EKCO AD75 Restoration

[Dickie]

I've finally got the chance to get the AD75 kit I "won" from Glyn (Welsh Anorak) on the bench to have a look at it and make a shopping list of all the model specific parts that are missing. I new already it would need a new loudspeaker, baffle board, knobs, and a back. I will try and flatten out the tuning dial using the process described elsewhere on the forum. Luckily I found that all the main wound components were OK and showing sensible resistances.

In the process I found that this appears to be a bit of a hybrid between the pre and post-war models. It has a combined volume control/ mains switch (which appears to be original) which according to all the sources I've come across make it a 1939 model. Yet it has the post-war International Octal valve line up, which also appear original. All except for what ought to be a CBL31 but is actually a PEN453DD with a retro-fitted Mazda Octal valve base. This mod. was clearly done many years ago. The chassis has a s/n of 54197. How does this compare with other members sets?


The PEN453DD is a close, but not exact substitute for a CBL31. It presumably works OK and time will tell. This won't be a quick restoration, so watch this space.

[stevehertz]

I restored an AD75 a year or so ago and the thread I started may include a few tips. Best of luck, it's a nice set.

https://www.vintage-radio.net/forum/...d.php?t=184238

[Dickie]

Thanks Steve. I recall I sold you a knob for it at the time! Should've kept it!

One thing I am having difficulty with is the thickness of the baffle board. I guess its about 1/4" ply, but it would be nice to get it accurate.

[Phil G4SPZ]

I restored an AD75 at the Black Country Living Museum some years ago. The tuning scale was too far gone to save, and I printed a replica on glossy photo paper, which has lasted well.

I also made a new back, based on photos of an original, cutting the slots into hardboard using a DIY router and a rudimentary guidance system of timber battens, G-clamps and my Workmate. The 'chimney/heat deflector' was made from some thin aluminium and glass fibre PCB material following the dimensions taken from an original. The paint finish was two coats of a roughly 50:50 mix of black and brown emulsion paints. Apart from the back taking almost two whole weekends to complete, it turned out really well. I also restored the radio itself, but as I have implemented a policy of not leaving vintage radios running unattended at the Museum, the set is acts as an extension speaker for a background music player - hence the wording on the back. It is currently in storage but should be on display in the re-located Cast Iron House later this year.

If you need higher resolution scans of any of the attached pictures, or others I took during the process, just drop me a PM. I can't claim responsibility for the cleaned-up dial scan, which was kindly sent to me by another Forum member whose name I have forgotten. Good luck with your set!

Phil

[vinrads]

What a fantastic job you have made of the back , it puts mine to shame , mind you I don't have a router . Mick.

[Phil G4SPZ]

Ahem... nor do I, any longer. I managed to over-tighten one of the plastic plunging clamps and snapped it, but fortunately long after I had finished the back!

[Dickie]

Hi Phil,
That's very impressive. You have a pm. I've finally got an excuse to buy a router! I've managed to flatten the dial but there is some loss of the lettering.

[David G4EBT]

Originally Posted by Dickie

One thing I am having difficulty with is the thickness of the baffle board. I guess its about 1/4" ply, but it would be nice to get it accurate.

Originally it would have been 'millboard' with the slots stamped out. You can still get millboard from vintage car restorers, but whatever method you used to cut it, it's fluffy and doesn't machine well. Plywood is problematical to machine, with slots quite close together, and will tend to splinter. The best options in my experience and that of others is to use either 3mm MDF called 'Medite', or hardboard, which is plentiful at DIY stores, and which I think most tend to use.

This is Medite:

https://www.cutmyplastic.co.uk/wood-...MaAusfEALw_wcB

To create an authentic replica, cutting the slots really calls for a router with a 1/4" or 6mm bit and a rudimentary jig to guide the router. Yes, you could cut the slots with a hole drilled at each end of the slot and use a hand fretsaw or powered scroll-saw to cut the sides of the slots, (I know of one forum member who has done that to perfection), but it would be rather laborious.

You'll need some kind person to do a tracing of the back panel on paper. (I draw outlines on the back of a piece of wallpaper).

Good luck with it whatever method you decide to use to create your back panel.

I've just noticed Phil's stunning example - top job!

[Dickie]

Thanks for the hints and tips David. I have just received the scans from Phil and will be reviewing all the various processes involved. I can see its going to be loads of fun!

My original issue was the thickness of the loudspeaker baffle board. ( Apologies if not clear). Due to my own impatience I have recreated one using 5/16" ply which I had to hand and is currently waiting for the loudspeaker mounting hole PCD before finishing off with some matt black paint.

[Phil G4SPZ]

Hi David, and thank you for your kind comments! I try to work to "museum-grade" standards in all my restorations, although few have ended up so good as this one.

By the way, I have searched the Forum and found that I made my replica Ekco AD75 back panel in July 2013, and that the kind Forum member who supplied the photographs and template was Ian, "IJK2008". I'll make a point of thanking him again as I hope the information he provided can be used by anyone who needs it. The cleaned-up dial scan was created by Paul, "Paul LS" in around 2010; Paul is currently listed as a "retired dormant member" so I won't trouble him.

[Dickie]

Hi Phil,

Thanks for the scans, they are invaluable. I have just read the thread you referred to and note that you decided to add a heat shield to protect the back. Interestingly, the set which was the subject of the Utube video I looked at had severe heat damage to the back panel near the dropper.

[Phil G4SPZ]

Originally Posted by Dickie

...you decided to add a heat shield to protect the back...

Yes, it was a bit of a late addition and unfortunately I don't seem to have taken any photos of it, but basically it was a piece of single-sided glassfibre PCB material around 3" by 3" and mounted beneath the hot air exhaust port adjacent to the dropper and output valve.

I think I used 6BA bolts and nuts to fix it to the back, but I placed a couple of washers on each fixing between the PCB material and the back panel, and from memory I fitted the PCB with the copper plating facing the back panel. This created an additional air gap between the heat shield and the back itself, and as mentioned, on soak test it seems to work fine.

[David G4EBT]

Originally Posted by Dickie

Thanks for the hints and tips David. I have just received the scans from Phil and will be reviewing all the various processes involved. I can see its going to be loads of fun!

My original issue was the thickness of the loudspeaker baffle board. ( Apologies if not clear). Due to my own impatience I have recreated one using 5/16" ply which I had to hand and is currently waiting for the loudspeaker mounting hole PCD before finishing off with some matt black paint.

My misunderstanding!

'baffle board' was quite clear, and of course 5/16" ply would be fine for that.

[Dickie]

A few pictures showing progress over the summer. So many other things keep getting in the way!

The cabinet now has a loudspeaker plus baffle board, although the speaker is a 1950s model and might get replaced if I come across a 1940's equivalent. It took me a while to realise that the lower edge of the baffle board is intended to provide location for the chassis to prevent it moving around.

The back was made according to instructions provided by David. I spent probably a couple of weeks making a router jig using principles described in David's Article in the bulletin, although I simplified it somewhat as it didn't need to be "universal". I will of course regret that the next time I have to replace a back. Having done that it was a simple matter to rout out the slots in an hour or two. Pictures and scans from Phil helped me finish it off. I couldn't find the recommended shade of muddy brown, so ended up using Dulux Heritage "Tudor Brown" Velvet matt emulsion, available in 125ml tins. It looks OK to me.

I managed to flatten the original dial using a domestic iron with it sandwiched between sheets of white paper, but it lost some print in the process and had also shrunk rather a lot over the years. So I decided to take the easy way out and invest in a ready-made replacement. This arrived quickly but surprisingly didn't fit! After some correspondence the vendor refunded my £24 so nothing lost overall. I concluded the best way out was to fabricate my own. So by photographing the original and with some careful image manipulation I have arrived at what I consider to be acceptable. A glossy print seems to be rigid enough as it's sandwiched by the baffle board but it may need a bit of reinforcement. I shall post this in the relevant place for others as there's no harm in having a choice.

So my thoughts are now turning towards the chassis, So it's off to Biggleswade to look for some spares and to rummage through the boxes for those elusive knobs!

[Phil G4SPZ]

Superb job!

[David G4EBT]

Truly excellent Richard.

Well worth the effort of making a jig to cut slots which are uniform in length and accurately placed.

Your label (and that of Phil's), is another great example that disproves the statement that 'you can't print white on a domestic printer'. It's true that you can't get the printer to apply white ink, which it doesn't have. But what printers do have, is the ability to not apply ink of any colour where you want white text to appear. They also have the ability to print pale tints which approximate to silver or gold lettering, (or light grey, light cream, or whatever), with a contrasting dark background.

If you take as much care with the restoration, as no doubt you will, it's going to be a 'stunner'!

Every success with it.

[Lloyd 1985]

That little set is coming on a treat! I have seen the correct Ekco knobs in boxes at the NVCF/ RetroTech before, they are certainly easier to find than the black and chrome versions. I did start trying to mould my own once, I think it’s time I had another go! My original mould fell apart, but I did get some knobs from it!

Best of luck with the restoration!

Lloyd

[Dickie]

Thanks for the kind words. I have to decide whether to go for a light restoration on the chassis or a full strip and repaint. Given the large amount of non-original parts in this set, I'm not sure it matters from a historical point of view.

[Dickie]

I would be interested to hear what other restorers have done about the mains filter capacitors C25/26. These are connected from each side of the mains to a notional "earth" connector on the rear panel. With nothing connected this accessible connector will float up to half mains(!) so we can't just replace like for like. I am inclined to just cut them out.

It begs the question as to why the filter was thought to be necesary at all? The AD75 (I thought) was intended to be a low cost receiver and others of the same era do not have any filter.

[stevehertz]

Originally Posted by Dickie

Thanks for the kind words. I have to decide whether to go for a light restoration on the chassis or a full strip and repaint. Given the large amount of non-original parts in this set, I'm not sure it matters from a historical point of view.

Everyone has different thoughts on this but for me that chassis looks in good enough condition to benefit from a good clean and spot derust, I personally would not repaint it. My recent one year long restoration of an Ekco ACT96 had a chassis in much worse condition and I never contemplated a repaint. But that's more due to pragmatism and fear than a desire for a better restoration. Good luck whichever way you go. Take a look at how bad my chassis was: https://www.vintage-radio.net/forum/...d.php?t=191690