02-06-2023, 11:51 AM
Can we see what the "new model" A-K 35 looks like and where it is located during testing?
FWIW although the binocular coils have a confined RF field any metal closer than an inch can effect them. It could be that a metal bench, insulated, yet metal could be effecting the radio. Yes, I know the 35 has a metal can cabinet. I have one in my collection too. Place a block of wood or panel under the radio.
Try: Removing the bands from the tuners and tune each independently, if there is a tracking problem independent tuning will solve it. If the bands are too tight, the rotor of the outside tuners can be pulled out of the cone bearings. Obviously if your model has two bearings in each tuner then that is moot.
Keep the B+ for the detector at the rated voltage, be sure the two bias resistors across the "A" supply that are used to obtain a bias for the detector grid are in the right order or the bias will be wrong. The detector works because the tube is set up to operate in a non-linear mode, it detects at the plate as well as amplifies. If the values of the external circuits for the detector are wrong detection will be weak or non-existent.
Be mindful of that ground "loop" caused by the A- and that the A- is not connected to ground via the power supply ALSO! that the antenna is NOT grounded at the far end too.
The 201a is a rugged tube and can recover if paralyzed by a rejuvenation process. They won't last forever in use as the thorium is eventually depleted from the interior of the tungsten wire. Using the 201a outside of its normal operation does deplete the surface thorium layer faster than it can be replenished at normal operating temperature (voltage).
Radio fans of the 20's would ever so often do a "low level" rejuvenation by removing the B & C batteries such that no potential is on the plate or the grids. Then, fully charge the 6 volt L/A battery, of of charge a L/A 6-volt battery is 6.6 volts. Then, turn on the radio and turn up the rheostats so all resistance is removed and allow the filaments to burn for 1/2 an hour. Thus process works so long as there are no fixed dropping resistors in the radio or automatic filament ballasts. For those radio fans with that type of radio one had to invest in a "Tube Rejuvenator" or combined rejuvenator/tester (plate current meter)...
I often wondered why the ends of battery radio power cables were so frayed
Keep trying all the suggestions made. The problems will soon be discovered...
GL
Chas
FWIW although the binocular coils have a confined RF field any metal closer than an inch can effect them. It could be that a metal bench, insulated, yet metal could be effecting the radio. Yes, I know the 35 has a metal can cabinet. I have one in my collection too. Place a block of wood or panel under the radio.
Try: Removing the bands from the tuners and tune each independently, if there is a tracking problem independent tuning will solve it. If the bands are too tight, the rotor of the outside tuners can be pulled out of the cone bearings. Obviously if your model has two bearings in each tuner then that is moot.
Keep the B+ for the detector at the rated voltage, be sure the two bias resistors across the "A" supply that are used to obtain a bias for the detector grid are in the right order or the bias will be wrong. The detector works because the tube is set up to operate in a non-linear mode, it detects at the plate as well as amplifies. If the values of the external circuits for the detector are wrong detection will be weak or non-existent.
Be mindful of that ground "loop" caused by the A- and that the A- is not connected to ground via the power supply ALSO! that the antenna is NOT grounded at the far end too.
The 201a is a rugged tube and can recover if paralyzed by a rejuvenation process. They won't last forever in use as the thorium is eventually depleted from the interior of the tungsten wire. Using the 201a outside of its normal operation does deplete the surface thorium layer faster than it can be replenished at normal operating temperature (voltage).
Radio fans of the 20's would ever so often do a "low level" rejuvenation by removing the B & C batteries such that no potential is on the plate or the grids. Then, fully charge the 6 volt L/A battery, of of charge a L/A 6-volt battery is 6.6 volts. Then, turn on the radio and turn up the rheostats so all resistance is removed and allow the filaments to burn for 1/2 an hour. Thus process works so long as there are no fixed dropping resistors in the radio or automatic filament ballasts. For those radio fans with that type of radio one had to invest in a "Tube Rejuvenator" or combined rejuvenator/tester (plate current meter)...
I often wondered why the ends of battery radio power cables were so frayed
Keep trying all the suggestions made. The problems will soon be discovered...
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
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