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finding plate voltage drop


mopardave

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15 hours ago, NOSValves said:

What is the color bands on those resistors? It looks like its Brown/Black/Black which = 10 ohms not 1 ohm. I think your reading 1 ohm because its shunted off by the built in meter which has to have pretty low internal resistance. I'm shocked it has 1 ohm or more.... I've never seen one that wasn't at or real near zero. 

 

    In the end as long as that built in meter is connected to the cathode you can not measure with any meter. When you measured .650 or whatever is was that was .650 of 1 single mA you can't pile meter on top of meter on top of a resistor. All 3 devices were splitting the current running through the tubes cathode.  I believe the 10 ohm resistor is there to allow the tube to still work if the meter fails shorting open. The built in meter is shunting the 10 ohm resistor down to the single ohm so most of the current is running through the meter. As the Italians would say use the onboard meters and forgetaboutit. 

Looks like brown black black silver brown, but I will confirm when I get the new tubes I ordered.  When measuring that resistor I get 1.2 to 1.4, it will change from time to time, but usually 1.2 .     It may be a 10 ohm resistor.   It measures nothing like the other amp that's why I was having such trouble figuring the multimeters and the amp and not really knowing what im doing anyway.

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1st band Brown =1

2nd band Black =0

3rd band Black =X1

 

So 10 X 1 =10 Ohms

 

4th band Silver = 10% Tolerance

5th band Brown = voltage rating but I don't have a chart handy at the moment

 

 The only real way you can check the accuracy of the built in meters would be to unhook one of there wires. Than remeasure the resistor value and than measure the voltage on the resistor after the amp is warmed up. Use the ohms law to figure out what the voltage equates to mA wise. 

 

 All pretty anal retentive since the meters have to be fairly close.

 The measurements you took so far are totally inaccurate and unreliable.

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3 minutes ago, NOSValves said:

1st band Brown =1

2nd band Black =0

3rd band Black =X1

 

So 10 X 1 =10 Ohms

 

4th band Silver = 10% Tolerance

5th band Brown = voltage rating but I don't have a chart handy at the moment

 

 The only real way you can check the accuracy of the built in meters would be to unhook one of there wires. Than remeasure the resistor value and than measure the voltage on the resistor after the amp is warmed up. Use the ohms law to figure out what the voltage equates to mA wise. 

 

 All pretty anal retentive since the meters have to be fairly close.

 The measurements you took so far are totally inaccurate and unreliable.

Ok.  Thanks for figuring that out Craig.  I'll just use the meters for biasing as they were 1 of the selling points of this amp.  Simple bias adjustments are nice.

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3 hours ago, tube fanatic said:

See Dave, if you had built one of my designs you would have been enjoying your music all of this time instead of worrying about a few milliamps !😁

 

Maynard

Hahaha, yeah.  I'm good.  I will say, for 500 bucks this little amp rocks.  Gonna start rolling some tubes thru it soon.  Thanks

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