Thread: Ekco A455
View Single Post
Old 12th Sep 2018, 4:18 pm   #1
Mach One
Mach One's Avatar
Join Date: Sep 2005
Location: Shoreham-by-Sea, West Sussex, UK.
Posts: 457
Default Ekco A455

I use the word "Success" because it is a personal success for me rather than it matches up to the standard of the superb quality refurbishments that we have in this section from time to time. Success is relative...

I bought this radio on a certain auction website around ten years ago. I bought it for two reasons: (1) It has Radio Caroline marked on the scale and (2) it's a transistor radio that still thinks it's a valve set. It has sat firstly as a curiosity in our lounge for half that time and more recently in a plastic box in the loft. I have finally got around to doing something about the various radios that I have been storing there and lining up for refurbishment and this is the second one, actually. It's the first one that is totally finished (as far as I am concerned, that is...).

First things first - I knew that it worked - kind of. But the dial pointer would get stuck on its travels across the dial. I assumed that it might need re-stringing but I was wrong. What I actually found was that the three rubber mountings on the main tuning capacitor were thoroughly perished and the poor capacitor was hanging on by a thread - literally. The dial cord was being pulled out of line and slipping off the large rotary metal "gear" which turns the capacitor.

This almost stopped me in my tracks. But, as I have found in the past, go off and do something else and sometimes a stroke of genius brings a solution to mind. My inspiration was to use one of the fake wine corks that I have been storing in said loft for some miscellaneous purpose and a small amount of coaxial cable outer casing to manufacture something similar which will mount and insulate the capacitor from the chassis in the same way that those old rubber grommets had been doing for fifty years previously. It doesn't look pretty (as you can see from the photograph) but it worked well and after re-stringing (actually just slipping the old string back into place) the dial was working.

Flushed and very relieved with this success I went on to have a look at the circuitry. I checked the values of the resistors and found that some of them were definitely rather higher than they should be. When I switched the set back on and attempted to measure voltages I must have touched / knocked something because the previously working set suddenly went silent - except for a tell-tale 100Hz hum. "That's blown it," I thought - thinking specifically of the germanium output transistors...

Interestingly, when I unscrewed the amplifier board and transistors from the chassis the set then went on to work again. I discovered that I could measure a voltage from at least one of the cases of the transistors with respect to (+ve) earth So, I decided to try and replace them. Along with this I also decided to replace all the resistors and most of the capacitors at the same time - mostly for fun (!).

Over the period of about six weeks I unsoldered the old components and soldered in all the new ones. I took one liberty with the component values: The output capacitor was stated as being 250F. I knew from my boyhood experience that a value of this small size would seriously reduce what bass response that there might be and took the decision to fit one of 1000F. I'm glad I did - the set sounds quite a bit better in my opinion. Not quite valve set standard but better than most modern transistor sets.

So with all this done, it was time to switch the set on - it worked (!) - and align the RF section and re-fit into the case. I decided not to worry about the cosmetic condition of the set as I know what I am like and do not think that I would be able to successfully make it look like new. I don't mind a set looking old but do mind when it doesn't work!

A couple of notes on the design of the set: I have never come across a set with transistors in it - never lone Germanium - that has such a high "HT". 24v! As I said, it's a transistor set that still thinks it's a valve set which amuses me, I'm afraid. I think that the standard of construction is really quite poor but I'm pleased with it for its quirks. I hope that you find this at least some way interesting!

Pictures (hopefully self-explanatory) attached...
Attached Thumbnails
Click image for larger version

Name:	1.jpg
Views:	136
Size:	148.0 KB
ID:	169198   Click image for larger version

Name:	2.jpg
Views:	158
Size:	195.2 KB
ID:	169199   Click image for larger version

Name:	3.jpg
Views:	152
Size:	101.1 KB
ID:	169200  
Mach One is offline