loylo wrote:It looks a bit different from the circuit board pics on Keeley's website. Specially in between the 2 jacks, where there are shorts and Q1 unpopulated.
In fact that seems to be the only real change to the PCB, and it appears that as a compromise for removing the additional LED clippers the series resistor (R7) has been upped.
As for Q1, the board looks to be the same as is used in the 1962x version that adds in a MOSFET clipper for "KT88 mode", that's your Q1. On that subject, I'm guessing that in the "x" version D2 is still jumpered and it's pads are only present on the board for backwards compatibility. Also, from the one image that I've seen of the reverse of a 1962x, C1 was added but C10 was left unpopulated.
loylo wrote:According to Keeley's description, it is a Katana split in half (Q5 and Q6) and a Marshall Bluesbreaker in between.
This is indeed correct, and might serve as a useful starting point for determining the unknown capacitor values.
Anyway, here's my crack at a schematic:
1962x_sch.png
Though the values I have for the resistors seem reasonable, they're probably still worth checking.
However a thing that's left me scratching my head is the presence of R3, R4, C2 & C3 which appear to be in the (negative) feedback loop of the first opamp. Conventional thinking would dictate that they are responsible for forming a high pass filter, thus would be connected to ground as in the regular Bluesbreaker, however there is no ground pour on that area of the PCB and I can't see any traces going to ground (or otherwise). Although the traces in that section of the board are not clearly visible in any of the photos, they must still join up elsewhere where they should be visible and AFAIK I've not missed half a trace somewhere...
... so that begs the question am I going blind, mad, or otherwise?

As for the schematic, I've just assumed that it is as per the Bluesbreaker.
1962x_brd_.png
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