Gibson Skylark GA-5T

[CJ]

co-worker picked this up for 275 at the guitar show last weekend,

has a real nice crunch to it,

 

[CJ]

has some work done, filter caps, bypass cap, Jensen 8 ohm speaker,

the 470 K plate resistor for the 12AX7a preamp tube , first stage, was about 560 K, but we don't want to screw up the crunch, if it sounds good then leave it,

 

[rock soderstrom]

Wow, my favorite. 6BM8 version and killer tremolo.

 

[CJ]

i know Rock was foolin with a vol cntl for the vibrato a while back, don't know what the results were

 

[rock soderstrom]

I recently built a DIY version. I'm really looking forward to your thread and have already got the popcorn.

 

[rock soderstrom]

i am back to original atm. Amp needs a cabinet. Please show the OPT and its dimensions!

 

[CJ]

weird circuit 6BM8 has both vibrato tube and power tube combined,
m but not sure,
Sovtek makes a re-issue,

here are some voltages, i think this thing came with a 4 ohm,

luckily the heater voltage was 6.2, usually older amps have a problem with excessive heater voltsge due to increased mains voltages over the years,

somebody added two 100 ohm resistors off the heaters for a virtual CT and it seems to work good,

schemo>

 

[rock soderstrom]

weird circuit 6BM8 has both vibrato tube and power tube combined,
m but not sure,
Sovtek makes a re-issue,

It is the US equivalent to the ECL82, you can find tons of them in old r2r recorders. Nice tube!

 

[rock soderstrom]

here are some voltages, i think this thing came with a 4 ohm

Applause!

 

[CJ]

xfmr looks like a square stack of EI 50 just like Fender uses,

structure looks to be simple pri-sec,

EIA code 549 = Mid-West Coil & Transformer, Chi Town,

 

[CJ]

sq wave tests, unloaded sec,

 

[rock soderstrom]

xfmr looks like a square stack of EI 50 just like Fender uses,

structure looks to be simple pri-sec,

EIA code 549 = Mid-West Coil & Transformer, Chi Town,

Thanks a lot! I've been interested in this for a long time. There are virtually no GA5Ts on my side of the pond. Nice to see it here. Premium entertainment

 

[CJ]

flat at least to 100KC, first rez peak at 550 KC, a few smaller ones after that

 

[CJ]

cranking up the volume, speaker attached, secondary wave forms,

that notch down there on the second pic adds some hi end to the crunch,

 

[CJ]

output as much as i could get>

 

[rock soderstrom]

output as much as i could get>

Perfect!

 

[CJ]

Cabinet is about 13" x 13" x 7" slanted a bit,

 

[rock soderstrom]

Cabinet is about 13" x 13" x 7" slanted a bit,

Yes, really small. I've been playing my DIY GA-5T with a slightly bigger box so far. I've tried Jensen c10q and Jupiter 10SC, both work very well!

 

[CJ]

holy crap look at this guy,

 

[CJ]

somebody had a solid state rect plug in for the 5Y3, on the skylark, i did not notice much difference in sound so i put a 5y3 in there, reduced volts will be easier on the tube me thinks,