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Just picked this up a week or so ago. It's an Lectrolab R600, IDed by the schematic on the back; no other markings.
Dated tentatively by the speaker to 1955 (the photofact doc is dated 1957, but the schematic on the back looks older, too.)
Typical 6V6 PP output stage. Looks like grid-leak bias for the first stage. 12AY7 Preamp and PI --but not a lot of headroom. Has a very overdriven sound, think 50's Valco/Supro.
Has problems, of course. Fixed already: the OT was bumping up against the speaker (missing chassis screw)--that loosened the bolt which was also the GND for the can cap AND the shared 6V6 cathode bias resistor (check that out BTW--the loose resistor cover.) Those two issues sorted out--temp fix for the ground, and the bias resistor replaced with a nice 10 watter.
Now, it sounds good for 5 minutes. Then distortion begins--starts with a "creaking floor board" sound as the note decays, then gets progressively worse as the amp warms up.
NO--I haven't replaced the 12AY7's yet, just the 6V6's. I'll check downtown for new ones this week.
I'm not yet asking for input (although feel free to offer it), just wanted to document the amp, for which there are few photos on the interwebs... I thought yall might enjoy seeing this oddball old amp (and the great 60's contact paper...) Someone's missing their tablecloth, too. Also, under that nightmare the cab is cardboard, like some of those Dano amps. Half-inch thick cardboard, but cardboard none the less...
I'll add to the thread periodically, when I have time to make changes...
Dated tentatively by the speaker to 1955 (the photofact doc is dated 1957, but the schematic on the back looks older, too.)
Typical 6V6 PP output stage. Looks like grid-leak bias for the first stage. 12AY7 Preamp and PI --but not a lot of headroom. Has a very overdriven sound, think 50's Valco/Supro.
Has problems, of course. Fixed already: the OT was bumping up against the speaker (missing chassis screw)--that loosened the bolt which was also the GND for the can cap AND the shared 6V6 cathode bias resistor (check that out BTW--the loose resistor cover.) Those two issues sorted out--temp fix for the ground, and the bias resistor replaced with a nice 10 watter.
Now, it sounds good for 5 minutes. Then distortion begins--starts with a "creaking floor board" sound as the note decays, then gets progressively worse as the amp warms up.
NO--I haven't replaced the 12AY7's yet, just the 6V6's. I'll check downtown for new ones this week.
I'm not yet asking for input (although feel free to offer it), just wanted to document the amp, for which there are few photos on the interwebs... I thought yall might enjoy seeing this oddball old amp (and the great 60's contact paper...) Someone's missing their tablecloth, too. Also, under that nightmare the cab is cardboard, like some of those Dano amps. Half-inch thick cardboard, but cardboard none the less...
I'll add to the thread periodically, when I have time to make changes...
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