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Vintage threads from the first ten years

Gibson Skylark GA-5

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9/14/1999 1:03 AM
TubeHead	Gibson Skylark GA-5 anyone know where a power tran for this little beast could be found? Every schem I have found shows 2 6V6 output tubes but this one has one preamp (12AU7) and two 6BQ5 (EL84's). thanx.

9/14/1999 4:44 PM

I don't know of an exact replacement, but this sounds very much like my 5AT ("T" for trem).

Probably an interstage tranny driving the EL84s if my guess is correct. If so, the first stage is one-half of the 12AU7, the second stage (interstage tranny driver) is the other half of the 12AU7. You can have some real fun by replacing the 12AU7 with a 12AT7, that thing will get up and wail for you if you do that.

Regarding tranny voltage: you need 308Vdc on the OT's center-tap, and basically it's just a silicon diode rectified f.w. rectified scheme to do that. PT: 220 - 0 - 220 @ greater-than or equal-to 70mA, 6.3Vac at greater-than or equal-to 2A for the heaters. Then just look for anything that'll physically fit somehow!

Best of luck,

Carl B.

9/14/1999 4:50 PM

Probably needs a filter-cap job, too.

Just figure on needing to replace the filter caps, mine sure needed that. Gibson sure didn't go with top-drawer filter caps.

And while you're at it, give it a decent speaker, like a Weber 10" with decent bass. I found a 10" old alnico that just makes mine the most fun-to-crank guitar amp ever. Talk about attitude!

(BTW, mine's a Skylark GA-5T, not a "5AT" like I posted above. Typing too fast.)

9/15/1999 5:39 AM

thanks Carl,

u'r exactly right. this amp does use an interstage

tranny driver, and the old wax looking filter caps

(dual 20uf/325 vdc) just look like replacing is a good idea.

thanks for the tip about a 12AT7 too! I am thinking a Hammond 263AX pwr tran might fill the bill here, only

think I want to investigate is why this orig. power tran

sounds like it is 'cooking' when powered up. Is that just

the way power trans do when they go bad or could this be

symptons of some other component(s) that are bad?

9/15/1999 1:18 PM
Doc	Leaking or shorted capacitors will draw excessive current through the power transformer, causing overheating and eventual failure. Replace all power supply caps BEFORE you use the amp. Then check operation. If the original power trans still makes noise and/or gets hot, the damage is already done.

9/15/1999 5:11 PM
Troy	Re: GA-5T Different Tubes I've got a friend's GA-5T right now with a blown speaker and in need of a complete cap job. This one has 1-6EU7, 1-6C4, and 2-EL84's, ss rectifier with that PP driver transformer. Carl or Doc, do you guys have any suggestions for this model? Troy

9/16/1999 5:08 AM
Bruce	Isn't that the one that Ken (Trainwreck) thinks is the coolest little Gibson ever made? Got your thing in the mail today Troy. Bruce

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