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I'm working on a Philco 46-1226. I replaced all the tubes except the 7AF7 and 6J5GT. They were on backorder and the current ones in the unit appear to be working, but I'm not sure they are at full power. When I turn the radio on I can only receive one station (powerful one in Albuquerque) and I'm experiencing feedback and a humming sound. Also two of the tubes (both are the 6K6GT) become very hot - is this normal?
Any suggestions on the why I'm only picking up one station and getting the humming sound?
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If the majority of the capacitors have not been replaced then it time to do that.
Hot AF output tubes are a sign of incorrect bias. Check C32, 33, 34 for leakage, C36 and the dual C37. Confirm the value of R30 and its connection to the chassis. That causes a high plate current and overloads the power supply so it begins to hum, the caps in the supply cannot make up for the high current flow so 120hz ripple results. The 6K6 can be permanently damaged if it is severely overloaded, emissive material will get deposited on G1 and the tube will loose control over the plate current. YMMV chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
(This post was last modified: 02-17-2021, 01:12 PM by
Chas.)
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Welcome to the Phorum!
I moved your thread into the Electronic Restoration section
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Are the capacitors available at most electronic supply stores or are they unique to the era the radio was made? In other words, can I buy these at my local electronics supply store?
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It depends. Most modern electronics use low voltage parts where vacuum tube stuff use parts need parts that are in the 400-600v range.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
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I followed everyone's advise on my radio and it is working great. Now I'm on to the record player in the 46-1226. The record player is rotating but I'm not getting any sound so I'm assuming I need to replace the needle cartridge. My understanding is the needle for these units is no longer available. Does anybody have a suggestion on suitable replacement and where to buy it?
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A needle replacement depends on the cartridge. And if the cartridge is a crystal cartridge then it most certainly will not produce any music. The crystal is probably dried up. I replaced a crystal cartridge with a ceramic one from Voice of Music:
https://www.thevoiceofmusic.com/catalog/...es=Crystal
They have other cartridge options and needles.
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Rick
With the turntable cable unplugged and the volume reduced half-way (so not to blow the cone out) touch the cartridge's pins one by one: the one that is not GND should produce the loud hum.
If it does - this verifies your cartridge is dead or at least not doing its job.
If it does not, then see to it that it does first.
Oh
http://www.nostalgiaair.org/pagesbymodel...013588.pdf
This is 46-1226 sch. Somehow it does not show the tube you referred to, the 7AF7.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 04-19-2021, 08:46 PM by
morzh.)
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Thanks for the information.
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