Volume getting lower? - Printable Version
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Volume getting lower? - ODPILOT - 07-25-2014
7/25/14 I have restored a 53-1750 radio phonograph console. All new caps & resistors - the thing WAS working great for a couple of months, but recently has a noticeable decrease in maximum volume. No buzz, no nothing else, just won't go as loud all of sudden. This applies to both the radio and the phonograph volume. Does that sound like anything in particular? Tubes test good. I tried jiggling the phonograph/radio switch, the volume switch - any ideas?? Tubes in this set include:
50Y7GT, 35L6GT, 7c6, 7B7, 7A8. Thanks.
RE: Volume getting lower? - morzh - 07-25-2014
What about your volume pot?
RE: Volume getting lower? - ODPILOT - 07-26-2014
You know, I don't think it's the pot. It doesn't seem to produce any static noises when I turn it. But, I know what your talking about cause that sort of problem pops up all the time with my guitar amps or pots on an older guitar. I did try turning and jiggling the volume pot - doesn't seem to matter. I wonder if it might be a tube even though they test good. I'm actually going to be restoring another 53-1750 (real nice blonde color model) and it has same set of tubes which also test well - I'm gonna swap some tubes out and see what happens. Thanks.
RE: Volume getting lower? - morzh - 07-26-2014
Pilot
Yes it could be a tube even though it tests good, let alone the fact some testers do not even test mutual conductance, but even if they do you might have a problem, just like the one I have fixed a week ago, looks like grid leakage.
If it applies to phono and RF, I would start changing from Phono preamp tube and proceed down to the audio driver tube by tube. I do not have 53-1750 but if 53-1754 is any similar, there are 4 tubes to try.
RE: Volume getting lower? - jerryhawthorne - 07-26-2014
Wtih the radio and phono going down, work on the audio section as indicated by Morzh. Swap tubes first. Clean sockets second and check voltages on the audio tubes.
Good luck, Jerry
RE: Volume getting lower? - codefox1 - 07-26-2014
Confirm with a kid, otherwise ask the doc.
RE: Volume getting lower? - ODPILOT - 07-26-2014
7/26/14 - Both Jerry and Morzh - you guys got it !! I was a tube. After taking a few minutes and swapping out some of the tubes with other known good ones, it turns out it was the 50Y7GT tube. When I rechecked the tube in the tube tester it tested BAD on a second setting (I guess a second filament) that I had overlooked to check. When I popped in the extra one I had - it went back to full volume. Thanks guys !
RE: Volume getting lower? - jerryhawthorne - 07-26-2014
ODpilot ,we are glad we could offer some ideas. Mortz is a lot smarter than me.
Your now off and running. What will the next radio be? None of us stop at one (or a lot more). And yes, rectifiers typically will require the testing of each diode section. Meaning changing your tester to try both.
Best, Jerry
RE: Volume getting lower? - Arran - 07-27-2014
A 50Y7 is a full wave or voltage doubler style rectifier, so if one section is bad, or gets flaky in emission the B+ voltage will drop. There is only one filament but two cathodes.
Regards
Arran
RE: Volume getting lower? - ODPILOT - 07-27-2014
TO: JERRYHAWTHORNE - it sure does seem to be addicting to fix these things up. As a kid, we had a blonde 53-1750 (may actually be B-1750). I believe they made this model as only in the Mahogany stain in 1953, but in 1954, then introduced the Blonde color and called it B-1750 (B for Blonde?). The one I fixed up is the Mahogany but I just purchased the Blonde one from 1954 - that's the color we actually had as a kid and so I'm going to bring it back to life. That blonde model seems to be extremely rare. After that, I don't know - if I bring any more I may have to move to a bigger house. Cheers.
Mike
RE: Volume getting lower? - Arran - 07-27-2014
Not exactly, the B has nothing to do with the cabinet finish, but it has everything to do with it being a 1954 model. Beginning in 1954 Philco abandoned it's practice of using the last two numbers of the year as a prefix for the model number, though I have no idea why. So U.S built Philcos built between 1937 and 1953 began with 37-116, 38-116, 39-116, 40-180, 42-327 etc. etc., but for 1954 they switched to using letters to denote the model year, which was something General Electric did in the 1930s and 40s.
For some strange reason they started with the letter "B" rather then an "A", I guess maybe it was to avoid confusion with car radio models where the "A" stood for auto. So if you have a Philco with a B-XXXX it's a 1954 model, if it's a C-XXXX it's a 1955 model. I don't really know what they planned to do when they ran out of letters, maybe double them up?
Regards
Arran
RE: Volume getting lower? - ODPILOT - 07-29-2014
Aran - I didn't know that. Interesting little piece of Philco trivia. Usually when that kind of stuff happens (i.e. changing to B for 1954 instead of using the prefix numbers), there's usually some over paid, BORED executive at a company that brainstormed this change while they were twiddling their fingers at their desk. !! Thanks.
Mike