Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Self Osc in output on 41-296
#16

Raleigh, yes. I wasn't sure if they did that just for alignment, or possible output to another speaker with the main speaker output out of circuit.

Interesting on the the other comments. Since I don't have the cabinet here, I am going to take this and install and recheck the hf osc. I hope I can reach the two on the left (from the back) front if I need to. I suspect the BC will change much, if at all. It tracks perfectly the way I have it now.

Terry, I bet you and BAD are right. I tuned my Icom 746 up and down the same range the SW bands are on the Philco and hear one carrier or something every few kcs. Now if I can just get the hf osc on the 9 to 12mcs band to align I'd be done. Something is not right with that. I am unscrewing the trimmer way out to get what appears to be the fundimental on my SG, but hear two signals about a kc apart that about equal in strength. Only thing I can see different in the osc to speak of between SW1 and SW2 is an 84pf mica which I replaced, in series with the tuning condensor. I got a new 82pf (checked) which should not have made that much difference, but it may have changed since I put it in there. I've got some 2pf ceramics I could parallel with it, but not sure I should put a ceramic anywhere in the osc. section... Could try it I guess.
#17

A KC apart, or a MC apart?

If it's a MC apart, this is normal. Actually, closer to 900 KC, depending upon your IF frequency. These would be images. When doing the alignment on HF, you will likely have this. It can be tricky to get the right one. When doing the alignment, use a strong signal at first, but once you think you have the right signal, back your generator off until you barely hear the signal, then check to see if the other one is still there, it should be very weak or gone. Verify proper tracking by backing your generator off 1 MC at a time and check for the signal at that frequency. It should follow very closely.
#18

Sorry, I meant 1 mc apart!

Is the LO on this band going to be heard 455 kcs below, or above the "tuned" freq.? The signal I hear close to 10 Mhz DOES have an LO below, but not above, if so I think I have the fundamental spotted and zeroed in on 10 Mhz now. The image above at about 900 kcs is a lot stronger than I would expect however. Nearly as strong as the fundamental. I can actually hear WWV in both spots too. I don't expect to get it within a needles width accurate. Actually 50 to 200 kcs would be fine with me. Maybe I have it pegged now since I was looking for the upper LO instead of looking below (10000 - 455 = 9545).

Thanks,
Brian
#19

If you're hearing WWV at both spots, then your RF and Antenna tuning is off. I've never been certain whether these sets tune with a high or low LO frequency. I've always assumed high, since that's the norm for BC radios, but not everyone does things the same way. Ron or Steve may know better than I.
#20

Brian, Your receiver has only a single tuned circuit before the mixer, so I would not expect great image rejection on the highest freq band. Even when properly aligned you will still hear the image, although it should be a bit weaker.

I am not sure if it is high side or low side injection, but you might just try to set the LO to select the mixing product that allows the LO trimmer to be closest to the center of its adjustment range.

Mike, WA2YGA
#21

Maybe I have the answer. You mentioned that you don't have the cabinet. Some of those sets have a loop ant for the SW bands. If that isn't connected then there isn't a tuned circuit across the incoming signal which will allow all kind of noises to come in. Just a thought.
Terry
#22

Thanks guys. Good thoughts, and I do suspect a lot of this wierd stuff is not having the loop hooked up. I plan to take it down to my friends place later this week and re-install it in the cabinet. We will see what happens then. Other than that little oddity, it is working great. I was very surprised how well the audio sounds with the 12" speaker just sitting on the floor. Can't wait to hear it in the cabinet. This was my first Philco to work on, and have learned some and really enjoyed it.

Here is gallery of some of the vintage ham rigs and one "farm radio" I've done over the last few years:

http://w5ami.net/cpg1419/index.php?cat=5

Thanks so much for all the help!

Brian / w5ami
#23

Oh yes, and thanks to the admin for providing a great resource here. The folks behind the scenes, that set these up for us to use freely sometimes get forgotten!

Brian / w5ami
#24

I had a lot of weird stuff going on when I was working on my 40-150 with just a long wire for a working antenna. When I aligned it with the loop and reinstalled it in the cabinet all or almost all of it went away. That might corroborate the comments from 7estatdef.

John Honeycutt
#25

Thanks John. Yes, I am anxious to get it in the cabinet in the next few days, hooked to the loop antenna and see what happens. I just hate trying to get to those trimmers. Actually, it seems to be doing pretty good now. The "birdies"/squeals have all but gone away now and I don't really know why. I may have got lucky and moved a wire or something that was causing it. I am pleasantly surprised how well the audio sounds now that I found the open winding on the old audio xfmr and got this new one. One tube working in a P-P circuit just doesn't cut the mustard!

Brian
#26

When I align my 1941 table sets I put the chassis and the cabinet back to back and connect the wires to the loop with the loop still mounted in the cabinet. I can get to the trimmers that way, so I don't need to reach inside the cabinet. When I reinstall the chassis, the dial alignment does change a very little.

That technique might be harder with a console, but you can figure out a way. I did it with my 41-280 by putting a tall stool behind the console. I put the chassis on that stool, right behind the console, so I could connect the wires from the loop. The dial alignment ended up very close.

I don't know if in your set the dial glass comes out with the cabinet, but I think it probably does. On those sets with the glass mounted on the cabinet, I put the chassis in the cabinet and slide the pointer to the low frequency mark with the tuning condenser closed. Then I use the tuner knob to set the pointer at the reference frequencies and mark the position of the pointer with a sharpie on the back of plate the pointer slides on. That way I can put the pointer pretty close to the correct frequencies with the chassis out before I turn the trimmers.

By the way, I never had any real difficulty with weird noises and images with my 1941 sets on a long wire test antenna, but the 40-150 has a more complicated loop that might explain it. I was at my wits end and finally decided to give up and live with the noises and images, but when I put the chassis back in the cabinet with the loop connected properly, they all went away. They were all caused by my long wire test antenna.

John Honeycutt




Users browsing this thread: 2 Guest(s)