While aligning this radio the IF is fine, the 1400KHz frequency is fine but the 580 kHz cannot be adjusted. I hear the signal in the full range of the tuner. Adjusting the compensator has no effect at all I disconnected the compensator for the 580 kHz adjustment and checked it with a meter and a digital cap checker. It is not shorted, and it can adjust between 350pf-900pf. Does anyone know what the range of this compensator (number 19 on the schematic part number 31-6298) should read?
Not familiar with this radio, but looking at the schematic for part 19 - check the ohms on all three coil sections there and toggle the switch in/out to check each way as indicated on the schematic at this point (A6? - hard to read on my copy). I did not find this trimmer in the 37 philco catalog, but seek out all parts catalogs you can find on the web to see if you find it.
I believe there may be an error on the schematic or the alignment procedure of the 40-180 service info. Looking at the schematic, it appears that the 580 kc adjustment should be trimmer 19A instead of 19. This would make sense since adjusting 19 has no effect at 580 kc, yet when you measure the cap it does vary from 350 to 900 pF.
I looked also at the service info for the 40-165 which uses a similar circuit and the corresponding trimmers (26 and 26A) are reversed in the alignment procedure.
Try adjusting 19A at 580 kc and see if it has the proper effect.
Thanks for the information. This radio has previously been worked on. I did check the wiring from the selector switch and pin 2 of the oscillator is connected to what the schematic has as Compensator #19 and A2 of the switch. Pin 4 of the oscillator is connected to compensator 19A and pins A5&6 of the switch. I will adjust it assuming the wiring is correct, and that schematic is mislabeled.
OK I readjusted the 1400 Hz signal by a delicate balance of adjusting 19A and 19. The 580 Hz is still constant throughout the range of the tuning dial. I have tried to readjust 19 and then went back to 19A it does not matter. I will disconnect 19A and take a reading on the compensator.
Considering how the oscillator circuit is designed, the trimmer labeled 19A which is connected to switch pins A5,A6 would be the LF padder adjustment at 580 kc. It typically has a set capacitance of about 700 pF, which is right in the range of the 350 to 900 you measured.
The other section of the trimmer 19 connected to switch pin A2, is the HF adjustment at 1400 kc. It should have a much smaller capacitance as it is effectively in parallel with the tuning cap in broadcast band position and should have a significant effect only at the high end of the band.
When you measured the capacitance of the trimmer, did you measure both sections and did the readings differ?
Given there is some error in the labeling of trimmers 19 and 19A it may be confusing as to which is which. In any case, the trimmer section measuring 350 to 900 pF should be connected to A5, A6 and pin 4 of the coil, and should be the 580 kc adjustment.
The trimmer labeled 19A range is 17pf-120pf, 10 300pf-900pf. Pin 4 was in fact wired to the one labeled 19A which reads the lower capacitance. I crossed the wires to connect pin 4 to the 300pf side and pin 2 to the 20pf side. I can adjust but still having some problem. Lower broadcast stains 620 - 920 come in pretty good. The high-end stations are not coming in and after my adjustment as I move the tunning dial, I pick up the 1400 signal at several points. I feel I am getting close but still have a bug to work out.
Thanks for all the advice the radio is working much better the only issue I can see is although the 2nd IF can (37) has an adjustment (37A) it has no effect on the IF frequency - nothing changes. the IF seems be ok adjusted by 30A & 30B.
Just in the process of doing an alignment on my 40-180. So was the conclusion that was reached was that compensators 19 and 19A should be reversed on the alignment instructions, for operations 3, 4 and 5?
You really need to address the rf amp problem before doing the alignment. You could do the IF alignment but check the voltages around 1232 for a clue on the rf amp.
I will check but wouldn’t it be highly unusual to have the same issue in both of the two 40-180s I have? Further on the alignment procedure though (see pic below), I have a few questions… be gentle, I’m a newbie.
On Op 2, Note D it references the “high frequency oscillator compensator” … is that 21A?
On Op 3,4,5 there was a March 2022 thread that suggested the labelling of 19 and 19A should be reversed. I will make that change.
In the paragraph above the table under SIGNAL GENERATOR, last line, it states “It is necessary when adjusting the padders that the receiver be left in the cabinet”. Do you think that it should have read “that the receiver LOOP be left in the cabinet”?
Finally, I assume that both the SW receiver loop under the top of the cabinet and the statically shielded loop antenna (ie the brown paper cylinder in the lower portion of the cabinet; see example pic below) should both be connected when doing the alignment.
>I will check but wouldn’t it be highly unusual to have the same issue in both of the two 40-180s I have?
Have troubleshot several sets w/that choke being open.
>On Op 2, Note D it references the “high frequency oscillator compensator” … is that 21A?
Yes it sets the high end of the top SW band.
>In the paragraph above the table under SIGNAL GENERATOR, last line, it states “It is necessary when adjusting the padders that the receiver be left in the cabinet”. Do you think that it should have read “that the receiver LOOP be left in the cabinet”?
Not sure. May require short adjustment tools to make the adjustments while in the cabinet.
>Finally, I assume that both the SW receiver loop under the top of the cabinet and the statically shielded loop antenna (ie the brown paper cylinder in the lower portion of the cabinet; see example pic below) should both be connected when doing the alignment.
You assume correctly.
Checked voltages in and around tubes 1234 and 7J7 equivalent (now 6J8G).
By 1232, measured 162V (schematic 160V) and 115V (schematic 105V).
By 7J7/6J8G, measured 74V (schematic 80V) and 147V (schematic 150V).
Thoughts?
Checked 2nd Philco 40-180. This one appears to have an issue.
Around 1232 tube, measured 182V (160V schematic) and 179V (105V schematic).
Around 7J7 (now 6J8G), measured 161V (150V schematic) and 86V (80V schematic).
So if I need a replacement for Part 13 (RF coupling trans), where would I find? Never had to replace one before.