by digi2t » Mon May 02, 2022 7:53 pm
Well, I finally got it traced out.
It's true bypass, which figures considering there's no tails option on this version. There are later units with tails, as well as tube drive only option switch, but I haven't had time to suss these options out yet. The tails version probably isn't TB though. Drive only option probably just bypasses the delay section completely, using both sides of the tube as a booster. Or, maybe uses the JFET booster in between? Possible I suppose.
The power transformer consists of two secondary outputs; one output at 140VAC, which rectified ups to about 165VDC. The other secondary outputs about 17VAC, which is then rectified to DC, and then feeds a 12v regulator, which in turn feeds some parts of the circuit, and a 5v regulator that feeds the IC's. There is a part number sticker on the transfo, but to date, my search efforts haven't identified the manufacturer or supplier. The closest I've come to it is a model by Antek, which supplies a 160/140v high output, and two 6.3v outputs, which in series will give you 12.6v. This might be OK to power the 12v regulator and all the other schniz downstream.
The audio is first routed through one side of the 12AX7, then through the mix pot, followed by a JFET booster before hitting the front end of the delay IC. Delay time is variable via pot, or with expression pedal via a vactrol for isolation. Signal returns from the delay IC to the other half of the 12AX7, then back to the mix pot, and out.
That's it, in a nutshell.
I've sent the schemo to Phil for conversion, so don't expect a schematic until we've validated it. Might be a while though. Phil is in the process of scratching a "bucket list" project off his list, as well as the backlog of other projects that I've sent him over the past couple of months.