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Scott Philharmonic--started restoration--need some help

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.

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The capacitor should be 30uf to the best of my knowledge. 

As for the 6SN7, it looks like the circuit was messed with.  You are going to need to undo the mess. 

Is this a 7 knob BoL set? or a later 9 knob version?

Scott,  this is the 9 knob version and  you provided me with a large schematic (that you drew) last year.   Your schematic is very similar to myset except that the amp in your schematic shows octal 5U4 tubes while mine has the earlier? 4 pin 5Z3 tubes but they are about the same electrically...

Mark

OK, I've now turned the radio chassis over and first thing I notice is some extra pots? under the chassis.

Also, if you look at the rear right section you can see a very large multi tap adjustible resistor has been put in along with three electrolytic caps (120uF, 12uF and4uF , 450V)  There also is a 1 tube (6SC7) phono pre amp that has been wired into the set in this area.   I suspect the pre amp was needed for the Garrard 3 speed replacement  (1950s?) turntable mounted in the top of the cabinet.

Any suggestions how to proceed.

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Here are two of the possibly extra, added pots circled in red

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How to proceed?, well, if it were on my bench I would be trying to determine everything that is not original and restoring it back to original.  I know this can be difficult without a guide set.  If you had a 7 knober, I have a complete detailed drawing of where every component is and how it is wired.  I am waiting to get a clean 9 knober to do the same. 

What I see looking at your pics:

The pot on the C voltage divider is normal for that set. 

For the other pot you circled, I suggest drawing how it is wired in as you cut it out...  :-)

I personally would cut out the phono pre-amp and use a small solid state one if needed.

The multi-tap resistor look like a new B+ divider to replace the original one that should be, or was,  under the capacitor box on the upper right in your picture.  It looks like they added extra filter capacitors to various taps.  I would cut them out. 

The aluminum capacitor over the C voltage divider is not original. 

It looks like a pot was added to the front of the chassis on the lower right of your pictures.

I think there are a few fairly decent pictures of the underside of 9 knober Philharmonics on this site in the photos section, if not, I should have a couple I can send you. 

Otherwise, it looks like a fairly clean set.  :-)

Scott,

Thanks for your suggestions and help.  One problem I  am having is that the underside chassis photo in Riders vol. 14 for the Scott Philharmonic is different than my set so it is difficult for me to tell what has been done and even what individual components are.   I'll do my best to trace things out but I am far from an expert here.

Mark

Yeah, the Riders pic is the 7 knob version.  It also is not of good quality. 

Friend me here so you can send me your e-mail address.  I will send you a bunch of good quality pics of the bottom of a 9 knob AM Philharmonic. 

Well, I've made some progress but I need some help.  Scott Seickel has been very kind to provide me with some photos and advice. Here is where I am:   I've rebuilt the power supply/amp which was fairly straight forward as it is roomy and not terribly complicated.   On the chassis I have replaced all the electrolytics and seven 0.5uf bypass caps in a metal can part 1321.  Many other "paper" caps seem to have been changed somewhere along the way with black beauties and other brands and some look still original.

I set up the chassis, amp and speaker on my bench with a 10 ft wire antenna and sloooooowly powered up the set using a Variac.   The good news:   The set plays on AM (at least my three local stations) with lots of volume and good fidelity.  Basic controls for selectivity and sensitivity seem to work as does the tuning eye tube.

The bad news:  I only get some static on all of the short wave stations.  Can't even hear WWV out of Denver.

What should I do next?  There are a lot of paper caps I can reach and replace.  I assume some or most are leaky.

HOWEVER, and please bear with me on what may seem like a dumb question,   it seems like there are a number of capacitors attached to coils (IF and others) inside the large cylindrical covers on the chassis.   Now many of these covers have a grid cap wire coming out the side which is tightly held by a metal? or possibly hard rubber grommet.  I could remove each of the grid caps but the wires are pretty tightly held in place and I'm afraid even if I manage to push the wire through the hole in the side of the can I wouldn't be able to get it back through since there is little slack in the wire and I'm afraid of breaking the grid cap wire where it attaches to whatever coil it goes to.   If that makes sense can anyone offer some advice as to how to proceed.  Should I really attempt to replace all the paper caps I can find under the set and inside the cylindrical cans??

Thanks for your advice and help.

Mark  (neither an electronics expert or a mechanical genius)

Mark:

Replacement of all wax-paper capacitors is appropriate for good and dependable operation.  Unless there is some reason to preserve the Celenese insulated grid wires, I just cut them flush to the feed-through grommet and push the cut end in before removing the shields.  When reassembling, I use silicone rubber insulated test lead wire and install by inserting the loose end of the spool of wire through the grommet and soldering to the IF terminal.  I then set the shield can, cut the silicone insulated wire at the far end of the grid cap, strip and reinstall the grid cap.

The lack of short wave reception may be due to alignment.  The Philharmonic will pick up strong local stations and sound OK even if the IF is way out of alignment.

Also, those black cased and most of the other replaced capacitors in your set are wax-paper.  The only black molded plastic Sprague capacitors that are mylar film (difilm) are those with red printing.

Norman

Great progress Mark. 

Make sure you check all the resistors going up to the transformers while you have the cover off. 

Also, under the tuning capacitor cover (the rectangular box on top) there are a few more capacitors and resistors. 

Not an easy set to do, but at least you know now that the set is going to work as the fundamentals are in good operation condition. 

Norm, Scott,

Thanks for your advice.  I do have one more question about the tuning cap cover that Scott mentioned.  There are a number of grid cap wires coming out of that cover also.   I removed all the screws holding the cover to the chassis base  but unless the cover is unusually heavy it seems like there are components mounted to the cover?? (or not).  I don't want to push the grid cap wires through the tuning cap cover unless I'm pretty sure I can remove it to replace those wires.  I also don't want to damage anything by pulling the cover off unless I know there is nothing attached to it but the grid cap wires that I can  push through.

Also, while I am thinking about it, are there instructions available anywhere for alignment of this monster set; at least for the IF so that I could get started when I get that far.  Thanks,    Mark



Scott Seickel said:

Great progress Mark. 

Make sure you check all the resistors going up to the transformers while you have the cover off. 

Also, under the tuning capacitor cover (the rectangular box on top) there are a few more capacitors and resistors. 

Not an easy set to do, but at least you know now that the set is going to work as the fundamentals are in good operation condition. 

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. 

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