04-09-2013, 05:36 PM
I've mentioned a few times in various posts that some 30 years ago I bought an Ekco AC77 intending to restore it, but when I took the back off, I could see that it was so decrepit that it would be a total strip-down to the last nut and bolt. I've looked at it several times since, and have been ambivalent as to whether it was worth the effort involved. However, I've become a bit fed up with the usual run of the mill restorations - change a few caps resistors and valves etc, so I decided that even though this isn't as sought after as the round Ekcos (the only one of which to my mind is well designed being the A22), I'll take the plunge. I'm not interested in the ultimate value of the set, (or any set for that matter), which has never been a consideration for me - I'm interested in the challenge and range of skills which such a set presents.
Here's the story so far.
I should say at the outset, that my approach to restoration is that safety overrides all other considerations such as originality. The older a set, the more I try to conserve what's there, but only insofar as that doesn't compromise safety, reliability or functionality.
The first consideration with this set is that the dial has almost no markings on it, and efforts to obtain a scan or even a pic of a dial have drawn a blank, and without a dial, it would be a non-starter. However, someone (Robert Darwent or Gary?) kindly tipped me off that Ben Djikman in the Netherlands does a dial for the AC77. However, the spelling on the dial is 'European' rather than English (EG Frankfort not Frankfurt, Britisch - not British), but Ben said if I could get 20 or more people interested in placing orders, he'd get the screen print artwork amended for a British version. There's no prospect of that happening, so I bought the European dial, and must say it's excellent, especially that it was either that, or no dial at all.
Initial investigations suggested that the mains transformer and field coil were open circuit. However, the set was in such a state that I couldn't be sure until I removed the field coil and power supply to check further. The power supply is on a separate chassis from the main chassis, which makes life a bit simpler, and is very similar to the AC97 (often nicknamed the 'Cyclops' or 'Robot'). Luckily, Gary Tempest did a complete restoration on an AC97 which featured in an 8-page well illustrated article in the Autumn 2008 Bulletin and on the front and back cover, which has been a big help.
Luckily, my fears about the mains transformer proved groundless. The fault lay with the voltage selector panel, for which I made a new brass spring strip and a new voltage selector screw. However, as suspected, the field coil was open circuit so would need re-winding. True, there are a number of people who would do that for me, but that would make me a 'fitter of parts' rather than an aspiring restorer worthy of the name. The thought crossed my mind "in this situation, what would Gary, Robert, Colin Wood, Tony Thompson or other such restorers (rather than 'do-uppers') who set the bar so high do?" I think I know the answer - they'd rewind the coil by one means or another, and Gary again wrote an article some time back in the Bulletin for a coil wider he designed ('Making a Coli Winder - Mostly from the junk box'). That gave me another challenge - make a coil winder that will put upwards of 2KM of 38 SWG wire on a bobbin.
So, in this thread I'll stick to the AC77, and in another thread, I'll report on progress to date on making a coil winder powered by a sewing machine motor. (far too many turns to do it by hand).
The AC77, as with the AC97, has two flimsy tag strips on the rear apron of the power supply chassis which mate with two partner tagstrips, held together with solder. There's no way that I'd consider using the same tagstrips, so an alternative arrangement was called for, along similar lines to that used by Gary on the AC97. I had some 'turret strips' which though they spacings didn't exactly match up, were near enough to fit the aperture in the rear apron. I fitted the new strip inboard of the chassis.
I removed the power supply chassis and all of the components on it, de-rusted the chassis and re-sprayed it Ford Dove Grey, which Gary recommended as a good match for the original Ekco grey. I cut open the electrolytic can near its base, cleaned it out skimmed the two parts on the lathe to make a good fit, and made an aluminium sleeve to join the two parts together. I stuffed it with a BVWS replacement. The can was very pitted, so I spun it up on the lathe and polished it with U-Pol pad and Duraglit. That of course obliterated the original wording, so I made a waterslide transfer to add some wording as to what was inside the can.
On the underside of the chassis, there was a 'service replacement' Hunts (arrgh!) capacitor block consisting of two 8uF caps in a printed cardboard box. It had been bodge in and was swinging loose on its wiring. It's my guess that it was bodged in during the war years. Out of curiosity I tested it on an analyser, and it came up not as a twin cap, but as a pair of 10Meg resistors! I made a replacement block from double sided PCB sheet soldered together, covered the box with glued on brown wrapping paper, and made a label for the box. I tried to 'age' it by coating it in beeswax but that was a step too far and looks out of keeping with the rest of the work, so I'll re-do that and simply coat the new label with shellac sanding sealer.
I've de-rusted and re-sprayed the mains transformer and made an fitted a new brass spring strip on the voltage selector panel, and a new voltage selector screw, the tip of which I turned down on the lathe. The original screw was barely long enough and was badly corroded. I found a little knob which as luck would have it, had a threaded 4BA brass insert so was a good replacement for the original. Ideally, I would have liked to have fitted a new 3mm paxolin strip to replace the bowed 2mm original strip but that would have meant unsoldering flimsy wires on the transformer primary, so I left well alone.
I replaced a small wire-wound open circuit resistor lurking behind the tagstrip and rewired the chassis using silicone rubber wire (from Phil Marrison, who usually has a table at the NVCF), which I use for all my restorations. It comes in a wide range of 'vintage' colours and strips nicely. It would have been nice to have retained or replaced the cotton covered original wire to look truly vintage, but I had the silicone rubber flex to hand and it looks much nicer than PVC as well as being heatproof.
(The field coil restoration is a project in its own right, which I'll mention in a thread on the field coil winder which is in progress).
That's the story so far!
I've attached some pics of progress to date.
Hope it's of interest.
(This restoration is destined to have a longer run than 'Mousetrap'!)
Here's the story so far.
I should say at the outset, that my approach to restoration is that safety overrides all other considerations such as originality. The older a set, the more I try to conserve what's there, but only insofar as that doesn't compromise safety, reliability or functionality.
The first consideration with this set is that the dial has almost no markings on it, and efforts to obtain a scan or even a pic of a dial have drawn a blank, and without a dial, it would be a non-starter. However, someone (Robert Darwent or Gary?) kindly tipped me off that Ben Djikman in the Netherlands does a dial for the AC77. However, the spelling on the dial is 'European' rather than English (EG Frankfort not Frankfurt, Britisch - not British), but Ben said if I could get 20 or more people interested in placing orders, he'd get the screen print artwork amended for a British version. There's no prospect of that happening, so I bought the European dial, and must say it's excellent, especially that it was either that, or no dial at all.
Initial investigations suggested that the mains transformer and field coil were open circuit. However, the set was in such a state that I couldn't be sure until I removed the field coil and power supply to check further. The power supply is on a separate chassis from the main chassis, which makes life a bit simpler, and is very similar to the AC97 (often nicknamed the 'Cyclops' or 'Robot'). Luckily, Gary Tempest did a complete restoration on an AC97 which featured in an 8-page well illustrated article in the Autumn 2008 Bulletin and on the front and back cover, which has been a big help.
Luckily, my fears about the mains transformer proved groundless. The fault lay with the voltage selector panel, for which I made a new brass spring strip and a new voltage selector screw. However, as suspected, the field coil was open circuit so would need re-winding. True, there are a number of people who would do that for me, but that would make me a 'fitter of parts' rather than an aspiring restorer worthy of the name. The thought crossed my mind "in this situation, what would Gary, Robert, Colin Wood, Tony Thompson or other such restorers (rather than 'do-uppers') who set the bar so high do?" I think I know the answer - they'd rewind the coil by one means or another, and Gary again wrote an article some time back in the Bulletin for a coil wider he designed ('Making a Coli Winder - Mostly from the junk box'). That gave me another challenge - make a coil winder that will put upwards of 2KM of 38 SWG wire on a bobbin.
So, in this thread I'll stick to the AC77, and in another thread, I'll report on progress to date on making a coil winder powered by a sewing machine motor. (far too many turns to do it by hand).
The AC77, as with the AC97, has two flimsy tag strips on the rear apron of the power supply chassis which mate with two partner tagstrips, held together with solder. There's no way that I'd consider using the same tagstrips, so an alternative arrangement was called for, along similar lines to that used by Gary on the AC97. I had some 'turret strips' which though they spacings didn't exactly match up, were near enough to fit the aperture in the rear apron. I fitted the new strip inboard of the chassis.
I removed the power supply chassis and all of the components on it, de-rusted the chassis and re-sprayed it Ford Dove Grey, which Gary recommended as a good match for the original Ekco grey. I cut open the electrolytic can near its base, cleaned it out skimmed the two parts on the lathe to make a good fit, and made an aluminium sleeve to join the two parts together. I stuffed it with a BVWS replacement. The can was very pitted, so I spun it up on the lathe and polished it with U-Pol pad and Duraglit. That of course obliterated the original wording, so I made a waterslide transfer to add some wording as to what was inside the can.
On the underside of the chassis, there was a 'service replacement' Hunts (arrgh!) capacitor block consisting of two 8uF caps in a printed cardboard box. It had been bodge in and was swinging loose on its wiring. It's my guess that it was bodged in during the war years. Out of curiosity I tested it on an analyser, and it came up not as a twin cap, but as a pair of 10Meg resistors! I made a replacement block from double sided PCB sheet soldered together, covered the box with glued on brown wrapping paper, and made a label for the box. I tried to 'age' it by coating it in beeswax but that was a step too far and looks out of keeping with the rest of the work, so I'll re-do that and simply coat the new label with shellac sanding sealer.
I've de-rusted and re-sprayed the mains transformer and made an fitted a new brass spring strip on the voltage selector panel, and a new voltage selector screw, the tip of which I turned down on the lathe. The original screw was barely long enough and was badly corroded. I found a little knob which as luck would have it, had a threaded 4BA brass insert so was a good replacement for the original. Ideally, I would have liked to have fitted a new 3mm paxolin strip to replace the bowed 2mm original strip but that would have meant unsoldering flimsy wires on the transformer primary, so I left well alone.
I replaced a small wire-wound open circuit resistor lurking behind the tagstrip and rewired the chassis using silicone rubber wire (from Phil Marrison, who usually has a table at the NVCF), which I use for all my restorations. It comes in a wide range of 'vintage' colours and strips nicely. It would have been nice to have retained or replaced the cotton covered original wire to look truly vintage, but I had the silicone rubber flex to hand and it looks much nicer than PVC as well as being heatproof.
(The field coil restoration is a project in its own right, which I'll mention in a thread on the field coil winder which is in progress).
That's the story so far!
I've attached some pics of progress to date.
Hope it's of interest.
(This restoration is destined to have a longer run than 'Mousetrap'!)
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
