22-10-2023, 03:55 PM
Dredging up old radios from the pile of junk awaiting a see-ing to.
Thanks to all who worked out a possibly similar chassis, I can work off the T854,its identical without the tuning eye.
It has become its turn to be assaulted, so on the bench it went.
Seems to be reasonably complete. Missing the output transformer which I think was on the original speaker, the 6X5GT rectifier, and the 6U5G tuning eye. No sign of anything been twiddled. The back and base cards are good. 4 original knobs.
There is a big round replacement speaker badly fixed on one stud and 2 clamps that will need to be better mounted.
The aerial and earth are just a pair of wires hanging out of a smooth hole in the chassis rear flange, no sign of a terminal block or socket.
There seems to be no mounting for the eye, just a right angle bracket screwed to the baffle board. The octal socket is complete with components and wires.
An odd mix of B7G. B9A and octal valves.
Run up with all valves out for an hour proved that the mains transformer is fine. Found a 6X5GT, hung a 6V6 type output transformer on, ( its a 6BW6 output valve ) workshop speaker and aerial connected then run up with all the valves back in produced very little, just an extremely quiet squeak of Radio 4 on what I take to be long wave. So the local oscillator is running and all the valves work.
Moving the aerial to the grid of the mixer produced stations on medium wave and Radio 4 on long wave at fair volume so there was some thing amiss with the front end. Turned out to be broken coils on both the medium and long aerial tuning transformers, they are open, no cans fitted like the short wave transformer, and have presumably suffered over the years.
Very careful removal and inspection found the long wave one broken near the connection to the feed through wire, easily re-soldered but the medium one needed the first 8 turns taken off till I found the break in the Litz wire. Now I have reception, the short wave will not pick anything up on the tiny aerial in the shop but the transformers check out OK so it should work with a decent aerial.
A quick check of the output valve grid showed a positive few volts so the coupling cap was changed along with the HT line decoupling caps, usual leaky waxies. The other waxies are cathode bypass and in minor low voltage places, they all seem to be happy as they are.
The electroytics in the can are fine, running cold.
Now there is good volume, for a while, then massive distortion. The tone corrector cap, a Hunts brown horror, is bubbling. It is 0.002mf 300v AC rated so out with it and in with a 1000v replacement. Still bad sound that faded out to nothing. The output transformer has died! Not surprising, its an ancient one from the reclaimed parts bin. Another restored full and better sound.
So there we are to date. Needs an eye, 6U6G straight sided octal if I can be bothered finding one, a good cleaning, reassembly and another one saved.
Thanks to all who worked out a possibly similar chassis, I can work off the T854,its identical without the tuning eye.
It has become its turn to be assaulted, so on the bench it went.
Seems to be reasonably complete. Missing the output transformer which I think was on the original speaker, the 6X5GT rectifier, and the 6U5G tuning eye. No sign of anything been twiddled. The back and base cards are good. 4 original knobs.
There is a big round replacement speaker badly fixed on one stud and 2 clamps that will need to be better mounted.
The aerial and earth are just a pair of wires hanging out of a smooth hole in the chassis rear flange, no sign of a terminal block or socket.
There seems to be no mounting for the eye, just a right angle bracket screwed to the baffle board. The octal socket is complete with components and wires.
An odd mix of B7G. B9A and octal valves.
Run up with all valves out for an hour proved that the mains transformer is fine. Found a 6X5GT, hung a 6V6 type output transformer on, ( its a 6BW6 output valve ) workshop speaker and aerial connected then run up with all the valves back in produced very little, just an extremely quiet squeak of Radio 4 on what I take to be long wave. So the local oscillator is running and all the valves work.
Moving the aerial to the grid of the mixer produced stations on medium wave and Radio 4 on long wave at fair volume so there was some thing amiss with the front end. Turned out to be broken coils on both the medium and long aerial tuning transformers, they are open, no cans fitted like the short wave transformer, and have presumably suffered over the years.
Very careful removal and inspection found the long wave one broken near the connection to the feed through wire, easily re-soldered but the medium one needed the first 8 turns taken off till I found the break in the Litz wire. Now I have reception, the short wave will not pick anything up on the tiny aerial in the shop but the transformers check out OK so it should work with a decent aerial.
A quick check of the output valve grid showed a positive few volts so the coupling cap was changed along with the HT line decoupling caps, usual leaky waxies. The other waxies are cathode bypass and in minor low voltage places, they all seem to be happy as they are.
The electroytics in the can are fine, running cold.
Now there is good volume, for a while, then massive distortion. The tone corrector cap, a Hunts brown horror, is bubbling. It is 0.002mf 300v AC rated so out with it and in with a 1000v replacement. Still bad sound that faded out to nothing. The output transformer has died! Not surprising, its an ancient one from the reclaimed parts bin. Another restored full and better sound.
So there we are to date. Needs an eye, 6U6G straight sided octal if I can be bothered finding one, a good cleaning, reassembly and another one saved.
Boater Sam.
