06-11-2017, 08:09 PM
Any ideas ? It is playing up and down the dial, but with low volume. Please consider the following facts:
1) the voltages at the tube sockets all look good, perhaps a bit high (e.g. 187 on the plate of the 1st RF tube, 275 on the plates of the '47 tubes);
2) Both '47 tubes are good and test the same
3) All of the other tubes have been tested and are at or above the reading showing on the roll chart of my Hickok
4) The plate voltage at the 1st Audio Tube is just 89. Bypassing Resistor Number 46 increases it to 138V, but with no increase in volume.
5) Jumping the volume control makes no difference from setting the volume control at maximum
6) All fixed capacitors, except a few mica units which test properly, were replaced
7) The audio inter-stage transformer primary measures something in the 4.5K range, and the secondary something like 5.5K ohms.
It took me too long to finally determine that one of the capacitors numbered 25 on the schematic was missing. It only worked at the low end of the dial, and RF alignment was impossible. Both number 25 were originally metal cans, long gone from this chassis.
By the way, the schematic notes that there are two capacitors numbered 34, but that is incorrect.
1) the voltages at the tube sockets all look good, perhaps a bit high (e.g. 187 on the plate of the 1st RF tube, 275 on the plates of the '47 tubes);
2) Both '47 tubes are good and test the same
3) All of the other tubes have been tested and are at or above the reading showing on the roll chart of my Hickok
4) The plate voltage at the 1st Audio Tube is just 89. Bypassing Resistor Number 46 increases it to 138V, but with no increase in volume.
5) Jumping the volume control makes no difference from setting the volume control at maximum
6) All fixed capacitors, except a few mica units which test properly, were replaced
7) The audio inter-stage transformer primary measures something in the 4.5K range, and the secondary something like 5.5K ohms.
It took me too long to finally determine that one of the capacitors numbered 25 on the schematic was missing. It only worked at the low end of the dial, and RF alignment was impossible. Both number 25 were originally metal cans, long gone from this chassis.
By the way, the schematic notes that there are two capacitors numbered 34, but that is incorrect.
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