04-15-2013, 05:45 PM
I'm just about to throw in the towel, so thought I would put this out there for the experts who may have a clue, or direction for me to go. I have entitely recapped, replaced all but about three resistors, and just today replaced the micas in the Osc and RF sections. Only caps I have not replaced or checked yet are the fixed ones inside the 3rd IF xfmr.
I have checked both the antenna and osc coils at least 4 or 5 times, and they have continuity as they should. I have tried at least three XXL's, and the one I have in there now tests well above minimum on a TV-3/C.
I have cleaned and checked the tuning condensor for trash, and bent plates.
I have soldered all riveted ground lugs to the chassis in the area of both the RF and Osc. All wires have been replaced. Bandswitch cleaned and inspected, and all IF xfmrs check good for continuity.
I have not taken any time to align the other bands, but I do hear SW stations on the 9 - 12 mc band, but not sure they are where they are supposed to be. I also hear a lot of what sounds like birdies on the upper band.
I have aligned the IF with my Motorola 1200 @ 455kc per the instructions. I should mention that I get two peaks on the IF with the slug on the 1st xfmr. One nearly all the way in, and one out quite a ways. Not sure what that's about, but using either peak does not seem to affect my problem.
Here is a schematic I posted the other day to the forum on another question I had:
http://philcoradio.com/phorum/attachment.php?aid=1749
The primary problem is this:
While attempting to adjust (with trimmer 16) the HF osc for the BC band at 1500 kcs, I can hear what I think are only images, and only two where the trimmer is nearly fully compressed.
I can not hear anything at 550 kcs, so I am unable to attempt alignment there.
Reason I think the signals I hear are images is that once I align one of them and try to hear stations on the BC band, there is nothing but static. I can however just start turning 17 out and hear BC stations going by, but if I set one dead on with 17, it is extremely wide and no other station can be heard using the tuning condensor, just that one nearly 1000 kcs wide!
Inserting the antenna does have a great effect on reception of static and strength of the BC stations I can tune in using trimmer 17.
I have measured the voltage at the grid of the XXL Osc the best I can without a VTVM, using a scope, and see only about -2 volts. Assuming that's correct, I would think it's not enough negative. What should it be? The plate voltage on the XXL Osc shows 40+ volts, and about 95 on the XXL 1st det.
The real mystery is where I find the LO using a ICOM 746. I can only find one. Setting the tuning condensor at the top of the band, about 1700, the LO is heard at 1292 kcs, and at the bottom, about 550 kcs, the LO is heard at 1244 kcs.
I'm at a loss at this point. Only thing I haven't done is replace tube sockets.
Since I have temporarily removed the push button assy., I can not check it, but my next step might be to re-install it to see if I can get them to work with thier own tuned circuits.
Yes, I have inspected my replacements, caps, resistors, and wire just in case I tied something to the wrong terminal, but I plan to go over it once more since I'm just not getting anywhere with this. I hope my lengthy description covered everything and makes some sense.
Any help will certainly be appreciated and very welcome. I just feel like I've hit a brick wall.
TIA
Brian
I have checked both the antenna and osc coils at least 4 or 5 times, and they have continuity as they should. I have tried at least three XXL's, and the one I have in there now tests well above minimum on a TV-3/C.
I have cleaned and checked the tuning condensor for trash, and bent plates.
I have soldered all riveted ground lugs to the chassis in the area of both the RF and Osc. All wires have been replaced. Bandswitch cleaned and inspected, and all IF xfmrs check good for continuity.
I have not taken any time to align the other bands, but I do hear SW stations on the 9 - 12 mc band, but not sure they are where they are supposed to be. I also hear a lot of what sounds like birdies on the upper band.
I have aligned the IF with my Motorola 1200 @ 455kc per the instructions. I should mention that I get two peaks on the IF with the slug on the 1st xfmr. One nearly all the way in, and one out quite a ways. Not sure what that's about, but using either peak does not seem to affect my problem.
Here is a schematic I posted the other day to the forum on another question I had:
http://philcoradio.com/phorum/attachment.php?aid=1749
The primary problem is this:
While attempting to adjust (with trimmer 16) the HF osc for the BC band at 1500 kcs, I can hear what I think are only images, and only two where the trimmer is nearly fully compressed.
I can not hear anything at 550 kcs, so I am unable to attempt alignment there.
Reason I think the signals I hear are images is that once I align one of them and try to hear stations on the BC band, there is nothing but static. I can however just start turning 17 out and hear BC stations going by, but if I set one dead on with 17, it is extremely wide and no other station can be heard using the tuning condensor, just that one nearly 1000 kcs wide!
Inserting the antenna does have a great effect on reception of static and strength of the BC stations I can tune in using trimmer 17.
I have measured the voltage at the grid of the XXL Osc the best I can without a VTVM, using a scope, and see only about -2 volts. Assuming that's correct, I would think it's not enough negative. What should it be? The plate voltage on the XXL Osc shows 40+ volts, and about 95 on the XXL 1st det.
The real mystery is where I find the LO using a ICOM 746. I can only find one. Setting the tuning condensor at the top of the band, about 1700, the LO is heard at 1292 kcs, and at the bottom, about 550 kcs, the LO is heard at 1244 kcs.
I'm at a loss at this point. Only thing I haven't done is replace tube sockets.
Since I have temporarily removed the push button assy., I can not check it, but my next step might be to re-install it to see if I can get them to work with thier own tuned circuits.
Yes, I have inspected my replacements, caps, resistors, and wire just in case I tied something to the wrong terminal, but I plan to go over it once more since I'm just not getting anywhere with this. I hope my lengthy description covered everything and makes some sense.
Any help will certainly be appreciated and very welcome. I just feel like I've hit a brick wall.
TIA
Brian
