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Well...got the coils back into the chassis last night. I can now listen to all kinds of static. The unit still will not obtain any stations. I do have a small AM broadcaster that I can broadcast on (3) different frequency's. If I get the transmitter antenna close enough to the IF (44) Control Grid, I get that station. I went back in to check some voltages again. It seems like my plate voltages and Screen Grid voltages are all a bit low. What should be 230-240 on the plate, is really more like 157. Same on the Screen Grid. What should be 90 is more like 55.
On another note, my amplifier stage is all working fine and dandy. Any suggestions??
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Tom,
Great job rewinding the coils!
If the plate and screen voltages of the RF (44) and the Det/Oscillator (36) tubes are low, you probably have resistors that need to be replaced.
The resistor that will affect the plates of the 44 and 36 tubes is component #20. This should measure 5000 ohms. Many resistors drift high over the years, so check that resistor (and probably replace it if it is more than about 10% high).
The screen voltages of these tubes are controlled by the resistor divider composed of components #47 and #48. These should measure 51K and 39K ohms respectively. If either, or both, of these resistors have drifted significantly, the screen voltage will be affected. You probably need to replace these as well.
Good luck
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Finally got all of the resistors replaced. Even if they weren't out of tolerance, I replaced them. I'm still having the low voltage issues. I'm about to pull my hair out on this one. I also changed the electrolytic caps back to 6.8mf instead of the 10mf that I originally installed when I first got the beast. I knew it wouldn't change anything. I just wanted to get it as close to original as I could. Its a good thing I have my kegerator close to my bench!
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So here are some readings I am getting. I am still looking for some help on this thing.
My rectifier filament voltage is correct @ 5v. The rest of the filament voltages are also correct @6.4v. Plate voltages at my rectifier is @360v. So my power transformer voltages are right where they need to be. As I had stated before, All resistors and caps have been replaced with new. I have gone through the wiring lead by lead and everything is correct.
According to Riders V3-Philco 3-34, I should be reading 230-240 volts on my plates. I am actually reading about 150v. I should be reading 90 from K to SG, and I am getting 55v. What in the world am I doing wrong??
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Eureka!!! Kind of. I pulled one tube at a time and re-energized the chassis. I found that if I remove the output tube (42), the voltages go up to where they need to be. I threw the 42 into my tester (Precision 612), and it tests fine. Any ideas??
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Sounds like the bias may be off on the 42 tube and its drawing to much current. With the tube installed and the radio powered up check the voltage from pin 4 to ground and let us know what that reading is.
Gregb
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Looks like it is 8.6 volts
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Seems a little low, should be around 15 volts. Check resistor #43, the large wire wound unit. Off the top of my head I don't recall the values and can't read it on my poor copy of the schematic, sorry. The 42 tube is the one tube that consumes the most current in the radio so the bias needs to be correct or it will upset the whole set.
Gregb
(This post was last modified: 03-02-2019, 06:38 PM by
gregb.)
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Resistor #43 is supposed to read 32 ohms and 232 ohms. Actual readings are 33.5 ohms & 240 ohms. Could I remove one of the windings on the 240 ohm part to get it closer to the 232?
(This post was last modified: 03-02-2019, 07:26 PM by
tkibler.)
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No, that is plenty close enough. Do you have another 42 to try, a gassy tube can cause this issue.
Gregb
(This post was last modified: 03-02-2019, 08:30 PM by
gregb.)
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I'm going to order one tonight. Stay tuned. Thanks for all the help!!
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Okay guys...I actually had a NOS #42 Output tube in my stock. I found it after I ordered another one
. Voltages read the same when the 42 is inserted. Strangely enough, when I read the voltages with the 42 out of the equation, my voltages actually seem to be too high. Here is what I get with the 42 pulled...Is this normal?
#44 (RF) Plate=322v SG=140
#35 (Det) Plate 290v SG=110
#44 (IF) Plate=335 SG=139
#75 (2nd Det) Plate=180
So I removed power, plugged the 42 back in. I put my meter across P to K on the 44(RF) tube. Tuned the beast on. Voltage read 322 for a few seconds then quickly dropped down to 160v. I know the 42 is good. What in the world is going on.
One more tidbit that I found. The speaker that came with this doesn't seem to be original. The field coil is actually around 5k ohms instead of the 1.1k ohms it should be. The voice coil is a bit low as well. It is about 300 Ohms. Doesn't seem like that would affect the voltages though.
Tom
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The 5K field will definitely affect voltages (almost 5X what it should be, so no wonder B+ is low). A 300 ohm voice coil? Are you sure? That won't affect voltages but will affect volume of your radio.
Your 89 was designed for a speaker with an 1100 ohm field and a roughly 1 ohm voice coil.
--
Ron Ramirez
Ferdinand IN
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+1
That field coil will be an issue for sure.
Gregb
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Okay. So let me start the search for a new speaker. It a bummer because I had this one re-cone too. It wasnt the voice coil that was 300. It was the primary side of the transformer that feeds the voice coil. I wasnt very descriptive.
