It has five bands covering 550 kHz to 30 MHz. It's quite heavy for a battery radio, but seems to be very well built.
This has just come off my workbench, so before it goes back to its owner I thought I'd put a picture and a few words about the repair on here.
This EC10 belongs to my mate Jonathan, who took it off the shelf where it has sat for a few years and found that it didn't work anymore. All of the radios that I have worked on recently have been valve (tube) based, so this was a good opportunity to fault find on something with transistors.
I was half expecting that the transistors might be the problem. Many of the devices produced in the 1960's (and possibly later) had tin plated cases which, it is now known, turned out to be a serious design flaw. Tin has some strange properties and over the years crystalline 'whiskers' can grow like stalactites inside the case, eventually shorting out the internals of the transistor. Even so-called new old stock (NOS) transistors can be faulty for this reason, even though they have never been used. When good tested transistors appear on the auction sites they often sell for silly prices. One seller I found was asking £15 for one OC171 transistor, and there are six of them in this radio!
When I switched this radio on it was obvious that it was pretty 'deaf'. The only thing I could pick up, even with an external aerial, was the local Gold AM station on 1332 kHz and that was extremely weak. I'm less than 5 miles from the local broadcast transmitter so obviously the radio was suffering from very poor sensitivity! It also had a 'rushing' noise from the loudspeaker which didn't change in level when the volume was twiddled. The band change switch was also very noisy when operated.
I decided to change all the old electrolytic capacitors first. Some repairers like to leave these as original and only change those that prove to be faulty. In my experience many or all of them will prove to be duff, and much time and frustration can be saved by applying what some have called the 'shotgun approach'. At only a few pennies each its cheap enough to change them all in one go. Many modern capacitors are of a similar size to those used in old transistor sets, and they can be fitted without looking too much out of place.
After changing all the old capacitors I started looking for the source of the noise. A bit of simple fault finding pointed to a noisy 180K resistor in the driver stage. After replacement the noise hadn't gone away completely, but I thought it was reduced to an acceptable level.
Next, I decided to take a can of switch cleaner to the wafer switches. There are six of these, ganged together on the shaft turned by the Band Change knob. After giving these a good cleaning I plugged the aerial back in and suddenly loads of signals came pouring in.
A fairly simple repair then, but I'm quite pleased with the result. The receiver seems quite sensitive, and definitely better than my workshop Ekco valve radio. The audio quality is a bit harsh though and I would probably find listening to music on a bit tiresome after a while, but in fairness as a communications receiver this isn't what it was designed for.
Its a real pity that so many of the interesting short wave stations have closed down and there is much less to listen to these days. I reckon owning one of these sets in years gone by would could have been a lot of fun!
The workbench is now free for me to finish my Wartime Civilian Receiver rebuild. More about that coming soon.
Keep listening!
