The Craftmans Shop > New from Old
Racal RA17 re-born : A trip down Memory Lane
awemawson:
Years back I had a great interest in Communication Receivers - in fact I had quite a collection of what other followers of electronics would disparagingly call 'boat anchors'.
Before re-housing the workshop and moving here (11 years ago) I reluctantly disposed of most of them, but I could not bare to get rid of my Racal RA17. This receiver, made in 1957, is iconic. At the time it was probably the most stable communications receiver and was priced accordingly. Used in huge numbers by the armed services and many 'listening posts' it played a large part in our cold war defence 'snooping' on the Eastern Block.
Why was it so stable. Well it used the 'Wadley Loop' designed by Trevor Wadley (a South African) at the invitation of Racal, and uniquely used a single crystal generating many harmonics, to control two local oscillators whose drift would self cancel. (a VERY simplified description)
I don't remember when or even where I got mine, but I have found traces on the Internet of me asking questions back in 2002, so it was before then !
Now it's been packed up for those 11 years. The capacitors and resistors in these sets are well known not to age well, and I do recall dimly from before I packed it up that it would benefit from some TLC - leaky capacitors and resistors changing value all contribute to reducing sensitivity and selectivity.
I've decided that at last I must get this unit back into commission, but sadly I no longer have the RF test gear that I did, and this set has some very complex filter networks (100 khz, 37.5 & 40 Mhz) that need sweep generators to set to the accuracy demanded.
So, biting the bullet, I'm planning to 'out source' the work to one of the very few people able to do it. This will include replacing all electrolytic capacitors, all paper capacitors above 4.7 nF, replacing all carbon resistors, and re-aligning the filter units.
It's had a few 'modifications' where non original sockets have been substituted for more common ones, and those mods will probably be reversed if possible.
To whet your appetite have a few pictures taken today when I pulled it out of the eaves storage where it's been all these years:
hermetic:
I used to fiddle with communications recievers when I were a lad, that looks like a beauty! I lived at the village shop in Langtoft, East Yorks, and well remember our lovely paper delivery lady, ariving to sort the papers on the dining table, where I was tinkering with a bare chassis, I casually wander over and picked it up, having forgotten it was still on.....................How she laughed!! I must have looked like Michael Jackson dong the dance for "Thriller" It bloody hurt!
awemawson:
So the next thing to work out is how to transport this megalith (97 lbs not including the 'desk mount' case!) the entire length of the UK while retaining some confidence that it won't be smashed to smithereens :bugeye:
Meanwhile have a fragment of the circuit showing a few of the pesky filters that need aligning :
Pete.:
I shipped an unused vintage 1940's tilley floodlamp to Australia without it getting damaged. The buyer stated that he didn't care how much it cost him so long as it arrived un-damaged. We bought a double-thickness cardboard box and a whole roll of bubble wrap. Of course that thing only weighed about 8-10kg not 97, but the concept is the same. Sturdy box and loads of bubble wrap to insulate it then parcel-strap it to a mini-pallet so it'll always remain right side up.
awemawson:
A bit more progress: I've managed to lug the beast out of it's eaves storage, down the stairs, into a wheel barrow, across the farm yard and into the workshop. Poor thing looked so forlorn sitting in a wheel barrow :(
I've also 'discovered' a nice ready made pallet complete with pallet sleeve and lid. To reduce the weight from 97 lbs to 67 lbs I've removed it from the table top case. This also has the effect of increasing the amount of packing I can fit between it and the pallet case.
At Pete's suggestion I've ordered a huge roll of bubble wrap. It will be swathed in the stuff as an independent parcel, then strapped down to the floor of the case before final stuffing when the sleeve is installed.
A bonus when I removed it from the case, was to find two copies of the manual tucked down the side of the RA17 - I do vaguely remember hunting around and sourcing them all those years ago.
Attached to the internal racking of the case was a label dated 29/1/65 showing it had been inspected at the Admiralty Surface Weapons Establishment further confirming it's nautical history.
One of the issues with these sets was the moving coil meter that was fitted. Made by Ernest Turner, the very fine wire of the coil was originally varnished with a varnish that over a long period became corrosive and dissolved the coil - testing mine it seems to work, so that's one hurdle over come :thumbup:
Thumb twiddling time now until the Bubble Wrap arrives
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