For many years test equipment had minimal safety requirements. Newer equipment often has "sacrificial" resistors in parts of the circuit that also function as fuses. They often run hot and fail without reason. Usually the prints will have a label on them, calling them a "Critical Safety Component". Could the resistor you see overheating be one of these?
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Bruce Gentry KA2IVY
On 4/29/21 17:05, Mark Vincent wrote:
Obviously this resistor is underrated in wattage. Something like 1 ow 2W would be better. If a resistor looks like this, it should be a higher wattage. I have seen this problem of a overstressed resistor go up in value or open causing the same problem you have/had. An easy way to get the power needed is to parallel or series resistors, when possible. Sometimes getting the precision resistor in the wattage needed cannot be done with one resistor. You can use an 82 ohm 1 or 2W resistor in parallel with a 4700 ohm. That will give you 80,5938.,. ohms. Well within the 1% tolerance. This is provided you use 1% resistors or measured ones. Your plug-in is worth getting right because it is a rare piece. It looks in excellent condition.