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New MiniMax, No Dice

post #1 of 6
10/22/09 at 8:29pm
Thread Starter 
No sound at all. I haven't started troubleshooting yet, but thought someone might be able to pick something off from lolight oking at it.

Attachment 22010

Tubes light up, that's a good sign.

Center LED didn't light up on the first try, soldered in a new one, still no light. Kinda fubarred one of the pads (no longer existant) pulling the original LED out.

Not a drop of sound. No crackle, no pop,
LL
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post #2 of 6
10/22/09 at 9:04pm
Does relay ever kick in? Looks like the BD139 may be backwards.
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post #3 of 6
10/22/09 at 10:53pm
Thread Starter 
Quote:
Originally Posted by rhester View Post
Does relay ever kick in? Looks like the BD139 may be backwards.
Yesssss! Thank you. New miniMax is online.
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post #4 of 6
10/23/09 at 2:02am
Glad to hear it!

P.S. Thanks, Max - I've been out of town the last couple of days.
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post #5 of 6
10/23/09 at 1:52pm
Thread Starter 
Is it possible to get better than 14 gain out of this? It drives my HD515's like nobody's business, but my DT770's could use some more "umf".
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post #6 of 6
10/23/09 at 3:20pm
Quote:
Originally Posted by AGTCooke View Post
Is it possible to get better than 14 gain out of this? It drives my HD515's like nobody's business, but my DT770's could use some more "umf".
No. Except - there are 12AE6's and then there are 12AE6's. Some tubes have a naturally higher output than others. Testing can reveal some of this, but I've also had some low output tubes seemingly have more gain/slam than others.

Other than that, for high impedance cans, be sure that your bias is correctly adjusted for maximum voltage swing - that would be 1/2 the voltage supply setting (typically 13.5V for each tube). You should check that final bias about 3-4 hours after running. You may find that the bias drops by as much as a full volt, meaning you won't be getting the voltage swing you should.

Not sure that has as much or anything to do with it as do the tubes, though. There's a 12AJ6 that has the proper pinouts and voltages, but its gain is actually 55.(!) A couple of people have tried them and they didn't work in the circuit without constant clipping in the buffer. It might be worth a shot to try if you have a very weak source. No guarantees, though.
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