I don¡¯t have the answer to that. I did, however, throw out some carbon resistors recently (and I¡¯m in an ongoing process with my stock, which dates back decades) that were grossly out of spec, even for 10 or 20% parts. Those were probably from the 1930s, judging by their appearance.?
My stock came back to me from my friend Brent, W1IA (SK), who had received them from me in 2006, when I moved. I got them from a co-worker in the 1980s, and they belonged to his dad, who was a TV repairman, so most of the parts are at least 37 years old. Other parts had been added over the years by Brent and me.?
Most of the parts look more ¡°modern¡± and most of those are still good, so far.?
Not all of the resistors in our Drakes have gone out of tolerance. The parts are affected by time, use, storage environment and other factors.?
I tend to only start measuring components when something is not working right or if I need to adjust a pot or cap to its extreme value. One could go crazy worrying about the parts, so we have to invest a certain amount of ¡°faith¡± that the parts inside are ¡°close enough¡±.?
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
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On Thu, Mar 16, 2023 at 12:26, Bill Leonard N0CU <
billincolo73@...> wrote:
Steve,
I agree. This is more of a temporary fix for me. Once I get everything working I will go back and replace them with new parts.
What I don't remember is what is the drift profile of carbon comp resistors. Does continue indefinitely at a fairly constant rate or does it level off. If it is the latter, then I am not sure whether replacing them is necessary.
On Thu, Mar 16, 2023 at 9:56?AM Steve Wedge, W1ES/4 via <w1es=
[email protected]> wrote:
The problem with that with respect to the cathode and screen resistors is that the out of tolerance parts will continue to drift out of tolerance. It¡¯s best to use new replacements of the original value.
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
Sent from Proton Mail for iOS
On Thu, Mar 16, 2023 at 11:09 AM, Bill Leonard N0CU <
billincolo73@...> wrote:
Since I have several boxes full of resistors, I have simply been measuring the starting resistance and calculating what parallel resistance is needed. I trimmed the meter shunt to 1% and matched the cathode and grid resistor to 1-2%.
On Wed, Mar 15, 2023 at 8:58?PM Doug Crompton WA3DSP <
wa3dsp@...> wrote:
There is NO reason these resistors need to be 1%. 5 or even 10% are fine and you can always select from a stash to match them if that is your thing. They don't even need to be exactly the specified resistance, as long as it is close and they are reasonably matched. Someone put 10 ohm 2W cathode resistors in my T4XC. That vaue would probably be more likely to be found. The only resistor that might benefit from being 1% is the 3.3 ohm meter shunt, but that is also a stretch given the accuracy of the meter itself.
--
Doug, WA3DSP
