Philco Model 38-7: what caps & resistors do fail typically? - Printable Version
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Philco Model 38-7: what caps & resistors do fail typically? (/showthread.php?tid=25845)
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Philco Model 38-7: what caps & resistors do fail typically? (/showthread.php?tid=25845)
Philco Model 38-7: what caps & resistors do fail typically? - Musaeum - 06-17-2025
Hi all,
on vacation in Montreal, a friend of mine showed me a Philco Model 38-7 console radio from the 30ies. Mechanically very sound, all original, complete, couldn't resist offering him to look after the electronics.
Now I have the chassis and the loudspeaker. I have some tools at hand (scope, multimeter, soldering iron), but no components and no variac /isolation transformer, making repair a bit tricky. Can anybody help me about what caps and resistors typcially always fail in these units? So I can do some focused shopping...
If some good soul would welcome me in his workshop in Montreal that would be great, too :-)
I'm a german electronics engineer and like to repair old stuff, TVs, Radios, measuring equipment, audio stuff... here is the most recent: https://groups.io/g/TekScopes/message/209892
cheers
Martin
RE: Philco Model 38-7: what caps & resistors do fail typically? - klondike98 - 06-17-2025
Welcome to the Phorum!
Here's the schematic for that radio from our digital library: https://philcoradio.com/library/download/service%20info/wiring%20diagrams/vol2/split/Part37-Philco%20Wiring%20Diagrams%20Vol.%202.pdf
Something to do before you start replacing caps is to check the continuity of all the various transformer coils. If one of those is open you have a bigger job than just replacing caps.
The electrolytic caps and all the paper caps will be bad and will need replacing. Resistors need to be checked to determine which are out of spec. Mica caps are usually OK.
RE: Philco Model 38-7: what caps & resistors do fail typically? - GarySP - 06-17-2025
Welcome to the Phorum, Martin! Open a new thread in Philco Electronic Restoration when you begin working on your 38-7. Lots of folks here to help you along. Post your photos and questions there. Take care, - Gary
RE: Philco Model 38-7: what caps & resistors do fail typically? - Musaeum - 06-17-2025
Good idea to check the coils... then I'll get hold of an incadescent light bulb and see what happens when the unit is switched on in series with the bulb.
I've found 3 electrolytic caps in the schematics, 2 X- (or Y-?) caps across the mains, and a bunch of paper caps mainly around the volume control.
cheers
Martin
RE: Philco Model 38-7: what caps & resistors do fail typically? - klondike98 - 06-17-2025
Yep the dim bulb test is OK but I'd definitely replace all those electrolytics before I did it. Since those #47 condensers each go to ground I would replace with Y safety caps. The #47 condenser is a 3793DG bakelite block capacitor. I've only seen this style in Philco's but its essentially a paper capacitor also. Here's a tutorial for taking the old caps out of that block and replacing with new ones although I'm not certain whether 2 new style Y caps will fit or whether you are trying to retain the look of the electronics or just replacing with new caps. (Restoration vs repair?) https://philcoradio.com/library/index.php/shop-talk/techniques/bakelite-capacitor-rebuild-without-desoldering/
...and here's some wiring data on those block capacitors: https://philcoradio.com/library/index.php/shop-talk/general/bakelite-block-data/
I usually take the block out of the set completely in order to remove the old cap and stuff in a new one.
RE: Philco Model 38-7: what caps & resistors do fail typically? - RodB - 06-17-2025
Welcome to the Phorum Martin.
I count about 9 paper caps, the 3 electrolytic caps and 2-Y2 safety caps to replace the line filter caps inside part 47 bakelite block.
RE: Philco Model 38-7: what caps & resistors do fail typically? - radiorich - 06-18-2025
Hello Martin,
Welcome aboard our little community what great Model 38-7
Sincerely Richard