Pointer Dial Philharmonic Selectivity Trimmers

[Don Jackson]

Can someone verify the correct orientation of the selectivity trimmers in an early pointer dial Philharmonic? In my set the trimmer closest to the front of the set is meshed when the selectivity / fidelity control is fully counter clockwise. In this position, from front to back the trimmers are meshed, unmeshed, meshed and unmeshed. Is this correct?

The volume control has been replaced and I wounder if someone removed the fidelity control during the process and messed things up. The set was recapped at some point in the past and plays, but could be better. The set only works when the fidelity control is near the full clockwise position, when you turn the control to the left it dies out. I assume it is way out of alignment but want to check everything before attempting to align. I am planning to replace the volume control with a tapped unit so this would be a good opportunity to check operation of the selectivity / fidelity control or repair.

[David C. Poland]

Be sure the bass tones assembly has 4 new caps inside. Leaking caps make for scratchy bass control action and can destroy the dual pot bass control. It is the rectangular chromed topside metal box between the 3rd audio 6J5's on the rear corner and the pair of 6L7's in the expander circuit. Contains 2 chokes and 4 caps. Have to unwire it and then extract the thing. 

see photo example: IMG_1345.JPG

[Don Jackson]

Thank you all for your comments. I agree with Norman, the problem could be that someone aligned the set with the selectivity-fidelity control in full clockwise position. I am convinced now that the air capacitors are in the correct positions. What threw me off was the bandpass switch in the middle of the shaft.

Someone had connected the 0.15 cap to the wrong lug on the switch. I could not make any sense of how the switch operated with the cap connected to this lug and thought maybe that something was out of sync. I eventually found a photo in the archive that shows the cap connected to a lug on the underside of the switch. If the cap was connected there , it is easy to see that the capacitor would engage as the selectivity control was advanced CCW and toggle between the the 2 coils as maximum sensitivity was approached. Someone actually cut the shielded cables at the partition to the RF section, and snipped them off at the coils for reasons unknown. The photo I found in the archive shows where the cables should be connected.  I don't think this is the problem but something that should be corrected. I will check the set screws on the air caps. I downloaded the correct schematic and manual, and made a copy of the alignment instructions.  I will continue checking everything in the set and proceed with alignment. And David, the choke, resistor and 1 uf capacitor for the tapped volume control are still there, someone kindly rolled up the wire for the tap and stuffed it in a corner. The original bathtub cap was disposed of. The metal box for the 7 -.5 caps was tossed as well. This wont be a perfect restoration but should perform well when I get the bugs out. I am hoping the tapped pot will give a bit more bass at low volume.

[David C. Poland]

regarding re-introducing a tapped volume control, that tap then connects to a resistor and cap to ground - which parts hopefully are still nearby, secured to an internal metal partition.

[Norman S Braithwaite]

The symptom you are describing may be due to the IF amplifier having been aligned with the selectively-fidelity control full clockwise rather than full counterclockwise.  Before checking alignment, loosen and re tighten the set screws on the variable selectivity rotors to insure good ground connections.

[Kent King]

Fast answer: Each capacitor is opposite- exactly as you described you found it. That always throws people, and we get this question about once every 3 or 4 years. That set looks good inside, you should have a find player when you get done.

Kent

[David C. Poland]

Set screws to secure those sets of detuning air caps can loosen and cause those pairs of air caps to shift on that long shaft. Refer to the Technical Service Data page 2, paragraph titled I F section, mid page. Available in the set folder for the Philharmonic. (Similar information for the AW-23 High Fidelity model)

The concept:

As I recall, With the fidelity control full counter clockwise, each of them should be oriented the same way on that shaft. The IF amp is aligned in this condition which is the narrowest band width (low fidelity) to peak the IF amplifier.

Then, when the  IF coils are wired correctly, when fidelity control is advanced the first and 3rd pair should detune the that IF stage one way and the 2nd and 4th pair detune the opposite way. The idea is to widen the IF amp band width with staggered I.F. detuning for progressively higher fidelity  reception as the fidelity control is advanced. 

Hopefully, someone with a decent parts chassis or happens to have one on the bench will be able to help with specific info on the correct positioning of the air caps in the narrow band width position. If these air caps are badly positioned, reception would be terrible and throw each IF stage further out of alignment as the control is advanced.  Incidentally, there should be a metal cover for each pair of air caps for shielding.