I need another radio like I need a hole in the head, but whilst on holiday this week in the Southwold area of Suffolk, I couldn't help but being drawn to this set in an antique-cum bric-a-brac shop. It was priced at £30, but I got it for 25 after a bit of sweet talking to the charming old lady at the counter. No pic's as of yet, but will pick up when I get back home. This set is in quite good condition and should restore nicely. It is a rather nice FM only receiver with twin loudspeakers.
To understand the black art of electronics is to understand witchcraft. Andrew.
It’s a standard valve line up, ECC85 front end, 2x EF89 IF amp, EABC80 detector and AF amp, EL84 Audio output and EZ80 rectifier and EM80 magic eye. 87.5-100 MHz, standard for this age of set, two loud speakers, should work well.
Must look out the circuit in the next few days.
Frank
Manufacturers data for the A277 now in the library
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Now I'm back home from said holiday (all good thing must come to an end), I couldn't wait to have a look at the Ekco.
The cabinet is sound although will require re-finishing at some point. The chassis is in very good condition and just a vacuuming out of dust revealed no corrosion or exposure to damp.
I tested and re-formed the electrolytics and they responded quickly and all are good. There were no obvious faults, so a brief power up revealed that it essentially worked. Low sensitivity and distorted sound plus no magic eye was the order of the day, so let's see why....
To understand the black art of electronics is to understand witchcraft. Andrew.
Well the audio distortion was being caused by a steadily increasing grid voltage on the EL84 output valve due to leakage in C31. That capacitor along with all the other crumbling Hunts capacitors in the set will need to be replaced if the expected performance is to be attained.
To understand the black art of electronics is to understand witchcraft. Andrew.
And after a quick wave of my magic soldering iron.....
The Hunts capacitors along with the defective EM80 magic eye are replaced.
To understand the black art of electronics is to understand witchcraft. Andrew.
The set is now working better, but good audio does not correspond to best tuning as indicated by the magic eye. Obviously, some IF alignment will be required. Not to mention RF likely too.
The screening can for the ECC85 is not fitted....not sure if there should be one there?
To understand the black art of electronics is to understand witchcraft. Andrew.
An interesting looking capacitor fitted in the set was C33, a 220 pf connecting the anode of the EL84 to the tone control. It is a ceramic type, hollow in the middle, and coated in wax. It is rated at 1.75kv. Better quality than a leaky old foil type wax capacitor.
To understand the black art of electronics is to understand witchcraft. Andrew.
A new ECC85 in the front end has brought about an incredible increase in sensitivity. A damp bit of string is almost useable for an aerial now.
To understand the black art of electronics is to understand witchcraft. Andrew.
All going well, Ekco sometimes put a Hunts capacitor in the VHF tuner, if you have not looked maybe worth checking.
IF alignment should be straight forward, you could even get to use the sweep gen you have. ?
I have a similar radio but with VHF, MW and LW AC/DC but very similar valve line up with U series valves. I have it in the utility room with a wire dipole pinned under the upper kitchen unit works very well.
Frank
The set is now working better, but good audio does not correspond to best tuning as indicated by the magic eye.
Have you also checked/changed the electrolytic in the FM ratio detector? Somewhere between 4 and 8uf probably at 50 to 100V working. Common to dry out and difficult to tune a good signal.
You'd be surprised how much of a difference that electrolytic makes to an FM set...
Automatic replacement in my opinion, it’s surprising how high the voltage can get in a valve set, with a simple indoor dipole I have measured 30 odd volts.
Frank
Hi all, thanks for the input....yes indeed there was a Hunt's 0.01uf (c4) decoupler in the VHF can for the ECC85 heater. The ratio detector 8uf 100v capacitor (c29) was tested, reformed, and is fine.
IF and RF alignment was carried out as per the data in the library (thanks Chris) and the chassis is now working brilliantly. Spot on tuning indicator with low distortion audio too. The IF was not a million miles out of alignment, but the ratio detector balance needed careful adjustment. The tuning scale was removed from the cabinet to help with indicating the RF alignment, but this was not too far out. Range is from 87-101.5 MHZ, so classic FM can just be reached, past the racket on Radio 1.
To understand the black art of electronics is to understand witchcraft. Andrew.
IF alignment should be straight forward, you could even get to use the sweep gen you have. ?
Yes, a good candidate for testing the Cossor FM generator with.
To understand the black art of electronics is to understand witchcraft. Andrew.
As this chassis happens to use an EM80 magic eye, I have taken the opportunity to test out my stock of used EM80 eye's. I have about half a dozen, most are still useable, albeit rather dim. I had one or two belts off the flying socket because I was too lazy to turn off the power whilst swapping the eye's. Serves me right really doesn't it.
This one pictured below is a nos Siemens EM80.
To understand the black art of electronics is to understand witchcraft. Andrew.
Today, I have got out the trusty Cossor FM generator and little scope for the sweep. I used the Leader set to exactly 10.7 MHZ to provide the marker frequency pip. I decided to use the diode detector (nice shiny cylinder thing pictured below) that came with the Cossor in place of the EABC80 valve in the Ekco. After some adjustment, I was able to resolve the IF curve. It did not bare much resemblance to the final below trace prior to adjustment of the IF coils. The second trace is with the EABC80 valve re-fitted and looking at the audio output from the ratio detector. In both cases, the marker pip at 10.7 MHZ is exactly in the centre of the scope graticule.
The final results are good sensitivity with improved selectivity, especially noticeable on a couple of closely spaced local FM stations.
It was certainly worth the effort because as reasonably good results were obtained with the peaking of relevant IF coils, a better response can only be obtained by the sweep method.
To understand the black art of electronics is to understand witchcraft. Andrew.
With the electronics all good, the next logical step is to refurbish the cabinet. I have already dismantled where I can parts of the cabinet, the speaker baffle and some decorative trim, ready to be stripped and then re-finished. The cabinet is tatty and there is no other option unfortunately. It is a messy and horrible job but with patience, a good end will result. I hope to use this radio in the lounge when finished, so it has to be presentable ?
To understand the black art of electronics is to understand witchcraft. Andrew.
Today I have been at work on the cabinet. I bought a new tin of Nitromors paint and varnish remover and it is nowhere near as good as it was. Without doubt they have changed the formulation and it is truly awful stuff now. It just leaves a nasty sticky residue that is extremely hard to remove, whereas before, it was easy to peel off with the aid of a wallpaper scraper once it had done it's job in about 5 mins. Now, it has to be left longer and have an additional coat then left for 40 mins. I won't be using this rubbish again. There was a point this afternoon I thought I would never be able to get the darn stuff off of the cabinet.
Anyway, enough moaning and the cabinet is starting to look much better with a first coat of Liberon finishing oil applied. I was lucky with the brass trim, it is solid brass and not some fake brass effect finish on cheap metal. It polished up rather nicely.
To understand the black art of electronics is to understand witchcraft. Andrew.
