The PHILCO Phorum

Full Version: Capacitor Value and Wiring Tolerance-Am I Being tooo Fussy?
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From what other members mentioned a slight variation doesn't matter but I have reached the Cathode By-Pass for two tubes.
The value of .09uf is required or listed in the schematic and all I have is .082uf and .1uf both at 630 volts. Are both acceptable the .1 being lets say .0999 plus or minus or am I wringing my hands over such small amounts especially in the "front end" of the receiver? These are located in the Bakelite Block capacitors and are not the easiest to replace if one is too big and one is too small OR is bigger better or small better? It's this with my yellow Polypropylene or dig through a large box of bulk Disk Ceramics perhaps needlessly?
Some more info on these cathode bypass capacitors is each on is used for: 6A7 a heptode operating as frequency changer with electron coupling, and 78E listed as a variable-mu H.F. pentode operates as I.F. amplifier
Also a bit off topic but on the other hand tolerance comes to play again and this is with the wiring to these same two tubes. the 6A7 and 78E both use a guesstimation of 16 gauge wire to the cap on top while the PenDD61 uses approx. half the gauge and the wire is a feeble cotton covered thread compared to the other two. Why is there such a difference in wire gauge which is also making me paranoid on the capacitor values? The PenDD61 was that multipurpose Valve or Toob that is both detector and audio output. This tube (PenDD61) with the very light cap wire is described as Diode second detector is part of double diode output pentode and Audio-frequency component in rectified output, so the story goes from the 1936 Trader Service Sheets Icon_wtf
According to the schematic this set is equiv. to the Philco 269 with slight mods to the 444.
Yes I have a number of radios in my collection that have been sitting for years with original capacitors not replaced and as I replace these in the 444 during replacement ALL have failed tests on my Heathkit IT-11 capacitor tester miserably to the point of probably causing severe damage if I would have plugged in this radio first.
0.09uF is a nonstandard value. Either one from 0.082 uF or 0.1uF will do.
And thank you very much! I have quite a few 0.1's on hand. Now all I have to do is figure out where to get that 18-20 gauge wire which puzzles me why there is a difference in the first place.
16 gauge is too heavy, it's probably closer to 18 or 20, close because the British have their own system of wire gauges, and like Canadian Philcos they probably used locally sourced wire as opposed to importing it from the U.S. The wire Philco used on most of their pre 1939 models, in Canada and the U.S, is frequently called "Pushback Wire" 20 or 22 gauge with a fabric cover that you can push back rather then strip. Like Mike said, for capacitor values, just go with the closest industry standard value, in a yellow film cap, restuff the original cardboard shells if you want them to look authentic. The same goes for resistors, except you want the next highest standard value, but keep in mind that new resistors sometimes have voltage ratings if they are carbon film.
Regards
Arran
This is why I use mostly 1W rated resistors, they are large enough to not worry about most voltages.
Thanks and after sending out enquiries the sellers are indicating 1/8 diameter outside which will work for the speaker wiring that is all beige on top and green and other colors below. The stuffing went great including the paper tubular that giving a bit of heat to cook them I carefully roll up the curled in end and push everything out and most have a paper disk on each end. A bit of hot glue gun glue and a bit of heat and roll them back shut on the ends. Some the yellow capacitors barely fit and some like the .1 of a higher voltage had a great deal of room. The modern are higher voltage and much smaller. As for the .09, .082 vs .1 the larger size slid in like it was meant to whereas the .082 was slightly too big. Things came to a screeching halt when I arrived at those two .00011 or 110pf in one Bakelite tar block. Those I don't have and the few suppliers that do only have 100 or 120. A number of non standard sizes in this set what little there is underneath.
As for the wiring other than being exposed to wax from capacitors, 83 years of lint and nicotine, and fading above none of it is bare or crumbling so I have been leaving it in and trimming the ends as I unsolder and replace capacitors. In a pinch the wires to the speakers could be dyed green and what other colors they are perhaps using food coloring or dye from those water based felt markers because there are three colors for this wires that show up underneath. I have recapped and renewed resistors in much newer sets with little trouble for parts compared to this set. At least many of the "dog bones" are testing in the ballpark many indicating a bit less instead of much more like the newer carbon composite resistors usually do and this is taken with a grain of salt as the multimeter is offshore total garbage and was the best the local hardware store had. I will purchase a good Fluke while I'm waiting for the 110pf. Otherwise I have found ZERO capacitors that were good so far except for the few mica under the chassis. This is using my IT-11 Heathkit probably as old as I am which probably needs recalibration but is working otherwise okay using the new capacitors to confirm this.
I wouldn't get too hung up on the 110mmfd caps 100 or 120mmfd are fine in that circuit. If I'm not mistaken they are there to filter out any rf out of the audio signal just pass the detector stage.