Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Willabe on March 18, 2014, 12:34:02 pm
-
I started this in Jan. 2013. :laugh:
I have gone through many revisions in the layout and will go with what I have. There is no perfect layout no matter how you slice and dice it.
Chassis, face/back plates are drilled and eyelet/turret board is finished.
Made a mistake on the eyelet/turret board and input jacks. I'm going to cut the end of the board off and all should be good. :BangHead:
Here's some pics.
Brad :icon_biggrin:
-
Way cool my friend. Did you finally get the OT specs? I got to play one if these babys in Johnson City Tennessee and man is it nice.
Keep those photos coming. BTW, I never asked, do you like blue? :icon_biggrin:
-
cool stuff
-
Thanks guys. Yes blue is my favorite color. :laugh:
I bought a 2'x3'x1/8" (I've been using the standard yellow in 1/16" till now) sheet of the blue garolite from McMaster/Carr. It seems to not scratch but scuff pretty easy so I'm not thrilled with it at this point. I'm using diamond tile blades to cut it on my table saw and miter box. Their 7" and $7 to $20 each from a big box store they work real good so far. I did buy 1 that was a thin 1 and it heated up and got the - wonky wobble - going, not good as I was cutting 1/16" at a slow feed. I threw it out. I've seen cheap, thin blades do that before cutting thick wood stock. It's dangerous and can cause the saw to kick/throw the stock. Surprisingly if you get the stock out and keep running the saw to cool the blade it straightens/flattens right out again but I don't trust them after that. That much heat softens the steel. We only kept using them in a pinch at work if we didn't have a spare new blade and only on tear outs or for rough cuts. Threw them out at the end of the day.
No I still haven't got the OT specs maybe some day.
I think the amp you played is an older 1 and has 7 tubes instead of 6 and has an octal or 2 in the lineup. Gibson had flooded years ago and lost some of their schematics and I think that model is 1 they lost. I've seen them on ebay and it's listed in the Gibson amp book I have.
More pics.
Brad :icon_biggrin:
-
GREAT pics!! :thumbsup:
Keep 'em coming. I've been looking forward to seeing this come together, and I can't wait to hear a little clip.
Makes me want to start drilling holes...... :icon_biggrin:....and that's never a bad thing
-
Fine looking project. I posted the same, yesterday, but for some reason it didn't take. Anyway, enjoying the pictures and looking forward to more.
Jack
-
Looks like you may have drilled the faceplate and chassis at the same time. I finally found a way to do cheap faceplates that look pro. I get a partner sign shop to print the faceplate directly to 0.24 and then laminate the face.
Attach to the edges with rivets where you will not see them when in the cab. Punch away, works great. I can do color too.
Like your progress so far. Keep em coming
-
Thanks guys.
Dave, it'll be a while before I can get a clip but I guess I should do a little something.
Jack the forums new server had been giving Doug some problems yesterday. Try reposting it should be fine now.
Ed, yes I did drill the face plates taped to the chassis. It has been working great as long as I put a piece of blue painters tape on the vinyl face plate so it doesn't get scratch from the curly Al ribbons coming off the drill bit. I don't trust this vinyl sign material to last without scratching. It looks good now but..... :think1:
I've been getting the plates at a engraver that makes desk/door/hallway signs, awards/trophies and badges, stuff like that.
What is this 0.24 material? That's almost a 1/4", maybe you meant 0.024?
Steel? Al? Is it silk screened?
Brad :icon_biggrin:
-
Brad -
Which 77 did you model yours after? That was one of the questions that I asked, that didn't get posted the first time around.
Jack
-
It's this 1 Jack;
http://el34world.com/charts/Schematics/files/gibson/Gibson_GA-77.pdf (http://el34world.com/charts/Schematics/files/gibson/Gibson_GA-77.pdf)
The early 1's had a 7 tube lineup with an octal or 2.
The later GA-70/GA-77 are the same amp just different names. They have a 6 tube lineup with a 12AY7, 12AX7 and a 12AU7. The GA-70 (or was it vice versa?) was covered in a western motif. Gibson did things to their amps without releasing a schemo with the changes at times. I've seen some GA-70/77 with no presence control and some (GA-77) without the single - tone - control, which is a 5E3 type tone control. They came with a 15" Jensen.
The later 1's are VERY close to a Fender tweed Bassman 5E5a (and a couple other tweed amps) just different tone stacks, Gibby has no FB around the 2nd stage and different 12 _ _ 7 tubes.
http://el34world.com/charts/Schematics/files/fender/Fender_BASSMAN_5E6A.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_BASSMAN_5E6A.pdf)
I'll post my schematic in a day or 2. I added a little B+ filtering and added a PPIMV. Other wise pretty much stock. I'm not a big gain guy.
Brad :icon_biggrin:
-
Looks great!
This is the best Gibson amp site I've come across, is there a better one?
http://www.0rigami.com/gg/amps.html (http://www.0rigami.com/gg/amps.html)
-
This is the best Gibson amp site I've come across, is there a better one?
http://www.0rigami.com/gg/amps.html (http://www.0rigami.com/gg/amps.html)
Thanks for that link! Lotta info.