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Philco 90 dial lamp flicker? - Printable Version

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Philco 90 dial lamp flicker? - sdradioman - 06-09-2015

Has anyone ever had the dial lamp on their model 90 cathedral start to alternate between bright and dim after about a half hour of operation? I bought this 90 that had just been restored electronically back in January. The gentleman I bought in from spent $375 getting it up and running by a member of the Colorado Antique Radio Club. When I bought it the seller turned it on and it played beautifully. It then took a 10 hour ride from Colorado back to South Dakota. I got it home and it plays great, but I noticed that after about a half hour of operation the dial lamp wasn't as bright as it normally is. It seemed to get dim and then go back to being bright. It didn't seem to change with volume or changing the station. I really hope that the power transformer isn't going bad. Could it be a tube starting to short out? Any help would be greatly appreciated because I spent quite a bit of money on it.

RE: Philco 90 dial lamp flicker? - morzh - 06-09-2015

Do you hear any correlation in sound when this happens (volume etc). If not could be as simple as the dirty socket.

RE: Philco 90 dial lamp flicker? - sdradioman - 06-11-2015

No, no change when volume was turned up or down and no change when changing stations. It would just go dim and then bright, then back to dim and then bright, over and over again.

RE: Philco 90 dial lamp flicker? - Radioroslyn - 06-11-2015

I'd make sure that the base of the bulb and the socket are good and clean. Check to see that the connections at the base of the socket are not shorting(to each other or to the chassis).       Does the volume go up or down by it's self?? Even a little bit?? Don't know which version you have (single ended or P/P output) If you have the P/P output stage watch the filament on those two tube to make sure both are staying lit. If one is intermittent that can cause your problem.

GL
Terry

RE: Philco 90 dial lamp flicker? - mikethedruid - 06-12-2015

First thing I would check is the socket of the bulb itself. If the rubber is dead in it, it may not be making a good contact once it warms up and things expand slightly from the heat. Cold, the bulb will make a solid contact, but as things warm up, the metal and other things expands, and the bulb become slightly loose. Try tapping the light socket with the radio on and warm, and see if that causes the problem to appear. In any case, if you have not rebuilt the socket, I would do so.

RE: Philco 90 dial lamp flicker? - DeckApe - 06-12-2015

Simple thought: a failing filament in an incandescent bulb can also go brighter or dimmer, as the weak point gets thinner (at least, if I recall what my electronics prof told me--I wish I'd paid more attention in class!). Gamble a new bulb while you're at it.

RE: Philco 90 dial lamp flicker? - Radioroslyn - 06-12-2015

Don't think the 90 uses a socket with rubber I think it has fiber washers. The later sets do have the disintegration rubber like the 37-116.

Terry