The PHILCO Phorum
Model 90 B.C. Resistor - Printable Version

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Model 90 B.C. Resistor - rrova - 08-03-2018

Just working my way through a Philco Model 90 (dual 45's, March 1931) restoration. I've verified the power transformer, identified all the leads and found that the serviceman that worked on it previously had wired it incorrectly into the circuit. Also, tab 2 of the B.C. Resistor (the multi-part resistor alongside the edge of the chassis) is totally missing and the wires intended for it were tied to a terminal strip, omitting the resistor. I presume I can sub a 800 ohm 25W? resistor for that tab/section? or maybe fabricate a tab to go in that position? Any advice or suggestions?

RE: Model 90 B.C. Resistor - morzh - 08-03-2018

If you mean the #38 resistor,
http://www.philcoradio.com/images/phorum/schem/90a.jpg

Section 1-2, then yes you can. 25W is an overkill, 5-10W is enough, but if you could fit it, sure.

RE: Model 90 B.C. Resistor - Radioroslyn - 08-03-2018

You also should verfiy the rest of the resistances on #38. It may have been replaced w/a totally different resistor.

RE: Model 90 B.C. Resistor - rrova - 08-04-2018

Thanks for the suggestions. I decided to remove the BC resistor(s) entirely from the circuit. I brought out my 40x jewellers loupe and was able to find the two broken (TINY!) wires that related to tab 2. I cut out a new tab from some thin copper and was able to carefully re-solder the wires to the new tab. My luck is holding since I checked all the resistance values and they were in the ballpark. So I'm re-installing it into the chassis and re-hooking up all the connections. My new DSO should arrive tomorrow, so I'm looking forward to firing it back up and looking at signals.