Just a crazy thought, that silicone moulding stuff that I bought to make moulds of the knobs; could that be used to make a mould of the entire front of the cabinet of a good one, then the remnants of yours could be placed into the mould and resin poured in to complete it? That would capture the detail from the original, and you could still use the plywood for the sides. Wouldn’t be cheap to make the mould though!
Hi Lloyd, I'm receptive to any new ideas to effect a repair to the cabinet. Like your A22 chassis was before restoration, this one is also in an awful state, but it works surprisingly well. In fact, it's a better performer than other A22 I serviced last year.
I bet you all thought I'd given up on this set! Well, fear not! I'm back at it again, after a long break.
Like many people around the country I got 'furloughed' (sounds really unpleasant...) for a month, June to be exact, and I also had booked the last week of May off, so had a whole 5 weeks all to myself! This gave me the time I needed to complete a few outstanding things that I'd left for far too long, one of them being a workshop tidy up, sadly it took nearly the full 5 weeks, but it was worth it, I now have room to move, and I've moved stuff into new locations which make much more sense than before. I moved the bench just a short distance closer to the door, moved the Murphy V250C with the Ekco T368 on top to the far end of the workshop, fitted some extra sockets around the bench and some on the end of it, with their own 'bench switch' and also permanently fitted the isolating transformer to the bench too. The lathe has moved into the cupboard under the bench, making it easier to get to as well. There's still not enough room! I could have done with building the shed just about 2ft wider.
So where is all this leading? To the A22 project of course! With the lathe now accessible, and the drill press too, I had no excuse not to get on with making up the aluminium inserts for the knobs, so I have done just that, 3 inserts were turned up out of the same piece of 1/2" ali bar that I used for the dial spacer, around 16mm in depth, and scored the surface to aid adhesion of the resin. Whist drilling out the bar, the drive belt on the lathe decided that it had had enough, and began self-destructing, but it held on long enough to finish the inserts.
with that bit done I set about wondering how I was going to hold the inserts in position whilst the resin sets, I attempted making a jig that would sit over the top of the mould, but gave up. The best I could come up with was using the pilau drill, with something in the chuck to attach the insert onto, and then find a way of keeping the drill set in position. I used a wooden dowel turned down a little so the insert would be a snug fit onto it, and to keep it set to the right height I spotted a grub screw in the side of the drill, which when tightened stopped it moving up and down. Perfect! Sadly, I could only make 1 knob at a time like this, but it's better than nowt!
I put one of the original knobs back into the mould to line up the dowel in the centre, and carefully removed it without moving the mould, then mixed up the potting compound and put the insert on the dowel, after first sticking a bit of Kapton tape over the end so the resin wouldn't go into the insert and stick it to the dowel. I smeared the resin onto the insert first, and then poured a small amount into the mould and spread it over the inner surface of the mould, in the hope that it'd reduce the chances of voids in the final piece. The insert was then lowered into the mould and set to the right height by eye, and the grub screw on the side of the pillar drill was then tightened to stop it moving, then the leftover space in the mould was filled with resin, quite a messy process with the smaller knobs as the chuck was in the way a bit! I mixed up far too much resin, so I dug out some other moulds and used up the remainder in those, with varying degrees of success, the biggest one was a mould for a knob off the side of an Ekco U76, which turned out rubbish because the mould had shrunk and deformed a bit.
So I now have a full set of knobs for the A22! Just a tiny bit of fettling to do, the backs need sanding flat, and the hole needs drilling and tapping for the grub screw, hopefully I won't stuff it up! So long as I can clamp the knobs nice and safely in the vice, and drill slowly, I should be OK. I've still got to wait for the resin to fully cure, which takes around 7 days, I may have not mixed in enough hardener with the first 2 knobs, as they are still a bit soft, whereas the last one I did is rock hard already, hopefully the other 2 don't stay soft!
I'm planning on getting some brass bar, and some new 1/4" drills to have a go at making a few more, maybe try different resin and come up with different colours, the brown/ walnut type will be most difficult, trying to get the swirls of black and brown correct. I do fancy having a go at making the spare chassis into a red cabinet version! Making the mould for the cabinet would certainly be interesting, I'll keep trying to perfect the smaller items before moving on to anything that big though.
Absolutely top notch work there Lloyd, informative write up too, this is such an excellent basket case restoration thread ? Folk really need to go back and look at the initial photos of the radio to remind themselves of what you took on.
Those knobs really look authentic, you've certainly got the moulding process under control now. Can't wait to see them on the set.
p.s.
Now shared on the Vrat Facebook group, gotta feed the radio guys N gals over there, I can think of no better example than this 'insane' A22.
Cheers Chris! I know, I sometimes look back at those photo's and it even surprises me just how bad it was.
I did actually peel off the excess on those knobs and put them on the radio and took a photo, but decided not to post it as it was too dark, and you couldn't really see them, I'll have to take it out into the daylight and try again!
I'm not 100% happy with them, somehow the aluminium inserts I put in have ended up off-centre by quite a bit, which although isn't obvious straight away, it's very noticeable when turning the knobs. The wavechange switch isn't really noticeable, since it doesn't do a full rotation, so I can get away with that one, and the volume one is OK if I stick a shim on the pot shaft, but the tuning one is awful! I'm going to have to go back to the drawing board for that one, because I can't live with it! I did consider sticking the knob in the lathe and drilling out the insert and sticking in a new one, but after digging the lathe out again I've discovered that the tuning knob doesn't fit in the chuck anyway...
Other than that they are pretty good! A couple of pin holes in the 2 smaller ones, which I could fill with some sort of hard wax if I can find some. Now to buy some 1/2" brass bar that isn't overpriced, or taking 6 months to arrive from China..
I'm not 100% happy with them, somehow the aluminium inserts I put in have ended up off-centre by quite a bit, which although isn't obvious straight away, it's very noticeable when turning the knobs. The wavechange switch isn't really noticeable, since it doesn't do a full rotation, so I can get away with that one, and the volume one is OK if I stick a shim on the pot shaft, but the tuning one is awful! I'm going to have to go back to the drawing board for that one, because I can't live with it! I did consider sticking the knob in the lathe and drilling out the insert and sticking in a new one, but after digging the lathe out again I've discovered that the tuning knob doesn't fit in the chuck anyway...
Other than that they are pretty good! A couple of pin holes in the 2 smaller ones, which I could fill with some sort of hard wax if I can find some. Now to buy some 1/2" brass bar that isn't overpriced, or taking 6 months to arrive from China..
Regards,
Lloyd
Could you have cast the knobs the other way up, and place a small rod of the appropriate diameter in the centre of the existing hole, this leaving a centre in the new cast knob?
Did I miss the reason you're not changing the grille cloth??
No particular reason, I just haven't found anything suitable yet! To be honest, I haven't really looked very hard, I have some stuff I picked up from Sid Chaplin at the NVCF a few years back, which looks quite good on Ekco sets, but I'm not sure it suits this one, it's quite a coarse weave, and has plastic strands in it, where the cloth on the A22 is quite a fine weave. I did try a piece of dark wash denim, which I thought looked pretty good! Totally un-original, but I might go with it if I can't find anything else I like! But I will be changing that ratty old bit of cloth eventually, I just left it there to fill the hole for the time being.
Could you have cast the knobs the other way up, and place a small rod of the appropriate diameter in the centre of the existing hole, this leaving a centre in the new cast knob?
I may give that another try, the reason I cast the new knobs face down is purely because of bubbles, as I haven't any access to a vacuum chamber. On other types of knob that are all Bakelite, but hollow, I have managed to make moulds that take the shape of the rear of the knob, and capture the centre hole in the process, so I could do that with these knobs too. I think what I need to do next time is to really check that everything is square and level before putting the potting compound in. I'm going to make up some templates and maybe a jig or 2, I might even start from scratch!
Another thing I thought I could do is to make my own jaws for the lathe chuck so I can get one of the larger knobs to fit in it!
Could you have cast the knobs the other way up, and place a small rod of the appropriate diameter in the centre of the existing hole, this leaving a centre in the new cast knob?
I may give that another try, the reason I cast the new knobs face down is purely because of bubbles, as I haven't any access to a vacuum chamber. On other types of knob that are all Bakelite, but hollow, I have managed to make moulds that take the shape of the rear of the knob, and capture the centre hole in the process, so I could do that with these knobs too. I think what I need to do next time is to really check that everything is square and level before putting the potting compound in. I'm going to make up some templates and maybe a jig or 2, I might even start from scratch!
Another thing I thought I could do is to make my own jaws for the lathe chuck so I can get one of the larger knobs to fit in it!
I'm new to the forum but have been reading this one with interest. I've recently aquired an A22 which is in a fairly poor state. In particular its missing its feet (see photos). Would like to get it looking 'whole again in the shortish term and may attempt a full restoration following much of this thread at a later date. My main question is did anyone make any progress in moulding part of all of the cabinet. I would really like to mould the missing part of the cabinet to restore this one to its former fab shape. Thanks
I haven't got round to moulding part of the cabinet for mine yet, it's on my list of winter jobs, along with trying to mould the knobs for the second time. I remember seeing that particular set when it was for sale! I apologise, I may have pushed the price up a little bit.. I had considered using it for spares for mine! Pleased to see it's found a good home though 🙂
The stuff I use for making the moulds is 'Polycraft GP-3481-F RTV Silicone Mould Making Rubber' using the red catalyst, Easy to find on eBay, it's not cheap, but it's what works well for me, there are probably other types of silicone suitable for making moulds, I've just not looked into it! You might need quite a bit to make a good solid mould of such a large part of the cabinet, and you'll also need another good cabinet to make a mould of in the first place.
It's certainly going to be an interesting project, the feet need to be strong enough to take the weight of the set, and also any abuse such as being plonked down a bit too hard, they are one of the weak points of this particular design, as the original bakelite feet are hollow, and the bakelite isn't particularly thick either. One idea would be to make the new feet as one solid lump, but you may have problems with shrinkage, unless it was maybe done in layers with fibreglass matting in each layer. Another option is to make the feet out of wood!
Thanks Lloyd. Thanks for the pictures- it certainly seems to lack a certain something without the feet. No probs about the auction, that's how they work I guess! I'm pleased it's going to get a chance to survive intact though- eventually. My idea was to mould the feet with the original thin section, but then add layers of fiberglass on the inside to stregthen it and to attach the feet to the body.
Unfortunately to do this properly I would need an complete cabinet to make the mould. Maybe I could go halves with you on the materials on the basis I can use the mould to make the feet? I'd prefer to use mould the feet rather than make them out of wood if possible.
Time for an update on this almost forgotten project! It’s been sat in the workshop doing very little, occasionally being switched on just to have a tune about. This week I set about building a couple of pantry transmitters, they are the MiniMod design by Ian Liston-smith, that is available on The UKVRRR forum, with very nice PCB’s supplied by another forum member ‘Electronpusher0’, he had them made by JLPCB. I built 2 of them, and both worked first time! They are very good, nice clear audio, and they don’t radiate too far, so won’t annoy the neighbours, or Ofcom!
I tried one on the A22, but was having trouble picking up the signal on it, then I connected the aerial input straight to the MiniMod, and all the power went off! I was powering the MiniMod from the bench power supply, and also had the scope connected to it, the A22 was connected to the mains directly, no isolating TX.. you know where this is leading! The poor old A22 has an earth leak 🙁 it seems there is leakage between the primary and chassis, and is measurable with a DMM, around 5M, and with the Megger on its 500V range it drags it nearly to zero, then climbs up slowly, like it’s charging a cap, and when you release the test button it actually registers a voltage stored! Time to dig the chassis out and see what’s going on..
Other than that the radio is still working well! If the transformer has had it then I’ll probably look into using the one from the spares chassis, but then I’ll have to use a different rectifier valve as it doesn’t have the extra winding for the rectifier heater.
The MiniMods are really good and with vintage radios generally not having very narrow IF bandwidth can make the old radios sound good. Much better than the compressed MW signals that are off air.
I use mine with 6 AA batteries they last a long time.
Yes, they are excellent, I was really impressed with them, quite a simple little circuit, and easy to set up. I haven’t built them into a case of any description yet, as I’m wondering how to power it, whether it’ll be a PP3, 6 x AA’s or I might try something rechargeable, possibly some li-ion cells. I’ve been running the Ekco AC86 mostly over the last 3 days and it does sound good!
I was struggling to remember, but after a search through some more photo's I think they came from the 5 trimmers that sit under the left side of the chassis. I'll double check later, but I don't think they came from anywhere else!
I'm restoring my 3rd A22. In my pot 'pot of parts' I found three red fibre washers. They don't look to have been marked by being pressed to anything, so maybe they didn't even come from the set! But I can't think where else they came from. The trimmers on the one I'm working on have ceramic washers, although one had brown fibre ones like yours.
Maybe someone used them to help secure the back cover...
You may have noticed the discrepancy in value of the audio coupling capacitor. Documentation says 0.05uF, but all those I worked on were 0.005uF. No difference in audio whichever is used, though with the higher value the A22 does not react well to very strong signals. There are also some other component changes. If your set's got 220pF in the second IF transformer there's a 50pF cap on the curved board that's changed to 15pF.
