[morzh]

I have a couple of resistors that don't read what their suppose to read, I haven't isolated them yet from the circuit and checked it without being wired in. I have a question about resistors, if one is out of range, what would you expect to hear or whatever from the radio. Would I notice if one was out of range?

One of the things that I'm having trouble with right now as I check all the resistors and capacitors is identifying which one I'm testing. I look at the parts sheet that shows me where in the radio it is, but there are also a lot of other "parts" that look the same in the same spot in the radio. The schematics help some on tracing which one is which, but it can be very confusing.

Jeff

Jeff

About resistors and caps:

1. ALWAYS check your parts when the power is OFF and it has been OFF for awhile.
2. The ONLY guarantee you are having a real reading is when the part is isolated from the rest of the circuit: for both types it is achieved by unsoldering one end. The other may stay connected.
3. With resistors, if the value you are reading before you isolated the part, is noticeably higher than what it is supposed to be, it is a sure sign of the part being bad.
The reason is, the rest of the circuitry is in PARALLEL with the part, and the ONLY thing it can do is to LOWER the reading, so if it is higher than the part is WAY OFF.
Still, unsolder one end - this will take the guesswork out of the process.

4. With capacitors it is quite uncertain while in circuitry, and you are likely to have unrealistic reading unless it is disconnected.

5. I don't know the old tolerances, but I would allow 5% for resistors and 10-20% for capacitors, as this is what it is today. (I mean, there are 0.1% resistors and sub-1% NPO/COG capacitors, but those are not one would use in a radio anyway).

6. Even if your old paper capacitor works, it is likely to actually gain capacitance (mine were 2x-3x times the nominal value) and develop some leakage. The common wisdom, even if all is working, is to replace them all, with possible exception of mica types, as mica is a mineral and does not age so badly. But Electrolytics and papers should go.


My own experience (small enough with antique tube devices, as I restored just one radio, but then I am an EE with 30 years industry experience, and done some tube amps when I was a kid, in 70-s) is: all my resistors (they were carbon type) have gone up in value up to 2x - 2.5x times, and it is bad, as it will screw up your DC regime, and all paper capacitors were 2x-3x the value, and some were asymmetrical when measured with regular C-meter, which indicates a leakage.

Mike.