Philco 15DX restoration - Printable Version

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+--- Thread: Philco 15DX restoration (/showthread.php?tid=4706)

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RE: Philco 15DX restoration - PhilcoMike - 05-10-2012

Great work. You should be proud of your efforts!

Thanks

Mike

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RE: Philco 15DX restoration - Bob Andersen - 05-11-2012

Thanks. I've progressed over to this corner without incident until now.
I found several circuit modifications in this area, but I don't think this broken solder connection was intentional.
I'm going to restore the wiring and component values to match the schematic.
[Image: http://farm8.staticflickr.com/7104/7174693860_ac182b21ce_z.jpg]

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RE: Philco 15DX restoration - Arran - 05-11-2012

(05-11-2012, 12:45 AM)bandersen Wrote:  Thanks. I've progressed over to this corner without incident until now.
I found several circuit modifications in this area, but I don't think this broken solder connection was intentional.
I'm going to restore the wiring and component values to match the schematic.
[Image: http://farm8.staticflickr.com/7104/7174693860_ac182b21ce_z.jpg]

That does look like the work of a weekend radio mechanic, or a quick and dirty service shop. Something I've run into all too often, parts detatched, solder junctions floating in space, etc. This is one of the reasons that I always pull the chassis and look underneith before trying to power up the set on the variac. Initial inspection of a Stromberg and a Canadian Westinghouse set I picked up last year dissuaded me from powering those up, one had crumbling wire, the other a dangling burned flexable resistor and lots of 40 year old service work that needed checking over.
Regards
Arran

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RE: Philco 15DX restoration - codefox1 - 05-11-2012

Nightmare of dogbones. It's going to take some time to get right.

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RE: Philco 15DX restoration - Bob Andersen - 05-13-2012

I hope someone with a 15 chassis can help me out with this one.
I found this cap crudely solder across the #42 tube plates.
[Image: http://farm6.staticflickr.com/5469/7192247694_cd883a84a7_z.jpg]

I got a copy of the 15 schematic from Chuck which shows it as #57, but no value.
[Image: http://farm8.staticflickr.com/7230/7192247814_df3c483b7f_z.jpg]

The parts lists shows #57 as a 240,000 resistor across the volume control - not illustrated. There's no resistor across my volume control though.
It does list #58a as 0.002 mfd cap across the output transformer primary. Perhaps this is the capacitor in question ?
[Image: http://farm8.staticflickr.com/7105/7192247872_9f557e2de7_z.jpg]

Finally, to make matters more confusing, I dug up an original Philco schematic and it shows #57 as a resistor across the #42 grids and no cap between the plates
[Image: http://farm8.staticflickr.com/7092/7192361644_ba3ed9ec82_z.jpg]

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RE: Philco 15DX restoration - Ed Locker - 05-13-2012

http://www.nostalgiaair.org/PagesByModel/138/M0013138.pdf

Look at the changes made depending on the run number, on the bottom of the schematic page.

It mentions everything you talked about.

Hope this helps.
Ed

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RE: Philco 15DX restoration - Arran - 05-13-2012

Is there a reistor underneath that mica or micamold cap? It looks like there is something pigtailed across the leads. According to the dot code it's 200,000 mmf or picofarad, unless I misread it, so that's .0002 micrfarad, the correct value according to the schematic. Hopefully it's not paper inside but given the size it could be either paper or mica.
Regards
Arran

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RE: Philco 15DX restoration - Bob Andersen - 05-13-2012

Thanks Ed. Yes, that sure does help make sense of it all

Arran - there are two micamold caps pigtailed together and very crudely soldered in place. I'm sure it's a later addition to the set.
That makes me think my chassis is below run 22. I guess I should make the production changes mentioned then.

I just restuffed my first bakelite block with a resistor in it. I'd read about them, but never encountered one before.
I replaced the resistance wire with a modern metal film resistor.
[Image: http://farm8.staticflickr.com/7075/7192248628_14279376d2_z.jpg]

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RE: Philco 15DX restoration - Arran - 05-14-2012

Bob;
I think that I may have encountered a bakelite block with a resistor in it but I'm not sure, they mostly prefered to connect them on the outside. I have run into ones with a pair of micas potted on the inside fo a tone control or some such thing, it was a while ago mind you. Opps, I misread the schematic, it was .002 not .0002, or a fraction of what it is supposed to be, what value of micamold did the parallel onto the backside?
Regards
Arran

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RE: Philco 15DX restoration - Bob Andersen - 05-14-2012

I haven't separated them yet, but I put them on a cap tester and got around 0.0018 and no leakage. Even so, I think I'll replace them with a modern 0.0022 poly cap.

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RE: Philco 15DX restoration - codefox1 - 05-14-2012

Yes, that would be fine. It's there to quash high frequency oscillations. Use at least 1000 volt type. Better yet 1600 volt. Dress the same as the old one.

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RE: Philco 15DX restoration - Bob Andersen - 05-15-2012

I have a 1,600 volt orange drop on the way

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RE: Philco 15DX restoration - Bob Andersen - 05-16-2012

I checked out the volume control tonight and the resistance varies from 0 to about 1.7 M. The schematic doesn't specify a value but 6694 matches the parts list. Does anyone know if 1.7 M is in the right ballpark ?
[Image: http://farm8.staticflickr.com/7089/7207612406_070b11c4e2_z.jpg]

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RE: Philco 15DX restoration - Ron Ramirez - 05-16-2012

I can't find 6694 in any of my early-mid 1930s Philco parts catalogs. They call for either 7050 or 8054.

Only the value for 8054 is given, 350K.

The 1946 catalog specified either 45-5013 (350K, linear taper) for early models or 45-5011 (350K, audio taper, tap at 70K) for later models.

I think we can conclude from this that the value should be 350K, not 1.7 meg.

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RE: Philco 15DX restoration - Bob Andersen - 05-16-2012

Thanks for the info. I'll unmount it for a closer inspection. Maybe a little contact cleaner will help ?

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