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Airline Rudolph 05gcb-1540

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Post by Rickey on Wed Oct 12, 2011 7:16 am

I have recapped the electrolytics in this radio. At first I had no audio, then I jumpered it to another radios speaker/transformer, then I got a low hum. It has a resistor looking part that I think is a cap. Should I change it out? The tubes are hard to get to to check voltages. The transformer did show like 1.875k on the input and almost zero on the output, tested still in radio. Thanks
Airline Rudolph 05gcb-1540 Th_ca7b8105
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Post by Rickey on Wed Oct 12, 2011 7:19 am

Here is a better view of the big "resistor"!
Airline Rudolph 05gcb-1540 Th_fb063713
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Post by Resistance is Futile on Wed Oct 12, 2011 3:45 pm

Thats a resistor 47 ohm 2 watt
http://sparks-radio-shack.forumotion.com/t144-rudolph-airline-05gcb-1540
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Post by Rickey on Wed Oct 12, 2011 5:50 pm

Thanks RIF, it's a whopper!
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Post by Rickey on Wed Oct 12, 2011 5:52 pm

I put another transformer on it and replaced all the other caps. I think the one that got the audio tranny was the mica mold! It's singing like a bird now! I mean a reindeer!
Thanks, I truly love the forum!
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Post by Rickey on Wed Oct 12, 2011 5:53 pm

Here it is recapped
Airline Rudolph 05gcb-1540 Th_0ca6daa2
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Post by Rickey on Wed Oct 12, 2011 5:54 pm

Here are the bad guys!Airline Rudolph 05gcb-1540 Th_e7faebe6
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Post by Rickey on Thu Oct 13, 2011 8:38 pm

Thanks Bill, more to follow!
Shocked
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Post by Rickey on Thu Oct 20, 2011 3:50 pm

After a couple of days I get distortion on this set.Now i have some voltages. The cathode on the 50c5 reads 5 volts dc. The cathode resistor reads 190, a little out of the 20 percent range, should be 150. I get low positive voltage on the grid pin ,1.2 volts. I should be on dc, correct? The radio improves vastly when i check the voltage on the cathode!
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Post by Rickey on Thu Oct 20, 2011 3:54 pm

the resistors are beyond 20 percent in a couple of cases(30) percent.
Resistor 3 should be a 10 meg and it reads 17 meg! its on the 12at6 on pins 1 and 2, grid and cathode. I ordered a few resistors from mouser, but i dont think i ordered the 10 meg.Would this resistor cause distortion?
Thanks,Rickey
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Post by Bill Cahill on Thu Oct 20, 2011 5:18 pm

I don't know what you mean by distortion, but, it would cause issues with sensitivity.
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Post by Rickey on Thu Oct 20, 2011 5:45 pm

The radio sounds like a bad filter capacitor, but they are ok!
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Post by Bill Cahill on Thu Oct 20, 2011 6:11 pm

Also, on pin 2 of 50C5 you should get low negative, or 0 volts.
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Post by Rickey on Fri Oct 21, 2011 12:46 pm

All caps were changed to begin with. I get very low positive volts on pin 2. The audio tube gets hotter than a 2 dollar pistol! The dial light glows very dim also?
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Post by Bill Cahill on Fri Oct 21, 2011 4:51 pm

That tube cannot have any positive voltage there. It's going to dammage the tube. Sounds like radio is also drawing too much current.
Have you got pictures of your work?
Show what you connected there.
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Post by Wildcat445 on Fri Oct 21, 2011 11:29 pm

check the 50C5 for grid emissions. The coupling cap goes to the grid. If I understand you, there is positive voltage there. And that the radio played well for awhile and then went bad. Grid emissions usually occur after the tube gets hot. This has bitten me more than once and is tough to detect. Change the 50C5 and see what happens. I actually had this happen to me last week. With the 12BA6 IF tube. I had never seen that before. Caused distortion just like an output tube would. Ever seen this, Bill?. Just for my own clarification, what is your B+ voltage at the rectifier cathode. That reading would tell you if something is drawing too much current, or if you have a weak rectifier or all or none of the above! The dim dial lamp ( assuming its the correct one) being dim concerns me, too.......... Crying or Very sad

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Post by Rickey on Sat Oct 22, 2011 11:38 am

Thanks guys, I will post the rectifier voltages later.
Yes, the radio was playing great after I put in all new caps , then the distortion/hum showed up.
Airline Rudolph 05gcb-1540 0ca6daa2
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Post by Rickey on Mon Oct 24, 2011 7:32 am

Ok, I changed a few, out of range resistors. The radio started playing better when I changed the 10meg out. I still get positive voltage on pin 1 of 50c5. I am going to try a few different tubes and measure again. I changed the 6.8 Meg resistor also. I think it improved the most when I replaced it.
Thanks, Rickey
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Post by Rickey on Thu Oct 27, 2011 7:52 am

Radio playing great now. The resistors did the trick!
Thanks!
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Post by Rickey on Wed Nov 09, 2011 6:56 pm

Rudolph is playing and looking great! I need ideas on filling in the letters on the label. Thanks for all the help!
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Post by Motorola man on Wed Nov 09, 2011 7:09 pm

A fine paint brush and a very steady hand. rendeer
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