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Hi All, I decided to tackle one of my favorite radios next. The Philco ‘Hippo’ I purchased in Seattle 10 years ago. I found it at a big antique warehouse near the waterfront and after taking it back to the ’40’s era hotel room we were staying at, I turned it on and listened to an episode of ‘The Shadow’. It was like a surreal Twilight Zone episode where the old radio only plays old tunes and shows!
Sitting on the shelf for 10 years and being dragged to Montreal from Vancouver didn’t help and it had lost it’s voice. I found that I had all the caps in stock so I carefully cleaned all the controls and chassis and changed all the caps and the radio works very well now BUT the sound still trails off after 10-15 mins like it did 10 years ago. Let it cool down and it’s good to go for another 15 mins. Is this a common tube radio issue? I haven’t encountered this scenario yet.Gary K.
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Gary;
It might be possible that a resistor has a short in it and when it heats up it breaks contact.
I do not know for sure, but it is worth a try to at least inspect the resistors.
Just a guess .
Dan in calgaryDid you check your tubes? Also after it warms up and sound starts to drift away , did you shut down the radio and see if your caps or any other part has got hot? Also did you do a voltage test before and after the radio starts to drift?
Hi Dan, Sterling
Checking the resistors and swapping out tubes was next on the list as it seems to be a heat related failure. Have to find a better schematic first. Sterling ,Yes I tested all the tubes and they test perfect on my tester, however I’ve read that this kind of problem can be a failed tube that tests perfect and doesn’t appear until they get hot. So, I’ll start with the tubes first one by one since I’m sure I have some of the same tubes in my other Philcos, but I haven’t looked yet.
Gary K.Forgot to mention but never done this but might work. Take and record readings of the tubes when they are cold and compare to readings from the tubes when radio starts to operate wrong. Just a thought.
I have found 4 out of 6 replacement tubes from my other Philcos radios and replaced them one by one and let it warm up. each time the sound degraded over time as before. The only tubes i didn’t have was the 7C7 and the 50B5. I have a 50A5 and a 50C5 and both have a different pin arrangement and can’t be substituted The 7C6,7B7 ,7A8, 35Z5 all check out as o.k. It’s looking more and more like resistors although there aren’t that many. My printer stopped working so I can’t download schematic diagrams. Until I get that issue resolved, I will put this radio on the side for now.
Gary K.
O.k. Had another look at the Hippo and noticed it would cut out and react badly to anything touching the chassis. I flipped the chassis over and while it was working I gently probed around and as I touched one of the coils the radio cut out. I had nudged it slightly when I replaced a nearby cap. I clipped it back in place and the radio works perfectly. One more done!
Gary in Montreal
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