I see how very helpful they were. So, it looks like this is going to be another backwards engineer so that a correct transformer could be used.Copied and pasted marshall support emails. yeah help me find the info..Over the years I got about ten guys contacting me if I ever figured it out. They wanted to do it too. go bottom to top-
Must have been a marketing thing to build something like this in a 1U rack, because any tube engineer in their right mind would never use such a small chassis.
Ok, since we are 6bq5/el34 I would have to say its a transformer with specs around 400V b+ with 30V bias and 6.3V heaters. Now I would have to get you to measure the physical size of it (diameter and height). I would have to guess its probably one of the European odd sizes of core that were not efficient and most have discontinued those core sizes in their main offerings. But never the less, there are some that would be close enough in the current standard sizes. Like a 72VA or a 70VA core would be close in size to the outdated 67VA core for example.