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Old 03-01-2015, 09:10 PM
legenbass77 legenbass77 is offline
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Join Date: Jan 2011
Posts: 44
Airline 74BR-1510b problem

Hi everybody,

I've been working on a Airline 74BR-1510B for a relative. They said it had been playing, but I don't know how well, and what damage may have been done. When I powered it up on the variable isolation transformer, I could hear it receiving stations, but the familiar 60 hz hum was very pronounced, and didn't change with the volume control, so I proceeded to recap the radio. After a complete recap, it behaves exactly the same way. I've checked everything I can think of, rechecked my work, component values, transformers, volume control, speaker, tubes on my tester, and by substitution. Also checked voltages noting ac, and dc voltages. I compared them to the schematic, and everything was very close to the schematic. I ended up re-stuffing the 40, and 20 mfd multi-section can with a 47, and 22 mfd since there is not much room underneath. 40 is a square, and 20 mfd a triangle, and I wired it back up the same with 47, and 22 mfd modern caps. I did manage to get it turned a different direction, but it's still wired up the same, confirmed with my meter. Also made sure it's isolated from the chassis, and all the negatives are going to B-, not ground. There was also a 27 ohm resistor across pin 2 and 5 of the 35z5 that had gotten hot, and soon crumbled. I replaced it with 22 ohm (all I had in stock) and it's not getting hot anymore after the recap. All other resistors tested in spec. There was also a .15 mfd @400 volt going from the volume control to pin 6 of the 50L6, and it has a ground side that went to pin 6 to the rf choke coil to ground. Printed on the cap is Cornell Dublier, Tiger, .15 MFD, 400 VDC, and a black band with ground. Not quite certain what kind of cap that is, but all I had was a .1 600 volt non polarized replacement. I substituted a 2 mfd electrolytic in, and it made no difference in sound. There aren't too many parts in this chassis, so I didn't think it would be so hard to get going!
As always I appreciate the help!
Attached Images
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File Type: jpg IMG_7244.jpg (94.2 KB, 15 views)
File Type: jpg IMG_7421.jpg (55.1 KB, 12 views)
File Type: jpg IMG_7422.jpg (53.8 KB, 13 views)
File Type: jpg IMG_7424.jpg (119.1 KB, 17 views)
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