Well I spent the last 4 days in the hospital with a collapsed lung. Fine now and need help with the FM alignment on my Philco 46-480. Please!!! The AM align. went really smooth. My instructions call for a "DC Vacuum Tube Voltmeter" to be connected across the 5mfd cap C43. I don't have this meter. Is this meter just a voltmeter that has a specific volts per ohm capability? If so, why can't I use a modern DVM? Also, am I just monitoring the voltage across C43 during alignment? Thanks all!

Actually, a VTVM is the "old school" equivalent of a DVM. As the saying goes: "use it if ya got it". Just remember that a digital meter is not as easy to see subtle changes in voltage as a nice size analog meter movement. But it will work just fine.

:Actually, a VTVM is the "old school" equivalent of a DVM. As the saying goes: "use it if ya got it". Just remember that a digital meter is not as easy to see subtle changes in voltage as a nice size analog meter movement. But it will work just fine.
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:Thanks Anthony! I used my meter and it seems to work fine. I am seeing voltage changes across C43 during alignment but when I perform step 3 of the alignment procedure C32 seems very unstable and FM reception is improved slightly just by touching it. I'm baffled. To open the can that houses C32 I need to unsolder all wires from the circuitry. Even after getting a somewhat stable reading I still have no FM reception at all. I get lousy FM reception in my area but other radios in the shop pickup FM just fine. Guess I'll remove the can and check C32 trimmer and then go from there.

If you have no FM reception at all, you probably shouldn't mess with the fine tuning adjustments for the FM circuit at this time. They are more critical than AM adjustments. What model is this radio? Does it have slug adjustments or capacitor adjustments? If it has slug adjustments, most likely it has some sort of fixed silver mica capacitances. These oxidize and either open up or short out depending on the radio. Verify that the oscillator is working, though I'm not sure what voltage you should get at the grid of the FM oscillator since I've never gone that far with an FM radio. Also verify that all tubes are fine in the FM circuitry, that all coils test well regarding continuity (and no shorts between primaries and secondaries or a short across a coil due to a shorted capacitor), and make sure that all voltages test normal (no drifted resistors, opens, or shorts). If you cannot find any trouble in these categories, you might try operating the radio near another FM radio to see if you can hear the oscillator working. I don't know if this works like AM radios or not. If the IF is 10.7 MC, then listen to the test radio for something about 10.7 MC below the station being tuned in on the Philco. If the IF is something else, look for a frequency of the station minus the IF. If the oscillator seems to work, try injecting a signal into the IF circuitry at the IF (tune your signal generator to the IF). Fluctuate the frequency up and down slightly, since the discriminator only responds to frequency changes, and might not do much if you send it a single frequency. If you can get a signal through well, check out the front end. If not, check out the IF circuitry. You might need to dig out some of the IF transformers' capacitors and replace with new ones (preferrably mica, since mica is most stable).

The IF transformers in an FM set should be adjusted according to manufacturer instructions. The primary stage(s) can usually be tuned to the IF, but the discriminator typically has to be staggered a bit so that it passes a comparatively wide bandwidth. The discriminator must respond to frequency changes. The louder the intelligence, the more the incoming frequency shifts up and down. If the bandwidth of the IF circuitry is too narrow, it won't respond to wide frequency changes, and so loud passages will distort.

T?

:If you have no FM reception at all, you probably shouldn't mess with the fine tuning adjustments for the FM circuit at this time. They are more critical than AM adjustments. What model is this radio? Does it have slug adjustments or capacitor adjustments? If it has slug adjustments, most likely it has some sort of fixed silver mica capacitances. These oxidize and either open up or short out depending on the radio. Verify that the oscillator is working, though I'm not sure what voltage you should get at the grid of the FM oscillator since I've never gone that far with an FM radio. Also verify that all tubes are fine in the FM circuitry, that all coils test well regarding continuity (and no shorts between primaries and secondaries or a short across a coil due to a shorted capacitor), and make sure that all voltages test normal (no drifted resistors, opens, or shorts). If you cannot find any trouble in these categories, you might try operating the radio near another FM radio to see if you can hear the oscillator working. I don't know if this works like AM radios or not. If the IF is 10.7 MC, then listen to the test radio for something about 10.7 MC below the station being tuned in on the Philco. If the IF is something else, look for a frequency of the station minus the IF. If the oscillator seems to work, try injecting a signal into the IF circuitry at the IF (tune your signal generator to the IF). Fluctuate the frequency up and down slightly, since the discriminator only responds to frequency changes, and might not do much if you send it a single frequency. If you can get a signal through well, check out the front end. If not, check out the IF circuitry. You might need to dig out some of the IF transformers' capacitors and replace with new ones (preferrably mica, since mica is most stable).
:
:The IF transformers in an FM set should be adjusted according to manufacturer instructions. The primary stage(s) can usually be tuned to the IF, but the discriminator typically has to be staggered a bit so that it passes a comparatively wide bandwidth. The discriminator must respond to frequency changes. The louder the intelligence, the more the incoming frequency shifts up and down. If the bandwidth of the IF circuitry is too narrow, it won't respond to wide frequency changes, and so loud passages will distort.
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:T?
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:Thanks Thomas, The radio is a Philco 46-480. If I'm correct this radio has capacitor and slug adjustments. I know what a capacitor adjustment is and... is a slug a small white kinda square 1/8" thick looking thing with an adjustment screw in the center? Your reply will be of great help. Now I'll go check all those things. Thanks!!!

Nice radio. THis radio DOES NOT have slug tuned IF transformers. A slug, as far as radio is concerned, is a small cylindrical shaped piece of powdered iron. By various methods the powdered iron slug is adjusted so that it moves into or out of its respective coil, which changes the inductance of the respective coil. Your radio uses capacitive tuned IF transformers. The white squares you see are porcelain insulators. The adjustable trimmer capacitors are mounted to the porcelain. The capacitors consist of sprung leaves of metal insulated with mica. A screw, which is insulated from all metal leaves, is used to compress the leaves together to increase capacitance or to allow them to spread apart for decreased capacitance. This style of IF transformer rarely fails.

For starters check all resistors for drifting (disconnect one lead of resistor in question when necessary). Check voltages. Check coils for proper continuity. Check for shorts across individual coils (windings). Check for shorts between coils (from one coil to another). Check tubes. Check oscillator circuit. Check band switch. Try injecting the intermediate frequency into the intermediate frequency circuit as I mentioned before. Be sure to hook an antenna to the FM front end. If you absolutely cannot find faults, inject IF frequency into IF circuitry. Adjust IF transformers for maximum tone in speaker. Then follow instructions given by Philco (you can find them on this site under Resources). A sweep generator is preferred, though you can probably hear the tone of a regular signal generator (I usually do).

T.

:Nice radio. THis radio DOES NOT have slug tuned IF transformers. A slug, as far as radio is concerned, is a small cylindrical shaped piece of powdered iron. By various methods the powdered iron slug is adjusted so that it moves into or out of its respective coil, which changes the inductance of the respective coil. Your radio uses capacitive tuned IF transformers. The white squares you see are porcelain insulators. The adjustable trimmer capacitors are mounted to the porcelain. The capacitors consist of sprung leaves of metal insulated with mica. A screw, which is insulated from all metal leaves, is used to compress the leaves together to increase capacitance or to allow them to spread apart for decreased capacitance. This style of IF transformer rarely fails.
:
:For starters check all resistors for drifting (disconnect one lead of resistor in question when necessary). Check voltages. Check coils for proper continuity. Check for shorts across individual coils (windings). Check for shorts between coils (from one coil to another). Check tubes. Check oscillator circuit. Check band switch. Try injecting the intermediate frequency into the intermediate frequency circuit as I mentioned before. Be sure to hook an antenna to the FM front end. If you absolutely cannot find faults, inject IF frequency into IF circuitry. Adjust IF transformers for maximum tone in speaker. Then follow instructions given by Philco (you can find them on this site under Resources). A sweep generator is preferred, though you can probably hear the tone of a regular signal generator (I usually do).
:
:T.
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:Thanks Thomas! I've printed all this stuff out to keep for future reference. The problem turned out to be Loctal problems. I cleaned all the sockets and the tube pins when I rebuilt this thing. I had to go back and clean again and this time actually tweek each tube pin for a snugger fit in the socket.
Everything works good now. When I got this radio it had serious problems. I had to completely remove the band switch assembly because there were a few resistors and one cap underneath of everything that were fried. If you're familiar with this radio then you know that removing the band switch isn't an easy task. Lots of digital pics and many notes prior to disassembly. Thanks again for all the help.