Gibson GA-40
Posted: Sun Jun 20, 2010 6:03 am
Have any of you guys messed with one of these? My friend's brother has owned a '54 GA-40 "Les Paul" amp for about 30 years. It hasn't worked since he got it, and has been sitting in a closet ever since. He was over a while ago, and when he saw my homebuilt amp collection, asked if I'd look at it. It played, but had a nasty, spitty fizz type tone that would die off immediately after playing. I fired up the trusty fluke, and started checking impedance and voltage.
This thing is like a rats nest inside, and the ONLY documentation I could find for this thing was a schematic that looked like the amp sounded..... After a few hours of trying to figure out what was what (now I KNOW why Dave Reeves built Hiwatts the way he did...... He probably cut his teeth on amps like this!). Troubleshooting a Hiwatt is childs play compared to this thing.
After reading up on these things, most guys say just to replace pretty much all the caps, so I did. They were mostly those wax dipped jobs. I put in a mix of stuff I had lying around. I also picked up some new tubes, all NOS except the 6V6s and the PI, which is a 6sn7.
Anyway, I found a few dead resistors and some way out of spec ones. I replaced them and it fired right up. I didn't have a chance to mess with it much, but it sounded great at low to medium volume, and the tremelo even works! Tomorrow, it's getting cranked.
He's gonna be so happy that this thing works again. The guy is short on cash, and didn't want to spend a ton on it. I actually owe my friend (his brother) a favor or 2, so I am not even gonna charge him for the parts I replaced.
I gotta get some pics with my R4.......
This thing is like a rats nest inside, and the ONLY documentation I could find for this thing was a schematic that looked like the amp sounded..... After a few hours of trying to figure out what was what (now I KNOW why Dave Reeves built Hiwatts the way he did...... He probably cut his teeth on amps like this!). Troubleshooting a Hiwatt is childs play compared to this thing.
After reading up on these things, most guys say just to replace pretty much all the caps, so I did. They were mostly those wax dipped jobs. I put in a mix of stuff I had lying around. I also picked up some new tubes, all NOS except the 6V6s and the PI, which is a 6sn7.
Anyway, I found a few dead resistors and some way out of spec ones. I replaced them and it fired right up. I didn't have a chance to mess with it much, but it sounded great at low to medium volume, and the tremelo even works! Tomorrow, it's getting cranked.
He's gonna be so happy that this thing works again. The guy is short on cash, and didn't want to spend a ton on it. I actually owe my friend (his brother) a favor or 2, so I am not even gonna charge him for the parts I replaced.
I gotta get some pics with my R4.......
