10-15-2017, 11:57 PM
Yeah, a tube tester is great, but only if you use it! ;-) I'm embarrassed to admit I have a few Hickoks around, and in fact, a 600A was right there, under not too much stuff (OK, another 70 chassis was on top of it that I was using for reference...)
Since the radio seemed to work at first, I didn't bother to test the tubes, but you can bet I drug the tester out and sure enough, one tube was good but if I tapped it, it would register a short, one was mostly shorted but I could tap it and clear it, and the third one was pretty much always shorted but the lamp would flicker if I tapped it.
Anyway, it was only my self doubt that had me looking under the chassis, and who knew there'd be three tubes with the same short doing the same thing! No wonder my B+ was dropping at different levels! I didn't listen to it much, and in fact when I bought it, I don't think I even let the tubes completely warm up when the guy was trying to demo it for me. He said it was "scratchy" and I knew I was going to recap and clean it.
I'm sure, however, that the B+ issue was not the reason for the addition of the 5.6 Meg resistor.
Maybe it was a workaround for something caused by a leaky capacitor block, which I fixed when I restuffed them all. Also, the two "250K" (240K) resistors at 32 and 25, as well as the "50K" (51K) resistors at 11 and 27 had drifted pretty high, so I replaced them also.
Dan
Since the radio seemed to work at first, I didn't bother to test the tubes, but you can bet I drug the tester out and sure enough, one tube was good but if I tapped it, it would register a short, one was mostly shorted but I could tap it and clear it, and the third one was pretty much always shorted but the lamp would flicker if I tapped it.
Anyway, it was only my self doubt that had me looking under the chassis, and who knew there'd be three tubes with the same short doing the same thing! No wonder my B+ was dropping at different levels! I didn't listen to it much, and in fact when I bought it, I don't think I even let the tubes completely warm up when the guy was trying to demo it for me. He said it was "scratchy" and I knew I was going to recap and clean it.
I'm sure, however, that the B+ issue was not the reason for the addition of the 5.6 Meg resistor.
Maybe it was a workaround for something caused by a leaky capacitor block, which I fixed when I restuffed them all. Also, the two "250K" (240K) resistors at 32 and 25, as well as the "50K" (51K) resistors at 11 and 27 had drifted pretty high, so I replaced them also.
Dan
"Why, the tubes alone are worth more than that!" (Heard at every swap meet. Gets me every time!)
Philcos: 90, 70, 71B, 610, 37-61 40-81, 46-420 Code 121 to name a few.
Plus enough Zeniths, Atwater Kents and others to trip over!
