Hello again.... I have fixed my IF transformer and the radio is working fair. The sensitivity is low, but my voltages are checking ok. I have recapped all caps, and changed some resistors that were out of tolerance.

The audio sounds ok.... some mushiness to it, not sharp and clear as I would expect, but plenty loud enough.

Anyhow, I have a problem. The IF has been aligned correctly, and I know the oscillator is functioning properly. Both were tested and aligned using a HP service monitor, and I know it's correct.

I have a local station in town on 1490 that is strong. They are in the correct dial position, but also show up quite strong around 580 range, and sometimes in a couple of other spots, though not as strong.

I can't find out how to adjust out the image like a wave trap. I have no idea what could be causing this. Any ideas on what this strange behavior might be?

Does the tuning cap have a wire that goes from one gang top to the other? If so make sure that it is removed. This was a "gimmick" wire that is not supposed to be electrically connected, The rubber insulation usually broke off this shorting the sections of the tuning cap causing this situation of images from top of dial show up at bottom of the dial.

There is no wave-trap on this radio. With no RF amplifier stage or any other better method of pre-selection you are bound to get images on strong local stations. I have the same issue with a strong local station where I live.

On the audio issue, have you checked the speaker to make sure the cone is freely moving? Make sure the voice coil is not rubbing when the cone moves in and out and also check that the outer edge of the cone is secured to the frame. Sometimes the glue that adheres the cone to the frame degrades and the cone comes loose.

Hi

Although Philco 41-608 has 2 IF stages and push pull output it does not have a RF stage. Only a triode is used for the 1st Det. This radio depends on antenna tuning to prevent a strong station at 1490 from being heard at 580. With an IF frequency of 455 we would expect a strong signal to come through at 580. 1490-580 = 910 divided by 2 = 455

If the antenna tuner is operating properly and it comes through need a tuned RF stage to prevent hearing the signal at 580.

http://www.nostalgiaair.org/PagesByMode ... 013433.pdf

Thank you all. I will be examining later today and will report back. I made the newbie mistake of not connecting the antenna in the frame. I was using a regular external single wire. That can't happen with this radio and expect it to perform correctly from what I understand. I haven't restored any philcos, just atwaters. But I'm getting there. Will definitely look at the speaker.

Joe

well, happy to report that connecting the internal antenna has fixed the image frequency problem.... Now.... I have to find the audio problem. With the volume all the way up, and a bit before, the audio kind of makes a relatively high pitched burp, burp, burp, burp, burp, burp sound. If you sing the word burp about every second at a relatively high pitch, that's what you'll hear, along with the audio.

I don't know how else to describe it. Kind of like a bird chirping, but not that high pitched, a little bassier.

I'll look at the speaker next.

joe

This radio will sound "mushy" if someone had accidentally killed the negative bias by grounding the filter caps.

Check that there's 10 to 20 volts negative at the minus side of the filter caps.

Ancient..... THANKS!

I also discovered I had a .01 instead of .0015 cap across the push pull AF plates.

The 2nd filter cap (16 ufd) was indeed just hooked to ground. It had zero negative voltage obviously. Anyhow, I fixed that and connected it correctly and the audio is now FINE! Thanks to all who helped!

Gonna realign now since so many things have changed.

What would cause the bottom of the tone control (Bass) to be really distorted sounding??? The rest of radio works fine. It tests about 1-6Mohms when turning it connected to ohm meter.

Hmm, hard to say, maybe if the 0.004 uF capacitor from plate to tone control was leaky.

Also bass takes a LOT more power than the higher tones to reproduce, if your output tubes are weak they're not going to be able to reproduce bass. Also a weak speaker surround can distort the bass.

Update for everyone.... someone years ago had wired the center tap of the volume control into the bias resistor junction for the AF tubes via capacitor that should normally go the screen of the 2nd detector/1st audio tube, thus giving me NO screen control of the 2nd Detector. This caused oscillation with volume all the way up, and horrible distortion on the bass/tone control when maxed. The capacitor blocked the negative voltage normally on the bias of the AF circuitry, but it of course provided an AC path for signal, totally changing everything about the radio.

This explains all of the weird distortion and scratchiness of the pots. It had been that way for a very long time, and I just stumbled upon it when tracing out the circuit to the schematic. The old Philco now sounds absolutely incredible, and it's been a joy to restore it. Thanks to all for the help.

Don't think that is a screen I mentioned.... not sure what exactly that does, but it has to be some kind of controlling mechanism on the 7c6 tube, and it wasn't connected correctly.

That would be the control grid you're talking about.

So, then it would be appropriate to say that the 7C6 control grid became capacitatively coupled to the input grid of the push pull amps for some unknown reason.... that made all kinds of bad things happen