condenser/resistor question? - Printable Version
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condenser/resistor question? - tab10672 - 05-11-2010
I am about to recap a mod. 511, what wattage should the wound resistors coupled to the (3) .1 uf /100ohm by pass condensers be repaced with after I remove and repace the .1uf half of the condenser?? I am attempting to rebuild the original part, (if possible) but if the resistor is larger than 1/2 watt I dont think there is enough room. Any input would be greatly appriciated. Thanks
Re: condenser/resistor question? - hotrod - 05-11-2010
If this is one of the Bakelite capacitors, 1/2 watt should be fine.
Rod
Re: condenser/resistor question? - tab10672 - 05-11-2010
hotrod Wrote:If this is one of the Bakelite capacitors, 1/2 watt should be fine.Well, they are not the bakelite type like in the mod. 70 onward, these are large (about 1/2" diam. X 1 1/4" long) round paper type caps with the same tar type filler as the block type. but the risistor is thin wire wound around the outside from terminal to terminal. kind of like a small coil form. Thanks, Todd
Rod
Re: condenser/resistor question? - hotrod - 05-12-2010
I know nothing about any resistors like that so hopefully Ron, Chuck or someone else who knows will chime in on this. I've seen wire warped around capacitors in Philcos before but these were use to block RF.
Rod
Re: condenser/resistor question? - exray - 05-13-2010
1/2 watt would be fine. Quick math:
Power = current squared times resistance. p/n 17 would be the worst case since it carries load for all three tubes. Figure 10ma for each tube. That's far above the worst case!
So 30ma total, or .03 amps. .03 squared is .0009. Multiply that by 100. Result is .09 watts.
These resistors aren't doing any voltage dropping to speak of. Their main purpose is to provide some isolation between the stages.
GL,
Bill
Re: condenser/resistor question? - tab10672 - 05-13-2010
exray Wrote:1/2 watt would be fine. Quick math:
Power = current squared times resistance. p/n 17 would be the worst case since it carries load for all three tubes. Figure 10ma for each tube. That's far above the worst case!
So 30ma total, or .03 amps. .03 squared is .0009. Multiply that by 100. Result is .09 watts.
These resistors aren't doing any voltage dropping to speak of. Their main purpose is to provide some isolation between the stages.
GL,
Bill
Thanks for the info, I have been collecting philco's for years but have recently started electronics restoration. I service H.V.A.C. for a living and one thing I have found is that the schematics in the heat and air equip. are accurate to if it shows a conection at a certain point that wire can be traced straight to that point but in these radio's it is harder(atleast for me) to trace a conection because it may jump across 5 different terminals/conections before reaching the point of A to B that the schematic shows. But with time I am sure I will get it down. Again, thanks for the information.
Todd
Re: condenser/resistor question? - exray - 05-13-2010
Some folks, 1930s RCAs as an example, included a pictorial parts AND wiring layout in their literature. It really is helpful for new and old alike.
You'll get used to the schematics. In the long run they make the most sense electrically with the least complexity. Err, well most of them anyway!
GL,
Bill