29-06-2021, 06:12 PM
I have a few Cossor Melody Makers in their various guises. I found a 494 lying in the junk pile, its the brown Bakelite one with the trim around the speaker and dial painted in cream on the base moulding rather than the later separate plastic trim one that curls up and distorts. The valves are B8G loctals, all present. It has a good case, the back needs a bit or repair around the fixing slots but the frame aerial is still intact on the back panel. Needs a set of knobs otherwise cosmetically its OK, just dirty.
The IF transformers had the usual detached cores, I think this happens because the locking wax runs down to lock the core in the coil rather than just the screws in the tin clips. Mr Twiddler turns the screw and the core falls off the brass screw.
I have tried regluing these in the past without much success so I found another pair of IF transformers, melted off the wax and let all it drip off both adjusting screws to ensure that the cores were not stuck.
Change the audio coupling capacitor to the output valve grid, they are always leaky. Check the output transformer, its good. Fit a new 3 core mains lead because the 2 core fabric and rubber one is not in the best of condition and I like a well earthed chassis.
when there is a mains transformer that will isolate.
Powered up on the lamp limiter, via the bench isolation transformer, I'm not so brave anymore. No drama, just the usual dimming bulb so onto full power keeping an eye on anything cooking up. Now this set has aerial and earth sockets into which the frame aerial on the back panel can be plugged for reception of local stations. But with the back off this is not connected.
Radio restorers will know that these sets have a simple air cored aerial coil with the base connected to the chassis by a capacitor and resistor, not the most sensitive way to tune the aerial but it works reasonably well.
Turning the set on its end to see if anything underneath is getting hot I was surprised to get really good reception of many stations because the aerial coils were now horizontal rather than vertical.
This proved to be better sensitivity wise than with the frame aerial plugged in! Directional of course, as is the back aerial, but it beggars the question of why Cossor needed to fit the frame aerial rather than just mounting the aerial coils horizontally on the chassis?
I wonder what would happen with a large ferrite rod inside the coil?
I set to and cleaned it all up, the fragile printed tuning dial glass was filthy with the 4 rubber corner mounts turned to coal but survived cleaning without losing the print. Found 4 knobs, repaired the back panel and put it all together, another working example of the late 1940s radio sets recovered from the skip.
The IF transformers had the usual detached cores, I think this happens because the locking wax runs down to lock the core in the coil rather than just the screws in the tin clips. Mr Twiddler turns the screw and the core falls off the brass screw.
I have tried regluing these in the past without much success so I found another pair of IF transformers, melted off the wax and let all it drip off both adjusting screws to ensure that the cores were not stuck.
Change the audio coupling capacitor to the output valve grid, they are always leaky. Check the output transformer, its good. Fit a new 3 core mains lead because the 2 core fabric and rubber one is not in the best of condition and I like a well earthed chassis.
when there is a mains transformer that will isolate.
Powered up on the lamp limiter, via the bench isolation transformer, I'm not so brave anymore. No drama, just the usual dimming bulb so onto full power keeping an eye on anything cooking up. Now this set has aerial and earth sockets into which the frame aerial on the back panel can be plugged for reception of local stations. But with the back off this is not connected.
Radio restorers will know that these sets have a simple air cored aerial coil with the base connected to the chassis by a capacitor and resistor, not the most sensitive way to tune the aerial but it works reasonably well.
Turning the set on its end to see if anything underneath is getting hot I was surprised to get really good reception of many stations because the aerial coils were now horizontal rather than vertical.
This proved to be better sensitivity wise than with the frame aerial plugged in! Directional of course, as is the back aerial, but it beggars the question of why Cossor needed to fit the frame aerial rather than just mounting the aerial coils horizontally on the chassis?
I wonder what would happen with a large ferrite rod inside the coil?
I set to and cleaned it all up, the fragile printed tuning dial glass was filthy with the 4 rubber corner mounts turned to coal but survived cleaning without losing the print. Found 4 knobs, repaired the back panel and put it all together, another working example of the late 1940s radio sets recovered from the skip.
Boater Sam.