[Jack Gifford]

Quite some time ago a forums member wanted to see a picture of the amp I built in 1959 (as transistors were getting more common) and am still using. I declined, since the grill cloth is deteriorated. But what the heck... as winter boredom starts to set in I snapped a couple of photos. The basic electronics course of my General Electric college-level apprentice program allowed us one "personal" project, so I chose an audio amp circuit that uses two power transistors in a class-B push/pull configuration- good for a clean 10 watts RMS. I built the aluminum chassis during my time in the apprentice tool and die shop. I've used it mostly where there's no AC power, by strapping a motorcycle battery into it. These days it mostly collects dust in the garage, since my hands shake too badly to make any decent music.

[dataway]

I would love to see the schematic for that ... in the late 60's I bought one of the first affordable mass produced solid state amps ... a 100w Jordon ( long since out of business).

Would be a fun project to try to replicate your amp.

I've played my whole life ... and just this last year arthritis seems to be rearing it's ugly head. So far I'm still fine if I take Ibuprofen before playing ... I'm sure it's not going to get any better.

Sorry to hear you can't play anymore ... but thanks for the photos.

PS. Your shop looks a comfortable, inviting place that would be relaxing to hang out in.

[F ROCK]

nice!

[Half-Inch Stud]

GE....worked there too.

Nice amplifier because as you know 10 Watts can be mighty loud for a guitar, & you know what it is made of.
I enjoy making the output stage. Its the darn preamps i dont like making.

My hobby uses tubes, whereas the 70s-80 saw some transistor efforts ( kept blowing out the bjts). FETs came along but never built the FET audio...too close to feeling like work.


Perhaps you clean the amp up, and just noodle about on the guitar; supposed to be good for the brain.

[TAKerry]

That's pretty cool. I used to play but my son has taken over my gear and lives and breathes the stuff. I will show this to him.

[bird72]

Very cool, Jack! Tell us about guitar. Melody Maker?

[vertigto]

Very cool.

Big tube snob myself, but appreciate the design and effort to create...nice job!

[Jack Gifford]

A cheap Gibson Melody Maker, that I don't mind leaving out in the poor atmosphere of the garage- fumes, dust, etc. Unlike the Gretsch "Monkees" axe and Gibson Explorer tube amp that I take better care of.

[tom s]

Jack,left you a phone message!Tom

[Jack Gifford]

Thanks Tom. I saw it too late to call back. I'll try to remember tomorrow.

[Brian Baker]

Nice !!! I had no idea you were a picker from way back. Been playing for 37 years myself.

[dataway]

Jack, you don't still have the schematic for that amp do you? I've been hankering to do an electronics project lately.

[Keith Seymore]

Originally Posted by dataway

PS. Your shop looks a comfortable, inviting place that would be relaxing to hang out in.

Agree - it looks "warm" (in the inviting sense, not necessarily the temperature sense).

Fender has a big display in our lobby this week. Guitars (acoustic and electric), amps and a make believe stage, along with crates and comfy seating.

K

[Jack Gifford]

Mongo- pickin' since about 1954. That's what, 65 years? Irritates me that I'm losing the "touch".

dataway- I'm sure the schematic is around here somewhere. I'll look for it. But you would need to engineer substitutes for obsolete 2N255 transistors, etc.

Keith- Is there an antique Fender "Blonde" tube amp in the display? I had one for awhile that I liked. It was fairly small but had really strong tenor response- piercing if desired!

[Jack Gifford]

Just remembered that I had a really beat up old acoustic flat-top guitar in 1951 that I learned to play "Wildwood Flower" on. So about 68 years of pickin' for me!

[Half-Inch Stud]

npn 2N3055 will do anything

but your pnp may play with a mj2955

[Jack Gifford]

I hope this image of the schematic is readable.
I seem to remember changing to a screwdriver-adjust pot in the biasing of the two output transistors to be able to prevent thermal runaway. They do need substantial heatsinks- I used 3" square aluminum.

[Half-Inch Stud]

Ha! those GE notepads are priceless! I still use them.

T1 was key to smooth performance and operation. You could put any "40W or 90W" pnp & npn pair in that output and it should play.

[dataway]

Originally Posted by Jack Gifford

I hope this image of the schematic is readable.
I seem to remember changing to a screwdriver-adjust pot in the biasing of the two output transistors to be able to prevent thermal runaway. They do need substantial heatsinks- I used 3" square aluminum.

That will work as a start ... love the notation for labeling the E,B,C on the power transistor.

And in 1968 when I started playing at 10 years old ... wildwood flower was one of the first songs, I still have the hand written music from my teacher some 50+ years ago.

[Half-Inch Stud]

Oops, they are all pnps