Thomas
I have a H500 that has absolutely no reception. I have replaced the filter caps,and the black beauty caps. The tubes check fine and I have replaced the selenium rectifier with a 1n4007 diode and a 47 ohm 5 watt resistor. The tube voltages check very close to the schematic except the 1l6 filament voltage is 1.25 volts and I understand that this filament should be closer to 1.4 volts for proper operation. I have rechecked my connections on the replaced items and they all look fine. There is no noise coming from the speaker at all any ideas? Thanks!
Did you check to see that the output transformer isn't blown or that the tone condenser is not shorted? Is the plate of the output tube receiving its proper voltage? If not, then your output transformer primary is open. You don't get any hum or noises of any kind from the speaker?
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:Thomas
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:I have a H500 that has absolutely no reception. I have replaced the filter caps,and the black beauty caps. The tubes check fine and I have replaced the selenium rectifier with a 1n4007 diode and a 47 ohm 5 watt resistor. The tube voltages check very close to the schematic except the 1l6 filament voltage is 1.25 volts and I understand that this filament should be closer to 1.4 volts for proper operation. I have rechecked my connections on the replaced items and they all look fine. There is no noise coming from the speaker at all any ideas? Thanks!
I've never owned a radio with that darned 1L6 tube everyone talks about. I have radios with a 1LA6 tube--this is a loctal heptode with the old style circuit--second grid is not tied to any other grids. When this tube gets weak, it causes all sorts of spurratic operation--stations stay synchronized, but radio will sometimes break into a squeal and then go dead (oscillation).
When you tune the radio through the portion that it does tune, are the stations synchronized with the markings on the dial? If they are not synchronized, your radio could be out of tune (IF transformers and oscillator/antenna circuit). The standard broadcast doesn't really have anything much below about 540 kilocycles, so if your radio is really out of tune, and it's getting 540 kilocycles up at the 1200 kilocycle region, then that would explain why you don't get anything below this. However, I don't know how your radio could be this much out of alignment and still pick up stations properly. Usually the radio will not function with a frequency shift of this severity--perhaps it could. It is also possible, if the frequencies are actually shifted like stated above, that a condenser has opened up (such as one on the oscillator coil), or that a condenser was replaced at one time with a wrong value unit. Actually, if a condenser on the oscillator coil (especially if it is connected across the primary) was replaced with a higher value condenser, this would bring the low end of the dial way up high, and the radio would probably work just fine. Before making these last assumptions, it is very wise to first go over the trimmers on the IF transformers and the oscillator and antenna circuits, using a good signal generator.
If, however, your radio tunes in a synchronized manner over the section it does tune, then I'd check for a weak oscillator tube (1L6) or perhaps that low filament voltage. I highly doubt that the 1.2 volt supply will cause any trouble, though. Usually these tubes perform well when the voltage has only deviated down that little. Perhaps a resistor on the 1L6 has drifted high, causing the tube to perform sloppily.
Before changing all sorts of components around, though, it is best to test the tubes, and then test the set with a good signal generator. After that, test components in that section with your multi-meter. Don't replace components unless they're bad. Also, be sure that the B voltages are where they should be (generally the plates of most tubes except the first audio will be around 70 volts, perhaps 90, though all my Zeniths use 70).
Thomas
:Thanks for the info. I did find that one wire of the speaker had a bad solder, once I fixed it the radio began to somewhat work. The new problem is that reception is weak not very bad but weak nevertheless, also the radio only picks up stations from 1200-1600kcs broadcast band and a few very faint shortwave stations on 4-8mcs. Any ideas?
:
:Did you check to see that the output transformer isn't blown or that the tone condenser is not shorted? Is the plate of the output tube receiving its proper voltage? If not, then your output transformer primary is open. You don't get any hum or noises of any kind from the speaker?
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::Thomas
::
::I have a H500 that has absolutely no reception. I have replaced the filter caps,and the black beauty caps. The tubes check fine and I have replaced the selenium rectifier with a 1n4007 diode and a 47 ohm 5 watt resistor. The tube voltages check very close to the schematic except the 1l6 filament voltage is 1.25 volts and I understand that this filament should be closer to 1.4 volts for proper operation. I have rechecked my connections on the replaced items and they all look fine. There is no noise coming from the speaker at all any ideas? Thanks!