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Old 12-17-2016, 10:31 PM
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Radiotronman Radiotronman is offline
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Philco 40-155 audio output

Does anyone know the exact replacement for an audio output transformer in a philco 40-155. I can barely get any sound and when I do resistance checks on this transformer I only get 160oms in one section. I get nothing in the other section.
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Old 12-18-2016, 01:17 PM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by Radiotronman View Post
Does anyone know the exact replacement for an audio output transformer in a philco 40-155. I can barely get any sound and when I do resistance checks on this transformer I only get 160oms in one section. I get nothing in the other section.
The output transformer has to be good for Philco's phamous phunky phase inverter to work properly.
I don't know why they bothered to make it as a form of push-pull, as according to the service information, it's only good for two watts output.
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Old 12-20-2016, 08:45 PM
Captainclock Captainclock is offline
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Quote:
Originally Posted by dieseljeep View Post
The output transformer has to be good for Philco's phamous phunky phase inverter to work properly.
I don't know why they bothered to make it as a form of push-pull, as according to the service information, it's only good for two watts output.
Although for 1940 standards 2 watts is pretty good, considering some of the other radios from that time period barely put out 1 watt of audio output in 1940...
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Old 12-21-2016, 08:36 AM
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Scott,

You can use a Hammond 125A that is rated at 3W with taps to match the plate-to-plate impedance to the speaker. The tube data shows 12,000 ohms plate-to-plate impedance.

I was trying to come up with a synonym of inverter to make the entire name for this circuit begin with ph. How about Philco's phamous phunky phase phlipper?

For an even stranger push-pull output check out the schematic for the General Television 9B6. I had one of these at one time and thought this was the most off the wall output circuit. One 50L6 driven through the grid, common cathode bias resistor between the two 50L6s, second 50L6 has its grid grounded.

General Television 9B6
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Old 12-21-2016, 10:45 AM
dieseljeep dieseljeep is offline
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Although for 1940 standards 2 watts is pretty good, considering some of the other radios from that time period barely put out 1 watt of audio output in 1940...
Many of the sets built back then used a single output tube, but using higher plate and screen voltage. This pertains to the lower cost transformer powered table models and consoles.
The one watters were the AC/DC types, table radios, etc.
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Old 12-23-2016, 08:59 AM
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Very interesting. Thanks Sean, I will order one of those. A fiend of mine recapped this radio and couldn't figure out why it didn't work. So he brought it over to me to troubleshoot. I had to replace most of that rubber wire that is so shrunken in these early forties philco sets.
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Old 12-29-2016, 09:18 PM
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Radiotronman Radiotronman is offline
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My audio output transformer came in and I installed it. I now have some sound, but I only have one weak station that you hear all across the dial. It's like the tuner has no effect on this set at all. Any ideas on what is keeping this set from tuning in stations across the dial?
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Old 12-29-2016, 10:17 PM
old_coot88 old_coot88 is offline
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The local oscillator (LO) isn't running. First thing to do is DeOxit the pushbutton switches and band switch if you haven't already.
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Old 01-12-2017, 01:33 PM
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I cleaned the bandswitch and bandswitch, with no improvement. This is a pretty simple set, what could be wrong?
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Old 01-12-2017, 03:47 PM
old_coot88 old_coot88 is offline
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Have you DeOxit'ed the socket of the osc./mixer tube (7J7)? With loctal tubes, the pin-to-lug connections in the socket tend to get flaky over time. Probly a good idea to do it to all the loctal tube sockets. Then wiggle the tubes in their sockets to fully seat all the connections.
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Old 01-16-2017, 01:59 PM
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Scott,

I usually take some sandpaper to the pins on those loktal tubes. Something like 400-600 grit should work. If that doesn't work, start checking continuity on the oscillator coil. Does it not work on any of the bands? Does it work with the push buttons?
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Old 01-16-2017, 09:21 PM
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Radiotronman Radiotronman is offline
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Sean,

I hear one faint station, and it's the same no matter what band I'm on. When you press a push button, that one station disappears. I'll clean those sockets like you suggested.
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Old 01-18-2017, 08:17 PM
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You might check if one of the pushbuttons is for "DIAL" tuning, and the rest for presets. The set has 8 pushbuttons, count the preset tuners in the back...
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