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41-255 power dissipation reality check
#3

MrFixr55 Wrote:/SNIP/ It is essentially the cathode resistor for the pair of '41 output tubes / the current draw across that resistor is about 44 mA.

The resistor dissipates 0.8W. However, considering the pic of your Candohm, 3W would be prudent, especially for the 146 Ohm section.

Verify the accuracy of all resistors in that circuit, especially the 3900 Ohm resistor, R56 between the 2 screens and the 2 470 KOhm Grid Resistors, R53 and R54 for minimum distortion.


Thanks for your thoughts and suggestions; they are most helpful. I just happen to have a 3W 150 ohm resistor on hand, so that's what I'll use for the 146 ohm section. None of the resistors in the chassis were ever changed. They're all the porous type and all were out of tolerance. I've already replaced the resistors you mentioned with 1% ones that I had on hand. The previous old work consisted only of snipping some wax/paper caps and wrapping the leads of the new ones around tie points, so a lot of clean up and reworking of those as well as proper electrolytics and line filter capacitors. I'm also making the changes noted in the Philco literature for improved sensitivity and bass compensation. I lucked out on fixing the original pushbutton power switch, which failed due to one wire lead not being soldered to the copper contact inside the switch body.


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RE: 41-255 power dissipation reality check - by jtiner - 08-20-2022, 08:01 AM



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