I'm made mindful of the classic line from "Apollo 13" where the 'guys on the ground' are instructed to come up with method of adapting one type of air-scrubber to work in liue of another "We've gotta make this, using nothing but that".
I was given the Muter by Marc, some moons ago, and although it came with a range of CRT bases, it had none to suit our vintage sets.
So the hunt (the scrounge) was on for the parts I needed to build an adapter to suit B12A and B8H CRTs.. First off was the B12, which was donated by Trevor "Murphy V310".
This would have been "it" asa far as I was concerned, and I would have mmodified one of the existing adapters to take the B12, but then I thought it would make more sense to make a purpose built adapter for the job.. This led to the search for a B9A plug to make the connection to the Muter, and sure enough, VRATs to the rescue, in the form of Dave "Framer Dave" who donated just the perfect plug, with plastic shield, and pre-wired, so that saved me a job.
Now that could have been as far as it would have gone, but having a couple of B8H CRTs, and since there could be more in future, it seemed logical to include one of these too, and sure enough, another VRAT rescue, courtesy of Rob "Glowing Anode".
So.. Now I had the "Make one of these"
challenges, and I also had the "out of nothing but that"
pile of parts.
The next part of the puzzle was map out the wiring of the Muter, using data for the only CRT that I had; A) the CRT data, and B) an original adapter to work from, in order to cross referrence the wiring from the Muter, to the "known" CRT, and onto the B12 and B8 bases.. Fortunately I am in possession of small number of Mullard "Data Books", and as luck would have it, they were just old enough to have the data I needed, or so I thought.
I was easily able to sort out most of the wiring, but fell foul of my old foible of failing to recognise that in colour CRT terminology, A1 and G2 are the same thing, just different referrences!
I had a PM from Marc, and a reply from Mike "Cathovisor" in my "Cross-referencing CRT base connections for CRT tester.."
thread, both giving me the same advice "A1 = G2", only that Mike went one step further in pointing out that "A2 = G3" in this equation.. See thread, viewtopic.php?f=15&t=7611
So now I had everything I needed to make a start.
First order of business was to remove all remnants of old wiring and miscelaneous components from the CRT bases, then drawing out a plan/map of the wiring, and at the same time, cross mapping these with existing wiring on Rob's B9 plug.. Once I'd got that sorted, I was able to wire up the B12.. I tested this 'first phase' on a known B12 CRT, and what a (pleasant) surprise, it works! At first, I thought there was an error in my work (the "Short G1-G2" indicator on the Muter was glowing, very dimly, but glowing) however, setting up the Muter, and taking the readings, went exactly as per the instruction manual, and were more or less plausible.. Next, I needed to find some suitable wiring to connect the B8, and guess what? I struck lucky with some multicore signal wiring from an ancient cooling module from a computer server, so I whipped off a length of that!
Cross referencing to the B8 was a straightforward job, complicated only by my breaking off a solder lug from the B8, so a little bit of surgery was needed to transplant a redundant connector from the B8, into the place of the broken one.
Once I'd got the wiring job done, another test to check that it was working, and Bob's your uncle!
All that remained was to tidy up the overall wiring and neatness of the job.
Here are a few pictures of the progress....
Now... Looking at this last photo, you can perhaps get an idea of my disorganised style of working, but belive it or not, all the data I needed is now contained within this picture, but I'll defy any to decode it and get it right.