How do I remove cover of bass choke on Philharmonic?

[Ken Carr]

I was doing real well at checking the voltages on the Philharmonic amplifier. The rectifiers and the 6L6's were testing right on or 5% off.

Then I smelled something smoking in the receiver.

I believe I smoked the bass choke (that's what I think it is). This is located inside the rectangular chrome cover on the left of the receiver chassis (see attached photo).

I tried to unscrew the screws on its sides. One just turns in place and the other is all but impossible to reach with a screwdriver. I'd like to get this off with as little fuss as possible.

So, does someone know the best way to remove this chrome cover so I can get in there and look around?

Thanks.

[Norman S Braithwaite]

I know you don't want to hear this but you will have to go under the chassis, mark and disconnect the wires entering the choke assembly then remove the nuts holding the entire assembly on the chassis.  Once the entire assembly has been removed, you can remove the two machine screws on the side of the shield and if the chokes and components are nice, they will slide out.  More likely, they will be somewhat stuck inside the shield can by wax (but not potted).  You will find two chokes and four wax-paper capacitors the latter of which should be replaced (even if good if you have gone to the effort to get this far).

Norman

[Ken Carr]

Norman,

Thanks for the instructions.

I didn't expect simple, but one can only hope. I will do exactly as you said (once I get the time).

At least I know that I am not wasting my time. I just didn't want to wander around any more than necessary.

Things were going along so nicely!

For now I have to switch over to an old RCA from 1937. It works fine but I have promised it to my son-in-law. I want to do a recap before he gets it so as to avoid problems.

Have a great New Year! Your help is always appreciated.

Ken Carr, KE1RI
Norman S Braithwaite said:

I know you don't want to hear this but you will have to go under the chassis, mark and disconnect the wires entering the choke assembly then remove the nuts holding the entire assembly on the chassis.  Once the entire assembly has been removed, you can remove the two machine screws on the side of the shield and if the chokes and components are nice, they will slide out.  More likely, they will be somewhat stuck inside the shield can by wax (but not potted).  You will find two chokes and four wax-paper capacitors the latter of which should be replaced (even if good if you have gone to the effort to get this far).

Norman

[jimmie o. ashabraner]

  most likely the .o5 caps are shorted and have become a problem shorting the choke windings. my philharmonic did the same thing, was lucky chokes were not burned out. after replacing the .05 voltages stabilized, chokes ran cool and after a 4 hour on time the set performed very well, good luck on yours, jimmie

 

ps these guys on this site are very helpful and knowledgeable on the old scott sets

[David C. Poland]

Did this many years ago. There are 4 caps with the coils inside the tone reactor assembly to replace. C-40 and C-45 on the diagram.

Follow the wires under the chassis out of the tone reactor unit and unsolder them. Take good notes and make a sketch. Then dismount the unit from underneath as I recall. Hope your dual bass control pot is still ok.

Don't forget the 7 caps inside the soldered metal box mounted on the chassis inside below the 6L7's.

[Ken Carr]

Jimmie , David, and Norman,,

Thanks for the additional instructions. I will go at this carefully and with success. I always take photos, make drawings, and tag items. I never depend on my memory; it never amounted to much and now at 64 I'm lucky if I recognize my wife each morning.
Your hints and encouragement are just what I need. Thanks so much!

[Joe Miller]

Hi Ken,

I just completed this same repair. Be sure to check your bass control pot (it is a dual pot, one at 1 meg and 1 at 10K)  My 10K pot was open and I am looking for a replacement. For now, I have hard-wired a 3.9K resistor in place of the 10K pot.  I now have a low frequency oscillation with the bass control full on.  I will be trouble shooting that later this week.

Once you get your repair done I would appreciate hearing how your bass works, i.e. do you have the low frequency oscillation, does your control provide much incremental bass (mine doesn't)

Joe

[Ken Carr]

Thanks for the heads up, Joe. I have already replaced the capacitors in the unit but have not checked the values on the pot. I will check that. It will be a while before I report on the sound. This is a non-working radio at present. I am currently dealing with re-wiring the voltage divider.


< hearing how your bass works, i.e. do you have the low frequency oscillation, does your control provide much incremental bass (mine doesn't)

Joe

[Ken Carr]

Joe,

I know this is a really late reply (a full year) but I had forgotten that you asked how my bass came out. So, just for the record:

Originally any time I touched the bass control it was erratic. I would get sudden wide variations in volume. It was a mess and there was no appreciable change in bass. After finally replacing every capacitor in the radio (hidden and not) I gave the bass control pot some good squirts with contact cleaner. Unfortunately I had totally forgotten your recommendation that I test the resistances and I closed the radio up and transported it from the basement to the second floor (one piece at a time). I won't be moving it for a while. The bass appears to work. There are no sudden scratchy sounds. When I turn it up the change in bass is most pronounced at both ends. At the top end (clockwise) I can easily hear the the "thrum, thrum" that is picked out in the music. On the lower end (counterclockwise) the sound is sort of flat. So, it appears to be working.

Joe Miller said:

Hi Ken,

I just completed this same repair. Be sure to check your bass control pot (it is a dual pot, one at 1 meg and 1 at 10K)  My 10K pot was open and I am looking for a replacement. For now, I have hard-wired a 3.9K resistor in place of the 10K pot.  I now have a low frequency oscillation with the bass control full on.  I will be trouble shooting that later this week.

Once you get your repair done I would appreciate hearing how your bass works, i.e. do you have the low frequency oscillation, does your control provide much incremental bass (mine doesn't)

Joe

[Scott Seickel]

Glad you bass works ok Ken. 

I think Joe traced his low frequency oscillation problem to a bad 6J5. 

[Joe Miller]

Yes, it was a bad 6J5 tube.

[Ken Carr]

Very good, guys. Thanks for the update.