Eddystone EC10

[G4XWDJim]

I'm repairing one of these for a friend at the moment. The thing would work well for a while and then crackle and burst into oscillation. Changing the electrolytics tamed it but the crackle was still there and traced to the RF amplifier transistor, one of our infamous old friends, an AF117. Resting the hot soldering iron on its can temporarily cured it and it's behaving well now but I think I should change the all the AF117s for future reliability. There's about six in there I think.

Cricklewood electronics have AF124s at £4 a go which seems an astronomical price for a transistor. Any ideas chaps where I might get some at a more reasonable price.

The question I'd really like to get an answer to is - how good are these sets at SSB reception. I've never tried one before. It resolves SSB and improves a little if I add a few pf across the BFO injection capacitor but still sounds very warbly with a voices underwater sound.

For those with experience of this set can I expect it to be any better. Do I need to do more work in the BFO area or is this as good as it gets. I don't want to spend ages trying to fix something that can't be fixed.

Any help appreciated, thanks.

Jim

[HamishBoxer]

Wouldnt have thought too good on SSB without a product detector,i have one that also needs an o/haul inc AFs.If you find any at a good price let us all know.

Regards David GM8JET

For SSB turn the RF gain down so the injected carrier from the BFO is big enough.

[Andrew2]

I had a Mk1 a while ago (I picked it up for old times' sake as I had always wanted one when I was a lad).
There's no product detector, so SSB reception is facilitated by the injection of a small amount of BFO into the IF strip. It works, but it's a bit of a balancing act between RF gain and distortion. The problem is that you need a fair bit of BFO signal to produce clean audio, but that signal will cause the AGC to reduce the gain.
Of course you don't get this problem with a seperate product detector.

[MichaelR]

Originally Posted by G4XWDJim

The question I'd really like to get an answer to is - how good are these sets at SSB reception. I've never tried one before. It resolves SSB and improves a little if I add a few pf across the BFO injection capacitor but still sounds very warbly with a voices underwater sound.

For those with experience of this set can I expect it to be any better. Do I need to do more work in the BFO area or is this as good as it gets. I don't want to spend ages trying to fix something that can't be fixed.

Any help appreciated, thanks.

Jim

I love Eddystone radio gear. The EC10 is not however an outstanding communications receiver. For the time it was released it was ok but for SSB the above posts have given you excellent advice. Do not expect much perfomance as there is no product detector and the audio stage is none too good Imho.

Nice looking set though.

Mike

[Skywave]

And then there is the 'standard problem' of a design that consists of 1 RF stage, single conversion, 455 KHz I.F. = image reception above 14 MHz (approx.) - and deteriorating as one approaches 30 MHz.

IMHO - As it stands, it is a better 'communications receiver' than some of the Japanese all-valve sets that preceded it - but not by much. Eddystone produced some much better sets than the EC10 - but guess what? These tended to cost a good deal more. In fairness, however, I will concede that the EC10 was produced at a time when set-makers like Eddystone were experiencing fierce competition from the Far East for a set that was aimed at its particular market.

Al.

[G4XWDJim]

Originally Posted by merlinmaxwell

For SSB turn the RF gain down so the injected carrier from the BFO is big enough.

Thanks everyone. Although no one actually said the EC10 is definitely poor with SSB I get that impression so will spend very little time in that area.

I always use low RF gain with such a set for the reasons Merlin pointed out above. Many simple sets will give good very SSB if handled in that way. I've used a broadcast set with another near it to use the local oscillator radiation as a BFO with much better recovered audio than this EC10 gives. What I was hoping was that someone might say that their EC10 was much better, or just the same perhaps to give me an idea of whether it's worth spending more time with it. I think the BFO in the EC10 was intended for CW only although SSB was about at the time of its production.
Even the much criticised 9R59 will do better than this EC10.

Jim

[JHGibson]

For an article on rebuilding the EC10 and replacing those germanium transistors with reliable silicon types, see www.qsl.net/vk3jeg/edd_ec10.html
John.

[dave walsh]

Just as an aside, I recall these as being a bit intriguing when first advertised in
WW ie Eddystone, small, transistorised and as implied here, not very high spec.
It was a surprise to see a set from this maker that wasn't at the top of the professional ranger. This didn't lower the price though, so they were out of reach, especially if you wanted something serious. Until recently though I'd often notice that they seemed to be highly prized [and priced] if they turned up at Rallies. Perhaps it was the nostalgia factor or just the Antiques Market rule ie smaller, easily transportable items can often achieve premium prices.
Dave W

[Skywave]

Originally Posted by G4XWDJim

Even the much criticised 9R59 will do better than this EC10.
Jim

Ouch!

Al.

[MichaelR]

[QUOTE=G4XWDJim;400885]

Originally Posted by merlinmaxwell

I've used a broadcast set with another near it to use the local oscillator radiation as a BFO with much better recovered audio than this EC10 gives.
Jim

Jim the audio stage is non too good any way if you tune into a good broadcast AM station I think it will not sound very good.

Mike

[David G4EBT]

I have a great affection for Eddystones, both their radios, and the company itself, which has a most interesting history, and contributed hugely to the war effort of WW2, so I admit to bering a tad biased. They were the radios of my youth - far beyond my modest means, when they were the stuff of dreams (until I discovered girls!). In later life, nostalgia triumphed over commonsense and Eddytones became a middle-aged indulgence!
My Eddystone phase lasted about 20 years, during which time I owned most of them.

I think some of the criticisms of the EC10 are a little harsh, though perhaps - as with the (valved) Trio 9R59DS - it's stylish 'communications receiver' appearance promised rather more than it was able to deliver. But that said, the circuitry followed standard practice in its day and it did have a compliment of ten transistors, a push-pull output stage and an RF stage.

As with all Eddystone receivers, it was well designed, attractive in appearance, and very well built, with great attention to detail. The chassis is easy to work on, and the coil assembly is a delight to behold, with its silver plated wire.

It was attractive enough to have on display and use as a normal broadcast receiver, the slide rule dial was clear and open, and the flywheel tuning mechanism had a nice feel to it. True, it had a BFO rather than a product detector, but then it came out in the mid 1960s, when SSB was still in its infancy with radio amateurs. I don't think it was ever claimed to be anything other than for shortwave listening rather than for example, the receiving half of an amateur station.

As with the EB35, ('B' meaning 'broadacst' as opposed to the 'C' in EC10 being 'communications'), there was a main PSU avaiable as an accessory, which fitted on the back in place of the battery box. Unfortunately, one of the problems often encountered on the EC10 and EB35 was that of corrosion due to dead batteries being left in the radio to do their dirty work, just as surely as woodworm do in 'woodies'.

The EC10 MK11 (from about 1970?) had the addition of an 'S' meter and fine tuning, and the headphone socket was moved to the back apron of the radio. I always felt that the S meter looked somehow out of place, but then it wasn't styled into the layout of the original set.

When they do come on the market, if in good undamaged, unmodded condition, they don't hang around long, and command a good price., as well they might.

As to the quailty of its audio, if in a good state of repair, with electrolytics and out of spec resistors etc replaced, there's absolutely no reason which it out not to sound as good as any radio of its era, which - in the audio stages, will have used similar circuitry.

And be they valve or transistor, if old radios don't sound too good, getting them back on song is the very essence of our hobby is it not?

David.

[Phil G4SPZ]

Hi Jim,

For the warbly underwater-sounding voices on SSB, I wonder if the BFO or local oscillator is being pulled by slight variations on the supply rail due to loading changes at AF by the output stage? Are all the decoupling capacitors at various points along the circuit in good order? You could try temporarily connecting a large value electrolytic across the main DC supply rail and see if anything improves.

73 de Phil

[MichaelR]

Originally Posted by David G4EBT

As to the quailty of its audio, if in a good state of repair, with electrolytics and out of spec resistors etc replaced, there's absolutely no reason which it out not to sound as good as any radio of its era, which - in the audio stages, will have used similar circuitry.

And be they valve or transistor, if old radios don't sound too good, getting them back on song is the very essence of our hobby is it not?

David.

Well that is a matter of opinion David , when I tested a unit I could easily drive the audio to a point wherbyit was poor ( it behaved like a class B amplifier) . Most Valve eddystone radio's have good Audio , this is a transitor set and their first.

My opinion was made genuinely to advise Jim not to expect too much from the performance point of view.

I am also a big Eddystone fan , I have worked on them for years and to be frank is my main collection and interest so what you may regard as harsh critique , in fact from me is honest critique.

Mike

[David G4EBT]

Not trying to start an argument Mike - the point I was trying to make - not very well perhaps, was to not compare the EC10 with say the large expensive Eddystone mulit-valved EA12, 940, 888A etc, which of course would outperform it, but with other transistor radios of its era.

As I stated, the EC10 audio stage used circuitry very similar to other transistor radios of that era. Many on the forum wax lyrical about radios such as the Bush TR82, Roberts R200 etc, with a push-pull output stage, and anyone who is content with the audio quality of such radios, should be more than happy with an EC10.

The front end of the EC10 has an RF stage, (with the voltage stabilised by a zener diode), which made the set more lively than the more basic radios of the era which lacked an RF stage - an era when many SWLs were content with such offerings as the very basic (and of course cheaper) 4 valve Codar CR70A, and the Trio 9R59DS, both of which were touted as 'communications receivers'.

The EC10 had separate RF and AF gain controls, so the RF gain could be turned down on strong signals to avoid overloading the IF and AF stages, and had a selective audio filter to help combat adjacent channel interference on CW. The limitations of the BFO when trying to resolve SSB has been referred to, but as I said earlier, the set pre-dates the adoption of SSB by amateurs, and Eddystone only referred to the function of the BFO being used to resolve CW.

I'd reiterate that IMHO, it's a testament to those who designed the EC10, that its stylish external appearance, (which doesn't look out of place today), perhaps promised a little more than it was able to deliver, at a price outside the range of many who would have liked to own one, (myself included at the time!).

The last remnant of my Eddystone collection is a circular speaker in hammered silver, rather than the more usual black crackle.

David.

[Andrew2]

IIRC, the SSB audio on mine was OK as long as the RF gain was wound back. I used mine mainly to listen to topband (1.9 MHz) ssb nets and I don't remember any warble - just a slow drift, which of course was common on sets of that era. Higher frequencies (say above 7 MHz) were harder to tune accurately and the drift was worse.
As mentioned above, poor voltage regulation could cause the warble. Isn't there a zener across the supply to the IF strip? I think I recall reading that this could go a bit funny.
It's quite a shock going back to a 40-year old set after having a modern synthesised one!

[RobinBirch]

This may have been mentioned earlier but I recall an article in, I think, the Short Wave Magazine (I may be mistaken), on "imporving the EC10. This involved better regulation, reducing microphony from the rigid wires going to the coils and some mechanical changes to make the front end more stable. There were a few other things but I can't remember them.

I beleive that I've got these tucked away somewhere, I'll try and look them out.

Regards

Robin

G5HI