Swapping IC's on a SS 212 Sixty-Five

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Swapping IC's on a SS 212 Sixty-Five

Music Man Amps Discussion Forum » Adjustments, Maintenance & Calibration » Swapping IC's on a SS 212 Sixty-Five

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 Sean Borton (codamedia)
Username: codamedia
Registered: 03-2014
Posted on Tuesday, March 18, 2014 - 01:45 pm:   

This is on a 212 Sixty Five Chassis #2475-65
SS Phase Inverter. (from 1979)
I suspect I have a failing IC at the start of the normal channel (IC1). When I turn up the volume (on the normal channel) with nothing plugged in, I can hear some interference, yet when I turn up the Reverb / Vibrato channel - it is very quiet.
After reading a few other posts, it was suggested to move IC5 (reverb driver) to the IC1 position. How do you remove these IC's on the 2475-65? They are the circular LM307H but appear to be on a riser or socket... Do they pull out like the later models with standard looking chips - or do I have to unsolder them from the bottom?
 Mike Kaus (mm210)
Username: mm210
Registered: 05-2006
Posted on Tuesday, March 18, 2014 - 02:56 pm:   

They are in sockets. Pull gently. If they break, you will have a hell of a time finding replacements. Most people are using brown dog adapters and using contemporary 8 pin IC's with the socket adapters. Make SURE you orient yourself with HOW they go in the sockets(direction) Mike
 Sean (codamedia)
Username: codamedia
Registered: 03-2014
Posted on Tuesday, March 18, 2014 - 03:45 pm:   

Thanks for the info Mike.. I thought they were in a socket but didn't want to tug too hard until I new for sure...
Out of curiosity, are those TO-99 sockets?
 Mike Kaus (mm210)
Username: mm210
Registered: 05-2006
Posted on Wednesday, March 19, 2014 - 09:17 am:   

Yes.
Full Name
Sean
Music Man Equipment
1979 212 Sixty-Five, 1981 212 Seventy-Five
Numerous other amps and several guitars...

Member for

11 years 1 month

codamedia Fri, 05/09/2014 - 19:45

I finally opened up my amp again and tried the swap between IC1 (channel 1 pre-amp) and IC5 (reverb send).

Results = Really bad, and Really good... Not what I was expecting...

Channel one got really thin sounding to the point of unusable. On the other hand - the Reverb I always hated because is sounded so thin got really warm and inspiring. So this tells me IC5 was REALLY BAD while IC1 had a little added noise.

Does that mean I should look at replacing the IC's one by one? Or are the connections like tube sockets, where a little cleaning can go a long way? Sure, I can just try and see what happens (I'm sure it can't hurt, and I certainly intend to try) but I'm just checking to see what others have experienced.

Music Man Equipment
MM 2-10-65

Member for

11 years 1 month
Profile picture for user mm210

mm210 Sat, 05/10/2014 - 05:43

Just my opinion but I would jus try cleaning first because it costs NOTHING and I'm cheap! After that, I think I would PROBABLY invest in a few brown dog adapters and swap out the IC's with currently available units. The brown dog adapters will allow the use of updated ic's. If you want, here's a link to the OLD board with a GREAT discussion with Ed Goforth doing the hard work to get some answers.

http://www.pacair.com/discus/messages/22/593.html?1303540949

That would be MY tact at this point. Just my crappy opinion though. Mike.

Full Name
Sean
Music Man Equipment
1979 212 Sixty-Five, 1981 212 Seventy-Five
Numerous other amps and several guitars...

Member for

11 years 1 month

codamedia Sat, 05/10/2014 - 11:31

I'm thinking exactly the same thing... Never any harm in trying a good cleaning...

I'm going to order some brown dogs and sockets, that will open a few options down the road. ALSO - thanks for posting that link in this thread... I have read it before - but it' nice to have it accessible and in context...