Cossor 569 LW + MW transistor radio 1958

1958 was the year most UK radio makers decided to give the transistor design a go. This was an early Cossor design that differs in only one way from the others, the carry handle is transparent with radio station names and frequencies have been printed due to lack of space on the small tuning dial. The tuning also employs a slow motion drive for ease of tune. All metal fittings were gold plated and even the speaker cloth has gold braid woven in the weave, making it glitter in certain lighting.  A.C. Cossor Ltd. was a British electronics company founded in 1859. The company's products included valves, radios, televisions and military electronics. The company was purchased by Raytheon in 1961.
the repair

Where do I start? this was a proper 'car crash' of a radio, but at least it was complete. The rear removes with just a pull on the cloth tap and pulls away tidy. Inside I found a strange battery box with actual battery's printed on the outside so you could copy the direction of insertion. The two plastic ends were loose and I presume a rubber belt held then against the box  It holds 6 small torch batteries giving 9 volts and is centre tapped to the speaker, quite common in the early days of radio. I decided to strip the whole thing down for cleaning and essential repair.

I've added full service info. published in a book I have from 1959

This involves removing the chassis (circuit board) from the cabinet and removing all loose parts on the cabinet for cleaning; speaker logo badge, carry handle etc. With all this removed cabinet repairs can be done much easier, followed by electrical stuff later (or before, depends what mood i'm in) . On this occasion I decided on an electrical repair first, the tuning control was seized-up and the knobs had been glued on and too a very long time to remove without breaking.

arrows show where ball bearings were missing

With  rear screw and nut removed 2 sections part company, 3 balls for travel and one centre ball was used

Lost grub screws are not a good enough reason to glue a knob in place. 4 BA bolt can be cut to size and a screwdriver slot sawed into one end, use soft steel bolts, easier to saw. Because the knob was glued in place a later repair person had tried to pull knob off spindle and broke the tuning capacitor bearings. So I removed the tuning capacitor for examination, just 4 terminals on the print, 2 earths and two RF and OSC tuning. Once removed I could see that a couple of ball-bearings were missing at the rear end of the unit. I found one larger one that fitted in the centre and held it ion place fine. A fixing nut and a screw hold the whole thing in place. The adjusting screw aligns the air gap between the tuning veins, good glassed needed for this job. Finding another tuning capacitor is not really an option here. I robbed the ball-bearing out of a similar capacitor I had brought in a clear-out sale. The glue had seized-up the fine tune spindle and I removed most of it with a pin head and some oil.

Arrow shows rear of jammed spindle

Arrow shows front of jammed spindle

The next job was to un-jam the volume control, this was stuck hard against the wave change switch and I had to remove them both to get a good grip on the control and use lock wrenches to twist spindle free. Even then it was still stiff, I finished of with some graphite power that Lock Smiths use to un-jam door locks. I had to remove lots of aerial coil wires to remove the controls, so took lots of good photos to refer to for re-assemble later.

I soldered a couple of mobile phone battery's to temporally power the set up (4.5v) It started to work but then went very quiet and that was found to be an 8 uF (C21) coupling capacitor from the volume control to the audio amp, I fitted a 10 uF. The chassis was now ready for it's cabinet, so next job was the clean all the outer parts of the set. First were the control knobs, when they became loose the gold paint had rubbed away from  underneath.

Causing almost no audio C21 and 8uF found connected to slider of volume control to first audio amp.

I didn't have any gold paint but I decided to uses some gold card instead and this would also reduce the friction between the knobs and the cabinet in the future. Knobs were cleaned with a toothbrush and Fairy Liquid in the sink, knob ousters were glued back in place and two grub screws for the knobs were made (described earlier)

It was useful to know witch wires from the aerial coils when to which switch (Aerial arrives at L1)

The Cossor name plate from the front was removed and cleaned, 3 bendy pins hold it in place (One under the speaker) Paint spill underneath was removed with paint stripper and cabinet cleaned with toothbrush and soap then spray polish applied to give it a sheen. The carry handle is only loosely fitted so I added two rubber washers each side, some of the gold paint was missing, that a job for another day. This was a tricky job but it was all done in a day, that's way more time than it's worth, but it's better than watching the Box.