Philco 38-5 - Printable Version

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+--- Thread: Philco 38-5 (/showthread.php?tid=21112)

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Philco 38-5 - Dirk van der Berg - 03-26-2020

Hi all, first time restoring a Philco 38-5. The set was partly recapped before and i did replaced wax caps under the chassis. I can hear the oscillator on nearby radio on my workbench but cannot pick up any stations on the Philco.   I have not checked inside the black ceramics under the chassis. How do you open them ? any pointers will be greatly appreciated.  

Regards
Dirk

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RE: Philco 38-5 - mikethedruid - 03-26-2020

Those are called "condenser blocks." (or capacitor blocks to use the new fangled term) Look at your schematic to figure out what condensers are inside each block. Also look at the parts list in the documentation to find the part number for each block. (for instance the block numbered 50 in the parts list is a 8326SU)  here is a link to the Philco service documentation found in the library of the main site here:
https://philcoradio.com/library/download/service%20info/wiring%20diagrams/vol2/split/Part36-Philco%20Wiring%20Diagrams%20Vol.%202.pdf
Here is a link to the information on the various blocks, their circuit diagrams, and what is inside them:
https://philcoradio.com/library/index.php/parts/bakelite-block-condensers/
You attack them as follows. First, carefully remove all the wires connected to them and mark each wire, making a diagram so you can re-attach them correctly when the work is all finished. Next, make a little aluminum foil tray, or use an aluminum disposable pie plate. Make little aluminum foil rolls to support the block off the tray, and put the block on the rolls with the tar side down. Bake in a 250 F oven for about an hour so the tar melts out and flows into the tray. While the block is still warm so the remaining tar has not hardened, pull out the guts. With your soldering iron, remove the remains of the little wires from the holes in the rivets that hold on the terminals. Install new condensers and/or resistors into the block. Do any internal interconnections between the parts before you install them. Run the appropriate leads up through the appropriate rivets, and re-solder on the top of the block. Pad the inside with a little crumpled plastic wrap, and top off with either remelted tar (if you saved it) or some black RTV. Then re-install the block according to the diagram you made earlier. NOTE, I was not able to find the part numbers for block 50, and the other 2 blocks have a different suffix, OSG and OSU, an O added before the SG and SU shown in the parts list. You should be able to figure it out from the schematic anyway. I hope this helps.

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RE: Philco 38-5 - Dirk van der Berg - 03-27-2020

Thank you very much for the information and links. I got it going now ! Found dry joint on one of valves. Must do the alignment and the cabinet need attention. 

Regards

Dirk

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