[jtiner]

I restored a Philco 41-255 some time back and all appeared to work well, though I recently noticed the upper SW band (9-12 MHz) seemed to receive far fewer stations than my other radios, and apparently at the wrong place on the dial. Performance on the BC and 2-7 MHz band is as expected. I revisited my alignment, IF and oscillators, and all was as it should be. The alignment instructions for the 9-12 MHz band specify adjusting  the oscillator compensator to the fundamental frequency, and that seems to work as described - starting from the closed position on the trimmer then backing out CCW for the first peak. When I check the alignment with my generator, dial tracking is very poor on the mid/low end of the dial, and received signals are weak, with a much stronger image received about 1 MHz higher on the dial. I'm assuming it's 910 KHz higher.
I used the spectrum analyzer loosely coupled near the chassis to watch the LO frequency vs dial frequency, and for the BC and 2-7 MHz bands, the LO is 455 above the tuned frequency and tracks well. But on the problematic 9-12 MHz band, the LO is 455 below the tuned frequency. So now, if a known strong station is at 9.3 MHz, I can barely know it's there at 9.3 on the dial, but receive it normally at 10.2 MHz.
I can't find any way to make the upper SW band LO run 455 above dial frequency, which is counter to alignment info but would match the other two bands. If I open the trimmer to get the LO at 455 KHz on the high side at 12 MHz, it tracks so incredibly poorly that by 11 MHz on the dial, the LO itself is at 11 MHz, then it's soon farther and farther below the tuned frequency. I'm attaching the Philco schematic, as well as the alignment instructions for the similar model 41-280, which is what Philco specifies as instructions for the 41-255.
I've triple checked my original work. That included replacing the oddly packaged dual capacitor C21/C21A with two discrete 360 pF silver mica capacitors in the osc./mixer circuit. The other discrete silver mica capacitors in that circuit appear to be at the correct value. I've also measured continuity of the various band switch connections related to the upper SW band, including coils, etc., and soldered every riveted chassis connection, including the chassis connections of the oscillator trimmers. And of course I've cleaned the oscillator tube/socket pins. The oscillator trimmer is one half of a dual trimmer, and it measures 0-90 pF, though no value is given in the parts list.
I don't have enough hair to pull out, but that's where I'm at. I'm hoping someone can point me in the right direction on this one.

EDIT: original 1st post text replaced with this more accurate description of the problem

[Radioroslyn]

I would use a frequency counter or digital sw receiver coupled to the osc to read its frequency. This way you'll know whether you are on the high or low side of the IF.

[jtiner]

I'm using a counter with my generator for accuracy in setting test frequencies, and for monitoring what's going on in general I use the spectrum analyzer with a loop so I can see the generator's output in the air, as well as the LO. It appears that the radio is designed for LO above on 2.3-7 MHz and LO below on 9-12 MHz. I should mention that the LO is surprisingly strong - I don't need the analyzer lead to be near the radio to see it.
For a sanity check, I made sure the generator's output wasn't spurious or intentionally harmonic (well, it is by design above 32 MHz...). I also checked around the dial, and I can hear the same broadcasts just about 1 MHz apart (I assume 910 KHz). The higher frequency is always stronger, whereas the alignment instructions suggest it should be significantly weaker.
When I first restored the radio, I soldered the mechanical chassis connections for the trimmer assemblies because they appeared unstable (electrically) when performing alignments. Tonight, I went ahead and soldered the mechanical chassis connections for the terminal strips that use the chassis connected lug. If there are any critical rivets that I may be missing, let me know; I didn't see anything else that might require soldering.
One other possibly related problem is that there's no peak on the "aerial padder" designated "2", although I am extending the cabinet loop with 3 alligator clips to the antenna terminals.

[radiorich]

Hello jtiner ,
yes, that smart thinking

"Tonight, I went ahead and soldered the mechanical chassis connections for the terminal strips that use the chassis connected lug. "

I have a wards airline that I need to revist and clean the volume control also do what you did the connections on the chassis were made by rivests and I know there some high resistance from poor connection.

Keep up the good work it sounds like the set is coming along .
Sincerely Richard

[Radioroslyn]

What I can tell you from experience is that most of the time the local oscillator runs above the incoming signal not below. I would algin it accordingly. 
Use the counter to set the 12.455mc (osc) for the dial (12mc) reading. Keep the generator turned way down so there is much avc action and peak the ant trimmer. On the band 2 there is just the high end of the band osc set no ant trimmer. Same for the bcb but there is a low and high set for the osc so you can get the tracking on target, well close. There is no low end set for the sw band so wherever they fall is it. Unless you want to bend the plates on the tuning cap but that effects all bands

I have a 41-300 which uses a similar front end/IF. Works fine w/the built-in loops but try to hook up an external antenna oh my! It's got all kinds of images. I don't one of the 3 pin external antenna adapters that may help. Somewhere there is a diagram of it with the part values.

GL

[jtiner]

I built one of the external antenna adapters and have been using that off and on in my testing. To rule out possible harmonics or other oddities in my generator, I'm finding broadcasts on my Zenith TO, say at 11.5 MHZ, then moving the Philco's oscillator adjustment to find the strongest image of that station at 11.5 on the dial. That does indeed place the LO above the tuning frequency, which is counter to the results following the alignment instructions. But that does match how the "police" band is set. However, what I'm finding is that the LO is tracking very badly, so the lower end of the band is very far off. The BC and "police" bands track very well. I'm taking a break for a while because I've been at it too long today. Thanks for sharing your experiences. That's helpful information.

[jtiner]

Update: I've updated my initial post with a more accurate description of the problem.

[jtiner]

I've been picking away at this without making any headway. I've checked the continuity of each section of the antenna and oscillator coils, and tested connectivity to and through the band selector, and I've checked capacitor values. At this point I'd love to hear from someone who has a 41-255 operating correctly on the upper SW band. To help with diagnosing the problem, I marked up the antenna and oscillator sections of the schematic to show the band switch in the upper SW position. As far as I can tell, there's no antenna tracking when that band is selected - only the LO section of the variable capacitor seems to be in circuit and the antenna circuit is fixed. And I've continued testing the idea that the LO is supposed to be on the high side of carrier/dial frequency, and it just doesn't seem possible. The LO starts well below dial frequency with the oscillator compensator closed and at maximum capacitance. slowly backing the trimmer out moves the LO up in frequency in a linear way and easily places it 455 below dial frequency. But the trimmer has to be sloppily wide open for the LO to be 455 above dial frequency, and then it won't move proportionately to dial frequency at all.

[jtiner]

I wanted to update this thread with what I've found trying to solve this problem in case it's helpful to others. First of all, it turns out that I caused most of the problem myself. I experienced this problem with everything assembled in the cabinet as well as on the bench, so I dismissed the idea of the built in loop being involved. It turns out that when the loop was directly attached with its short leads, I still experienced the problem because I also had my external antenna adapter connected. And if I had the adapter disconnected, I had the loop extended on 12" clip leads. That was critical. And not so obvious, because it did not impact the BC and lower SW band in a readily observable way.
So it turns out that the BC and 2.3 MHz bands do have the LO on the high side, and the 9.1 MHz band uses LO on the low side. The LO/dial tracking was not very good on the 9.1 MHz band (only), and that was ultimately resolved by moving C19, 84pF, up and back ~1/2" from its original spot near the group of wires leaving the band switch. The LO/dial tracking improved significantly and LO was always 420-450 KHz below dial frequency across the dial. C19 is only in the oscillator circuit in the upper SW position.
In my original work on the radio, I'd soldered a few of the critical RF riveted chassis connections, like the oscillator compensator assemblies and a couple terminal strip commons, but this time I soldered all of them, and there are a couple I hadn't even considered before, like the one near the antenna coil.
The reality check on this was receiving known off air broadcasts at 9.3, and with the loop extended on 12" clip leads, or with the loop directly attached but with the adapter also attached, 9.3 on the dial had the correct LO frequency but it was barely possible to pick the broadcast out of the noise at 9.3 on the dial, while it could easily be heard at ~10.2. With the loop (only) directly connected, performance was as expected with strong reception at 9.3 and a weak image at ~10.2. And, the adapter was problematic regardless of whether it was set for "local" with no external antenna, or set for "distant" with a 10' wire. Now, the adapter is one that I made from the diagram for the Philco 76-1134, so it's completely possible that it's not built correctly or that it's not correct for the 41-255. My final item to resolve is trying to make sure that the loop antenna resonance is tracking the dial, which I've been able to see with my scope, but I'm certain my scope is affecting resonance so I can't really confirm how well that's tracking. C9, 98pF, is measuring 108pF, so I may replace that.