The last work I did on the set was to attend to the Band pass Filter Unit, which contains the wave-change switch.
Rather worryingly, the maker's service data states:
"The wave-change switch is incorporated in the same screening can as the bandpass input filter and normally should not be subject to atmospheric action.
Should the switch or bandpass filter give trouble, no attempt at repair should be made - the complete unit must be returned to EKCO works for replacement'.
Well it did give trouble - some connections on the switch were open circuit, and the shaft was hard to move. I fitted some heat shrink tube around the switch shaft to form a reservoir for Plus Gas penetrating fluid (never WD40 - ok for garden gate hinges, but not wave-change switches). (See pic I below). That enabled the switch to move freely, but on removing the cover from the filter, the wave-change switch appeared to be 'sealed'. On further examination, it was surrounded by a paper strip and coated in wax, (just visible in pic 2). On removing the paper there seemed to be as much congealed wax on the switch contacts as on the paper which had surrounded it.
I degreased the contacts and lubricated them with Servisol then fitted the cover back on. I made no attempt to disturb the fragile wires of the coils in the filter - wound on beech dowels and rather beyond my comprehension as to which coil is which as there is no diagram. (See pic 3). On testing the continuity and resistance of the coils and comparing them with the table, they seemed close enough to be acceptable, though the connections between 2 & 8 are a little high at 41R when the spec is 30R, albeit before cleaning the switch, between those point was open circuit.
Only time will tell if this unit is functioning correctly.
That's about the stage that I'm up to, so the next phase is to start wiring up the receiver chassis. The correct approach is of course to be single-minded and only deal with one project at a time, seeing it through to conclusion before starting another project. I've never really been able to do that as other projects pop up to catch my attention and off I go on a frolic. Last autumn I restored a little 'Figaro Special' which could have waited, then another one came along so I restored that for my younger son who shares my interest to an extent.
This week's sidetrack is a lathe rev counter I've just taken delivery of to fit to my woodturning lathe, which uses a magnetic proximity detector ('Hall Effect'). This is yet another act of frivolity on my part, as I can tell what speed my lathe is running at and I've got a non-contact rev counter which I just have to point at the lathe shaft anyway. But at only £12.00, I succumbed. Probably undiagnosed ADHD or something.
Really, having done so much at this AC77, which - as well as the Coil Winder project - has involved other ancillary projects such as making valve-base adaptors to enable me to test the AC77 valves on my Taylor 45 Valve tester, I should now get on with finishing the AC77, so that before the year is out, it qualifies as a 'success story' - not simply as 'work in progress!'