Scott Philharmonic--started restoration--need some help

[Mark Kaplan]

I finally have gotten up the courage to start working on my 30 tube Scott Philharmonic BOL radio that I got last year.  I asked some initial questions last year but now I'm finally starting to work on the amp and chassis.

I'm starting with the amp/power supply first.   It looks relatively untouched but I found discrepencies with schematics that I have.  My amp uses dual 5Z3 rectifier  tubes.  Schematic shows input cap should be 30uF but the can capacitor mounted on top of the amp is a 4uF, 600V.  I believe it to be a replacement  because it is different than the other three but I'm puzzled about the low value.  Should I go back to a 30uF, 500V capacitor?

I also started removing tubes from the radio chassis.  I ran into one puzzle (so far).  The 6B8G tube in the record scratch supressor circuit has been replaced with a 6SN7 and the grid cap wire that would have gone to the top of the 6B8G is gone.  Any thoughts on this?  The 6SN7 is a dual triode while the 6B8 is a pentode/dual diode tube.  I'm no electronics expert but they don't seem to be the same??

Thanks for any advice as I start this adventure.

[Norman S Braithwaite]

Yes, the tuner cover is heavy and it is somewhat friction fit over the tuner.  The cover is lined with lead sheet that is not always flat against the inside of the cover and therefore presses against the tuner frame.  Practical IF alignment instructions can be found at http://ehscott.ning.com/photo/albums/am-philharmonic-alignment.  They are the same as recommended by the E.H. Scott Radio Laboratories but written in common English rather than obtuse confusification language. You may substitute a VTVM or high impedance VOM in place of the microammeter.  The former instruments were not available when the obtuse confusification was written.

Norman

[Mark Kaplan]

Hi Scott,

Well, I found the instruction manual for the 9 knob Philharmonic but nothing about alignment in that manual.

I also found Norm's 5 pages of photos with annotation.   I may be having a "senior moment" but I can't find a technical manual which says anything about alignment instructions??

Thanks for your patience,

Mark

Scott Seickel said:

There is nothing attached to the cover.  Just push the grid wires thru. 

There is a technical manual in the archive section of this site that tells the alignment instructions.  Norman also posted some alignment instructions there.  Click Archive in the upper right of this page. 

[Norman S Braithwaite]

The technical service manual can be found at the link below.

https://drive.google.com/folderview?id=0B0K3TBSz_27rN2E5MTBhY2YtZWF...

Norman

[Mark Kaplan]

Hi Norm,

I've been to that link for the manuals but the 9 knob Philharmonic instruction manual doesn't seem to have alignment instructions in it.  I went to  your folder and printed the 5 pages but it would be helpful to me to have some step by step directions I  hoped to find in a technical service manual.  I don't see a technical service manual at that link??

Norman S Braithwaite said:

The technical service manual can be found at the link below.

https://drive.google.com/folderview?id=0B0K3TBSz_27rN2E5MTBhY2YtZWF...

Norman

[Mark Kaplan]

OK, maybe I found the technical service manual.  Is the "Scott Philharmonic XXX receiver" technical manual the same as the nine knob beam of light receiver?  If so, I think it was the XXX designation that threw me.   When I look in that technical manual I do see info on alignment, etc....

Thanks again,

Mark

[David C. Poland]

Think of the XXX a Roman Numeral for 30 for the 30 tube AM Philharmonic.  Same for the 12 tube Super XII, fifteen tube Alwave Fifteen  XV, etc.

Agree, cut off the grid wires and thread new wire when reinstalling the coil covers and tuning cap cover.

In recapping, the top left rear rectangular chrome tone reactor case (between the 3 audio 6J5's and the pair of 6L7 expander tubes) - inside are 4 caps to replace, and failure to do so could lead to damaged bass control.

Below that reactor riveted to the side of the chassis - a soldered medal box-  has 7 caps inside, all .05 MFD as I recall.

[Mark Kaplan]

David,

Thanks for your suggestions.  I've found the soldered metal box with the 7 caps inside (my schematic shows them as 0.5MFD, 200V  400V) but I didn't know about the tone reactor case.  I will look for it. This set , is absolutely loaded with paper caps and many of them were replaced at some point and with different values than shown on the schematic.  It almost looks like the repairman? used whatever he had available that was somewhat close; like using 0.03UF instead of 0.01UF.  Many of the replacements are old black beauty caps and I'm finding that some I've removed are still OK as far as leakage goes but others are very leaky....

OK, I found the chrome case and I see four wires coming out into the bottom of the chassis.  I think I found it on the circuit diagram;  four 0.02UF caps with two associated coils and wires going to the bass control?   Do you recall if those caps are potted in tar or can I get to them by removing the chrome case cover on the top of the chassis?  That would certainly make life easier...Thanks,  Mark

[Scott Seickel]

No, it is not potted Mark.  It looks like this:

Label the wires before you pull them out. 

Plan calls for a pair of .02 and a pair of .025 caps.  I think most have replaced all with .022 and all worked fine.

Someday when I have a chance I would like to run a SPICE LT simulation to see how big of a difference there may or may not be in the response. 

[Mark Kaplan]

Thanks Scott, that's very clear.  Appreciate the photo.  Right now I've got the chassis upside down on my bench on a big sheet of styrofoam.  Slowly replacing the capacitors underneath the chassis.  Once I get that done I'll flip the chassis and start removing the cans on the top.

[Norman S Braithwaite]

Scott Seickel said:

Plan calls for a pair of .02 and a pair of .025 caps.  I think most have replaced all with .022 and all worked fine.

No, replacing all four capacitors with 0.022 will not work.  The trap will not be tuned to the remnant hum from the power supply and will allow hum through the very sensitive expander circuits.  The radio will work but with some hum.  This subject has been discussed on this forum recently.

Norman

[Scott Seickel]

Without digging thru the archives, I believe the solution was to measure thru a bunch of caps and find a pair that measured high, and a pair that measured low. It may be possible to find NOS film caps that are a better fit value wise. I don't think you can get new stock in these values, but I have not looked.

[Norman S Braithwaite]

These values are available from www.justradios.com.  However, I used 0.022-mfd capacitors that measured 0.021 and 0.027-mfd capacitors that measured 0.026.

Norman