I've been rummaging again and found a few old Polaroids (remember them?) of the 400-Watt mediumwave transmitter. You can read the full terrifying details in the Pirate Chat articles on Aquarius One, but briefly it went like this: A transistor crystal oscillator (running at twice frequency and divided by two) drove a valve - an ECC83 if I remember correctly - which in turn drove a 5763 which, in the early version pictured here drove a single 813 which had about 2.5Kv on top. I later added a 6146 and an extra 813 for more smoke. The original plan was to anode modulate the PA with a pair of 811A's via a specially-wound modulation transformer, but we couldn't get good audio this way. In the end we kept the modulator as it was and modulated the screens of the 813's. Plenty of mod and excellent quality too.
These old photos had gone very brown over the years and were also developing sparkly bits. A session on Photoshop got them looking remarkably good.

As the smoke clears... sorry about the mess. In theory this was my Mum's back room, but I claimed it as the Aquarius Reasearch Lab. Here's the TX in it's early 'lash-up' test. You can see the whopping HT transformer at rhe right front and the string of electrolytics. Ive counted at least six transformers, but I'm blowed if I can remeber what they were all for. The two large valves sticking out of the vertical chassis are the 811A's.

Another angle. Now we can see the single 813 resting on the floor. It had a habit of scorching the floorboards if I recall correctly. No mod transformer yet - it was on order from Magtor, who quoted us the princely sum of £18. Eighteen pounds? Do you think I'm made of money? That was about a weeks wage back then! I don't think we ever paid.

My fellow Aquarian Bob has put some more photos here:
http://picasaweb.google.com/radprog/RadioAquariusManchester