Wire wound Resistor??HELP

[dumbassbob]

That is it My test button on mine looks different more like you see on a Wha pedal..But that big "sand" resistor is Right on..My Tube Tester looks like someone who didn't know what he was doing tried to fix it up..I am missing that sand resistor on the test switch So the Short test light has never worked..All my tester was good for was to tell me if I had a dead or bad tube...And I could see how much I had used a tube...I am a good guitar player and have learned enough on this and a few other sites to keep my old Fender and Marshall amps working..Like yesterday I was getting a whistle when I turned my SD-1 on..My tubes were microphonic...All it was a bad patch chord from my wha to the SD-1 OD....And living at the beach you Have too keep your gear Clean The salt air and wind blow dirt and salt into everything,even covered....If anyone Know what that big Reddish looking resistor is...Big Help to DAB...Thanks for finding the PIX

[olddawg]

Can you be specific about what values you tried?



Well 819 ohms isn't many ohms. And as Juan speculated it may be appropriate for a variable cathode circuit. If that is the case a straight wire may have "pegged" the meter (though we don't know the context) because of excessive current in the tube under test. Resistor values in k ranges may not allow enough current to register. If you haven't tried something as low as 820 ohms then you haven't actually made a reasonable replacement attempt.

You mentioned that you couldn't get a good reading on the resistor after the repair. But if it's "working" in the circuit then you should be able to test it's value in circuit and get a steady reading. This may require some figuring to determine it's value in circuit context.

If you can solder it in circuit you should be able to solder some wires with banana plugs on the ends to plug into a meter. I've done this before to get a stable reading on low resistance components. Like was said. You probably won't be able to solder directly to nichrome wire but you should be able to get a stable connection for test. You could also measure the voltage drop across it in circuit and calculate the resistance?

[J M Fahey]

You might make a brute force ohmeter
Why a brute force one?
Because surface oxide will easily block the 1.5V or 3V DC supplied by the multimeter, thatīs why you find such large values when measiring with a meter, but under actual (way higher) use voltage it perforates the grime.

I suggest you get some DC supply, say from 15V to 30V or thereabouts, you may "steal" that voltage from some other amp or whatever you have neaby, apply said voltage to the mystery resistor , check that it does not smoke or burn a hole on your table, and if fine, connect your multimeter set to current in series with it.

Start with the "High current" setting just in case, even the cheapest meters have an unfused 10A scale and if you see itīs less than 200 mA (the next cheap meter scale and it is fused) recheck and note value.

R=V/I

I trust this more than the actual "Ohms scale" value, go figure.
I also use it for believable low ohm measurement (under 1 ohm ballast resistors and such).

[dumbassbob]

I unhooked one end of the resistor and I think it said 04.25 MO. I have a hard time seeing small things.Ever since I was hurt 25 yrs ago I stopped breathing for 4-5 minutes and I was empaled threw my leg when I fell 2 stories So I am Slow...It broke its leads off 3 times,I was able to get it back on..Right or wrong my tubes are reading the same as before ..But I do not know the wattage of the resistor...

[The Dude]

...... it simply canīt be trusted......Get a new resistor... and replace it......

^^^^THAT