Eddystone 850/2
 

A while back I asked about the Eddystone 850/2 receiver as I had one in my sights - Well it followed me home this weekend.

It looks to be a very clean (shelf dust mostly) early model Serial Number is DEV0003. I have joined the Eddystone groups.io list also. Seems like a wealth of knowledge between these two groups.

Couple pics attached.

Tom
W3TA

Re: Eddystone 850/2
 

great find and love that serial number.

Re: Eddystone 850/2
 

Very nice and super clean enjoy.

Re: Eddystone 850/2
 

Dev Protoypes were often used as patterns for the assembly line to build against.
Chris G0EYO

Re: Eddystone 850/2
 

Fascinating... I wonder what it would have been used for? [the frequency coverage is 'interesting'].

I note the presence of a red-and-black Plessey electrolytic, and what looks like a bunch of the TCC Metalmite/Metalpack capacitors which - despite their metal cases and moulded-rubber end-bungs are just waxies-in-posh-jackets and will be leaky as anything.

Re: Eddystone 850/2
 

Nice one- shame about what look like two broken toggle switches, though. Eddystones often have neat mechanical detailing, though the passive components can be distinctly unexceptional in quality. No great restoration traumas there by the looks of it. Should make a good NDB finder, plus it would be interesting to see how many of the remaining powerful European-area LW broadcasters make it across the pond!

Re: Eddystone 850/2
 

Thank you all for the informative replies.

Given that it seems to be a development radio, now I wonder whether I should replace the necessary parts to make it operational (don't know if it is or not, but usually a cap or two need to be replaced before powering these old radios up) or leave it as is? I don't want to upset any "originality" value it may have by replacing parts.

I would like to find some original style switches to replace the two broken ones though.

Tom
W3TA

Re: Eddystone 850/2
 

The photos show a very close resemblance to the Eddystone 888A - which covered the 6 LF / MF amateur radio bands then in existence during the 1960s / 1970s. And that radio was a really fine performer.

Al.

Re: Eddystone 850/2
 

Hi Tom,

Are these the type of switches you need. Often made by Bulgin I think. You're welcome to these two If they'll help.

I did quite a bit of work a dozen years ago on my 850/4. It was good for listening to the Alexanderson alternator on 17.2kHz and aircraft beacons on low medium wave. They've almost all gone now.

Realignment on the very VLF band was tricky. 3 point tracking I seem to remember. It was also useful as a signal tracer.

I've mislaid the memory stick which contains my photos so I'm not able to remember the serial No. I don't think it had dev on the plate.

Jim

Re: Eddystone 850/2
 

Sorry Tom, I didn't look at your pics properly and assumed the switches would be like the ones on mine. Even so the correct switches should be available over here.

Jim

Re: Eddystone 850/2
 

G4XWDJim said:
Now you'll get another go....

I do have an HP 3586A SLM which goes down lower than that with great sensitivity but unfortunately lots of local noise and only a small antenna!

Re: Eddystone 850/2
 

Hi Tom, hopefully you'll get a reply notification from this forum in connection with;

https://antiqueradios.com/forums/vie...p?f=5&t=402205

Yes, it was often the Eddystone way to use solder as glue for jointing, rather than making a prior secure (twisted-up) mechanical joint. It must have taken a bit of practice to make a neat joint where 3 or more wires needed to be connected together, but it does make repair easier in what are frequently closely-packed sets. Most British practice with point-to-point circuitry was to make a secure mechanical joint before soldering- particularly with professional/military kit, indeed I'm surprised that Eddystone didn't encounter a requirement to do things this way with some/much of their production. There have been previous discussions on this forum in connection with this aspect of Eddystone practice in particular, and some other manufacturers. In general, the joints seem to fare OK over the years, though in the 750 here (a compact dual-conversion general coverage set) two butted joints had fractured and failed where stud-mount caps had been angled toward coil-former tags and bridged with solder- not so good really.

Check the tube pin operating voltages- Eddystone, whilst good at neat and generally sturdy mechanical detailing, did not always use the best passive components and the chances are that there are quite a few off-value resistors and leaky capacitors after half-a-century or so.

Mods, I hope that this slightly oblique way of responding to Tom's query isn't too out of order, whilst I follow Antique Radio Forums, life's too short and otherwise busy to be a member of everything!

Colin

Re: Eddystone 850/2
 

Hello Colin,

Thanks for the response. I found it interesting, the way the soldering was done, but now that I've had to replace several parts, I find it easy to work with.

After spending enough time chasing the weak signal issues, I was finding bad caps in each circuit (one shorted and took out one of the 1K resistors - wife, "what smells down there.....").

Pretty much every bypass cap I've replaced has been way off. Found a couple resistors along the way too. I'm about 50% through the re-cap. I'm doing a circuit each night so I don't get too far ahead of myself. Should be done mid week and powering back up again.

Since the radio was pretty original, I was hesitant to start replacing parts, but I wanted a working radio not a shelf queen so out came the soldering iron.

I did find one area that didn't match the schematic and appeared to be factory installed. It involved the ACG circuit and V2, Schematic shows 470K to gnd from V2-2, but radio has 470k to 0.5uf bypass to 470k to the AGC bus. Looks at a different model Eddy and it is similar to that radios circuit. So I suppose that was a running mod that didn't make it to the schematic.

As much as I like originality, I like operational more and hopefully after this surgery it'll play the way it is supposed to.

Tom
W3TA

Re: Eddystone 850/2
 

Sounds as if they decided to include the ECH81 mixer in the AGC loop as well as the RF and IF stages- there was a feeling that it was unwise to subject the mixer to AGC in decent HF comms receivers to avoid oscillator pulling but for a receiver with a maximum oscillator frequency of only 1320kHz the effect is probably pretty much insignificant. Perhaps the AGC wasn't deemed to be sufficiently effective originally.

I agree that it's good to give something like this the opportunity to show how well it can perform with decent modern passives- the valves/tubes and wound components of the era were highly-developed and well-understood circuit elements that we won't see again but modern resistors and decoupling capacitors are much better than they were all those decades ago. Some vintage components- stud-mount Dubiliers, Aerovox bath-tubs, big old body-tip-spot "dog-bone" resistors do admittedly look the part but those awful red-and-black Plessey electrolytics with the yellow waist-coat just make me wince and look away.... Same with the various low-cost paper capacitors that were encapsulated in brittle red/brown/black plastic, the smaller ones often referred to as "rat-droppings" and about as useful by now.

Re: Eddystone 850/2
 

When I first saw them I thought they were resistors. Then studied the schematic and saw they were caps. Measured capacitance is way out of spec so those were replaced also. Like their nick name...... rat droppings.... good one!

Tom
W3TA

Re: Eddystone 850/2
 

Finally got the radio working - pretty well actually. I ended up diving in head first and replacing every capacitor that was not the mica type. Found several out of whack resistors along the way.

Powered it up - nothing, no sound - great.... Reviewing all of my handy work found one resistor installed one pin off - put it on the correct pin and things start working. Funny how that happens.........

IF and RF alignment went well, had some difficulty on band 6 but I believe I have it sorted not - nothing to hear down there anyway.

Couple pics of the finished (not in cabinet) product. Time to put the covers on, find a place in the shack and move on to the next radio. I think I'll tackle the SX-28A that has been patiently waiting its turn on the bench.

Thanks for all of the suggestions, discussion and help.

Tom
W3TA

Re: Eddystone 850/2
 

Nice work there Tom, that'll have it working well for a good few years yet. There are still a few powerful European/North African LW transmitters on the air, including the UK's BBC Radio 4 on 198kHz and the Irish Republic's national service on 252kHz, maybe some of them can be heard in the US with the right aerial and circumstances. It could even double as an item of test gear for other sets' mixers/IF strips,

Colin