28-10-2016, 07:04 PM
Now I don't usually struggle with a radio, but, this one is being difficult.
Tried to rejuvenate the Hunts 16 - 32uf can, got to 4mA then it started warming and creeping up, so cut it and emptied it. Plenty of empty space around the sweated core, stuck in tar at the bottom, not connected to the can at all despite it saying "can not isolated". Drilled holes for wires in the 3 tag rivets and fitted 20uf & 100uf that were at hand. Put it back with the cut in the clamp, invisible repair.
Found an open circuit medium wave coil, managed to pick up the end and fixed it. Strange because it worked as it was on medium wave!
Changed the long wave oscillator coil shunt cap. 100pf gone to 23pf, checked all the trimmers for shorts, replaced the triode grid cap, cleaned the wave switch. Tried padding the long wave coil to see if it was just miles out of tune as the ferrites are in bits glued together. All coils are intact and no shorts to ground.
DMM on the triode grid kills the oscillator on all bands, so it may be a scope job.
Its fine on medium and short waves but long is just hash getting more strident at the high frequency end. Aerial on the mixer grid gives the same results. Its got to be in the oscillator coils somewhere, but where?
Out of my 11 EF39s only 2 work, the rest go unstable and its not due to the metallising not earthing.
Its not decouplers either, I just have no luck with EF39s, may move to 6K7Gs.
So if anyone has any ideas, please shout up.
Tried to rejuvenate the Hunts 16 - 32uf can, got to 4mA then it started warming and creeping up, so cut it and emptied it. Plenty of empty space around the sweated core, stuck in tar at the bottom, not connected to the can at all despite it saying "can not isolated". Drilled holes for wires in the 3 tag rivets and fitted 20uf & 100uf that were at hand. Put it back with the cut in the clamp, invisible repair.
Found an open circuit medium wave coil, managed to pick up the end and fixed it. Strange because it worked as it was on medium wave!
Changed the long wave oscillator coil shunt cap. 100pf gone to 23pf, checked all the trimmers for shorts, replaced the triode grid cap, cleaned the wave switch. Tried padding the long wave coil to see if it was just miles out of tune as the ferrites are in bits glued together. All coils are intact and no shorts to ground.
DMM on the triode grid kills the oscillator on all bands, so it may be a scope job.
Its fine on medium and short waves but long is just hash getting more strident at the high frequency end. Aerial on the mixer grid gives the same results. Its got to be in the oscillator coils somewhere, but where?
Out of my 11 EF39s only 2 work, the rest go unstable and its not due to the metallising not earthing.
Its not decouplers either, I just have no luck with EF39s, may move to 6K7Gs.
So if anyone has any ideas, please shout up.
Boater Sam.
