2. amps-preamps
  3. 169899-137306

MC 240 ReTube or Replace

About a year and a half ago I acquired an old McIntosh MC 240.

I replaced the capacitors and retubed it using:

Genalex Gold Lion 12AU7 gol

Genalex Gold Lion 12AX7 gold

Tube Amp Doctor TAD 12BH7

TUNG-SOL 7581A

 

Now after some 1,000 hours of operation, driving a pair of Salk SS 6m speakers, one channel will intermittently give out a blast of static within minutes of power up and blows the fuse. This leads me to believe I have a tube which may be intermittently shorting.

 

With the MC 240 being almost 60 years old I’m wondering if modern technology has surpassed it.

Thus, the question retube or replace it.

 

Currently my choices are:

Quick Silver 60 watt mono amps

Mc Gary Audio SA 1

Van Alstine Vision SET 400

 

I would appreciate any comments.

TNX



pelletfan

Showing 5 responses by pelletfan

pelletfan OP
14 posts
 
Yup the power section was replaced with the capacitors.My older than dirt back will NOT allow me to lug around a 60 lb amp these days....
There are internal and external fuses which have randomly blown and to do a lot of further testing I'm going to need to get a lot more of each fuse.........
This is causing my pore ole back to complain!

pelletfan OP
14 posts
 
OK I swapped the output tubes side to side, reseated all the other tubes and replaced the internal b+ fuse.I powered it up and listened to it for 2 3/4 hours with no problems....
That has been it's history...  After 3 or so power ups .. a burst of static and a blown fuse.

We'll see what happens next :-(
pelletfan OP
14 posts
 
Thanks for the suggestion of lifts....I've used them over the years for several motorcycle builds :-)BUT you still have to get the amp onto the lift And THEY DON'T DO STAIRS WELL :-)
pelletfan OP
14 posts
 
As to the biasing I have resistors on hand and used such to achieve proper biasing.The amp has over 1000 hours on it with no other problems.
pelletfan OP
14 posts
 
For anyone following this it's been 2 weeks now with no problems.
So I'm thinking that I may have an intermittent loose connection on a tube socket.
I've also been thinking about the Quick Silver 60 watt mono amps which would give me less than 3dB, and the Mc Gary Audio SA 1 which has less power, of which neither will make an improvement in my system dynamically speaking.
More to discover