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andrew riddle
Posted on Thursday, January 27, 2005 - 09:20 am:   

i've got a 112-sixty five w/ the 12AX7A tube, and recently when i play through the effects channel i get significantly less power/volume than when i play through the dry channel at the same volume settings. i'm wondering what could be causing this, i know very little about amp electronics. hope someone can help.

also, the speaker in it is rated at 90 watts max, does this matter (ie, is it better to have a speaker rated closer to the amps 65W output?)

thanks!
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michael kaus
Posted on Friday, January 28, 2005 - 06:55 am:   

Sounds like you either have one side of the preamp going south or something as simple as a crappy input jack. I've seen my own 210-65 have real low volume on the reverb side and theinput jack was getting cruddy. Sounds too easy but it will do it. Use some de-oxit or something like it on the jacks-out of the case if possible and move it in and out with a plug and try it. do the same with the output while you have them out. It's 30 yrs old and could use some de gunking. If that doesn't clear it up, I would say the front end is weak. MIke.
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Thurston
Posted on Friday, February 04, 2005 - 11:31 am:   

I think I'm having the same problem with my Sixty-Five head. I had been using the bass channel with my guitar on lower volume settings for a while. I went to jam with some friends, and noticed that I had to run the master volume at 8-9 to keep up with the drummer. When I switched to the guitar channel, My head was almost blown off by the volume coming out
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John Drexler
Posted on Friday, February 04, 2005 - 04:31 pm:   

If it turns out to be a bad Output Transformer, I highly recommend getting the 3-65 replacement from Mojotone.com. Ask for Andy Turner. They sell Heyboer wound trannys, and I just put one in my 112-65, and it is absolutely great! Gave me back about 30% more volume. I set the master on 5 instead of 7 now to get the same volume...but it's cleaner and tighter now.
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andrew riddle
Posted on Thursday, February 17, 2005 - 01:15 pm:   

problem solved. i didn't exactly understand the tech talk, but i belive my problem was a leaking op amp or chip of some sort. looked like a little silver asprin with 8 or ten legs and cost less than 2 bucks. please excuse my rudimentary understanding of these things. my 112 sounds better than it ever has since i bought it and it is louder than holy hell. i had no idea.
thanks for the suggestions!
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cerebralsugar
Posted on Thursday, February 17, 2005 - 01:46 pm:   

What did you use for the new chip?
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andrew riddle
Posted on Saturday, February 19, 2005 - 12:48 pm:   

From the horses mouth:

"Your user group should know that the LM307H opamp used in the first gain
preamp stage can become leaky, resulting in lower volume and lack of
frequency response. I have a limited number of these opamps from when I was
an authorized MusicMan service center.
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michael kaus
Posted on Saturday, February 19, 2005 - 04:27 pm:   

let me know where he got them. I would like to stock a couple. Mike

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