would use the electro here.

stokes said:

c411 is not 1uf but .1uf,unless the schem has a typo.It is an electrolytic because if you look,it is filtering a neg voltage supply,as is c412 at the other end,but 412 is 10uf.While it is proper to change these with a re-cap,I would use the electro here.

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nope, mine is a 1uf lytic orange sprague

another filtering neg eq rail lytic here? where? and why?
thx but no need help .




here its a blue lytic, arrows

Okay,like I said it could be a typo on my schem,But its still an electro,connected reverse to a neg voltage.Why do you suppose some engineer designed it with an electro?Could that be a typo?Perhaps they should have consulted you.

stokes said:

Okay,like I said it could be a typo on my schem,But its still an electro,connected reverse to a neg voltage.Why do you suppose some engineer designed it with an electro?Could that be a typo?Perhaps they should have consulted you.

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coupling here sprague 1uf not a 100nf, not filtering cap !
just talking about facts, and what i find,
not shoulda woulda coulda dreams !

even the IVb has it

http://www.amparchives.com/Amp%20Archives/Mesa%20Engineering/Schematics/Mesa%20Boogie%20Mark%20IVB%20Schematics.pdf

Whats your problem?