Monday, December 19, 2011
New Arrivals and A Project
A couple of new amps arrived here at mi ranchito for stays of indeterminate duration. One's a silver face Deluxe Reverb with the volume boost about which little need be said except that nobody ever uses the volume boost. It needs a little love in the form of a cleanup and a new vibrato roach which will be ordered this morning.
It remains to be seen whether I'll form a bond with it, although the Dragon Lady said "Oh. You can keep that if you like." Which was a big surprise, and it raises questions about whether I've got some kinda Stockholm Syndrome thing going on here but whatever-I'll take de job.
The second is far more interesting but enigmatic, and when I heard it had a 15 inch speaker I was hooked.
It's the Maestro M216 RVT pictured at left, and it's some sort of weirdo production from the Gibson works back in 1963 which was when it was made. The tube lineup is 5Y3-6V6-6V6-6EU7-6C4-6EU7-6EU7.
I've acquired it in a trade for a home brew consisting of a Motorola HS621 chassis mounted in an old Masco speaker cabinet with a 70w Eminence topping it off. It sounds surprisingly good and it appealed to the previous owner of the Maestro. The deal's done, and all that is needed to seal the deal is for me to hand over a couple of Franklins.
The circuit is unique and resembles only the GA19RVT Falcon in the Gibson Master Service Manual, but it is voiced differently-allegedly for accordion. It's single channel with swampy reverb and vibrato, but the amp just doesn't have enough volume. I spent most of Sunday afternoon trying different things to see if I could raise the volume level to acceptable levels-changing resistance values in strategic locations, installing a larger output transformer from a Deluxe Reverb, a solid state rectifier module and bypassing certain components to see whether the mystery could be unraveled.
All was in vain-even though I did find a resting place for one of my 1957 vintage Jensen P15R speakers. A general cleanup and chrome polish was had, and I subbed some Dakaware stove knobs because I just don't like those red pointers any. The knobs came from a tube tester I scrapped a while ago.
So, it seems I must study circuit design and topography to unravel this mystery. One clue that I have uncovered is that if the volume control is dimed, there is next to no white noise-which tells me something's rotten in Denmark.