I bought this '61 Gibson GA30RV on eBay back in May; it's been messing with me a little but I've got most of the bugs straightened out. In the '59-'62 Gibson tweed era, Gibson made their first three reverb amps; the GA19RVT (12" speaker, reverb, tremolo), the GA77 (6L6s, 15" speaker), and this GA30RV. The amp has twin 6V6s, 5Y3 rectifier, a choke, three 6EU7s in the preamp, a 12AU7 for reverb recovery/phase inverter, and 12" and 8" speakers.
It was delivered with a silver-frame 8" C8S and a 12" C12R ceramic speaker labeled 'Thomas Organ High Fidelity'.
As-delivered C12R on the left; replacement '60 Jensen P12N on the right; re-coned and with a new voice coil ... Thanks again Valcotone!
I don't think the silver-frame 8" Jensen is original; delivered speaker on the left and an authentic original C8S on the right ... although it hardly matters; the original 8" speakers never had enough substance to withstand hard play. As delivered, both speakers had torn speaker cones ... a fact which the seller failed to mention :evil: :
Although sort of new, it got new caps anyway (more on the caps below):
The tube deck after getting cleaned with Flitz metal polish:
And the transformer deck after getting Flitzed:
The control panel has some corrosion but most of the silk-screen is intact. Acrylic handle insert with original fabric courtesy of Wuzzatronics Sound Labs NZ ... these handles/inserts have all but vanished.
The vertical-mount reverb can and footswitch; can has a piece of foam underneath that stabilizes the springs when the handle is put in the travel position. (Wire in bag at left edge of pic courtesy of PhillySteve'Zamps; very high grade tinned hookup wire):
Web-lore has it that these mahogany footswitches were originally made from the scrap of mahogany left after making the cut-away on Les Paul bodies. FS below attached to member BluesDan's Gibson GA18. New FS will get sanded and a coat of Min-wax's Bombay Mahogany ... color is a near-perfect match:
When I took the back off the amp, it had one too many electrolytic filter caps ... and not just an un-needed extra, the cap labeled 'A' below is connected where it's supposed to be except it's 100uf :shock: ... not 20uf as called for on the schematic and on the 5Y3 tube data sheet. The cap labeled 'B' is mindlessly connected to the other heater connection on the rectifier - it's not doing anything ... seller said 'mustta been my tech' ...
The pic in the upper left shows that the 4.7K / 1 watt resistor was missing; pic on upper right shows it in place. Also, instead of a 6.8K / 1 watt resistor, the amp had a 2.2K / 1 watt; I don't know if this is just unit-to-unit variation from on-the-fly changes or the effects of cowboys in the power supply. Has (the right number/value of) new caps and the B+ rail produces voltages per the schematic.
In praise of Gibson; there are thing a lot of people wish they'd done: used better output transformers, jacked/not hard-wired speakers and footswitches (the reverb footswitch in this amp is hard-wired to the end of the reverb can) and some other stuff but they had a useful fetish about grounding.
The green arrows below indicate the puddle grounds on the chassis where brought and soldered a ground wire from the preamp tube sockets. The red arrows indicate the rubber vibration-damping grommets they trapped under the rivets used to hold the sockets to the chassis. They went out of their way to take steps to mitigate microphonics ... a chronic source of shortened useful tube life.
Almost done: the 8" Celestion G8L on the left also courtesy of Wuzzatronics Sound Labs NZ in exchange for tools and parts. Runs very well and sounds like it's supposed; warm and fat and pure Gibson. With the larger speaker magnets and the choke, the amp holds on until 7/8 before it starts to break up ... that's pretty late for most 6V6/class B push-pull amps.
The amp still needs a tone control and/or tone cap; with bass rolled off, don't get much twangy out of it. I also rebuilt the output section downstream of the phase inverter; .02 uf / Mallory 150 coupling caps, 220K grid bias resistors, and a new 6V6 cathode bias resistor and bypass cap; blew the first replacement bypass cap out (installed backwards?) and made the tubes glow blue and the rectifier bright orange ... :shock: :shock: Not good.
The links below were lifted out of a thread on the Gear Page; together they make up a promotional film done by Mullard; the legendary UK maker of vacuum tubes. Not a lot of tube theory or anything but the vids convey that, despite all kinds of automation, making/assembling tubes is almost as labor-intensive as it is tool-intensive. With the emergence of the transistor, a lot of Mullard's as well as US tube-making tooling was sold to eastern European countries; Yugoslavia, Hungary, among others.
http://www.youtube.com/watch?v=xnvKCC6_VDQ
http://www.youtube.com/watch?v=qSDDNg4Zb3w
http://www.youtube.com/watch?v=8ztjI4geVRA
http://www.youtube.com/watch?v=wDgOuI-RzgY
http://www.youtube.com/watch?v=1qMvhxo6B84
http://www.youtube.com/watch?v=Cyt9VvIzhSY
It was delivered with a silver-frame 8" C8S and a 12" C12R ceramic speaker labeled 'Thomas Organ High Fidelity'.
As-delivered C12R on the left; replacement '60 Jensen P12N on the right; re-coned and with a new voice coil ... Thanks again Valcotone!
I don't think the silver-frame 8" Jensen is original; delivered speaker on the left and an authentic original C8S on the right ... although it hardly matters; the original 8" speakers never had enough substance to withstand hard play. As delivered, both speakers had torn speaker cones ... a fact which the seller failed to mention :evil: :
Although sort of new, it got new caps anyway (more on the caps below):
The tube deck after getting cleaned with Flitz metal polish:
And the transformer deck after getting Flitzed:
The control panel has some corrosion but most of the silk-screen is intact. Acrylic handle insert with original fabric courtesy of Wuzzatronics Sound Labs NZ ... these handles/inserts have all but vanished.
The vertical-mount reverb can and footswitch; can has a piece of foam underneath that stabilizes the springs when the handle is put in the travel position. (Wire in bag at left edge of pic courtesy of PhillySteve'Zamps; very high grade tinned hookup wire):
Web-lore has it that these mahogany footswitches were originally made from the scrap of mahogany left after making the cut-away on Les Paul bodies. FS below attached to member BluesDan's Gibson GA18. New FS will get sanded and a coat of Min-wax's Bombay Mahogany ... color is a near-perfect match:
When I took the back off the amp, it had one too many electrolytic filter caps ... and not just an un-needed extra, the cap labeled 'A' below is connected where it's supposed to be except it's 100uf :shock: ... not 20uf as called for on the schematic and on the 5Y3 tube data sheet. The cap labeled 'B' is mindlessly connected to the other heater connection on the rectifier - it's not doing anything ... seller said 'mustta been my tech' ...
The pic in the upper left shows that the 4.7K / 1 watt resistor was missing; pic on upper right shows it in place. Also, instead of a 6.8K / 1 watt resistor, the amp had a 2.2K / 1 watt; I don't know if this is just unit-to-unit variation from on-the-fly changes or the effects of cowboys in the power supply. Has (the right number/value of) new caps and the B+ rail produces voltages per the schematic.
In praise of Gibson; there are thing a lot of people wish they'd done: used better output transformers, jacked/not hard-wired speakers and footswitches (the reverb footswitch in this amp is hard-wired to the end of the reverb can) and some other stuff but they had a useful fetish about grounding.
The green arrows below indicate the puddle grounds on the chassis where brought and soldered a ground wire from the preamp tube sockets. The red arrows indicate the rubber vibration-damping grommets they trapped under the rivets used to hold the sockets to the chassis. They went out of their way to take steps to mitigate microphonics ... a chronic source of shortened useful tube life.
Almost done: the 8" Celestion G8L on the left also courtesy of Wuzzatronics Sound Labs NZ in exchange for tools and parts. Runs very well and sounds like it's supposed; warm and fat and pure Gibson. With the larger speaker magnets and the choke, the amp holds on until 7/8 before it starts to break up ... that's pretty late for most 6V6/class B push-pull amps.
The amp still needs a tone control and/or tone cap; with bass rolled off, don't get much twangy out of it. I also rebuilt the output section downstream of the phase inverter; .02 uf / Mallory 150 coupling caps, 220K grid bias resistors, and a new 6V6 cathode bias resistor and bypass cap; blew the first replacement bypass cap out (installed backwards?) and made the tubes glow blue and the rectifier bright orange ... :shock: :shock: Not good.
The links below were lifted out of a thread on the Gear Page; together they make up a promotional film done by Mullard; the legendary UK maker of vacuum tubes. Not a lot of tube theory or anything but the vids convey that, despite all kinds of automation, making/assembling tubes is almost as labor-intensive as it is tool-intensive. With the emergence of the transistor, a lot of Mullard's as well as US tube-making tooling was sold to eastern European countries; Yugoslavia, Hungary, among others.
http://www.youtube.com/watch?v=xnvKCC6_VDQ
http://www.youtube.com/watch?v=qSDDNg4Zb3w
http://www.youtube.com/watch?v=8ztjI4geVRA
http://www.youtube.com/watch?v=wDgOuI-RzgY
http://www.youtube.com/watch?v=1qMvhxo6B84
http://www.youtube.com/watch?v=Cyt9VvIzhSY
