Tube Bias Checker?

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77CUSTOM
Junior tube assistant
Posts: 1
(4/1/04 11:35 am)
 Tube Bias Checker?
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 I was just wondering if someone could tell me if I need to insert a 1 ohm resistor on the cathode (pin 1and 8) of the power tube to use this or is it just plug and play so to speak.
Thank you,
Ed
 
zachsdad
Posts: 6
(4/1/04 12:25 pm)
 Tube Bias Checker
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 If you use the DC mA setting of your meter just read "straight thru". You are reading current thru the circuit. Or, you can insert the 1 ohm resister as you state but then you will need to read DC volts across the resistor and convert to amps,l i.e., if you read .034 volt on the meter this would be 34 mA.

Leslie
 
77CUSTOM
Junior tube assistant
Posts: 2
(4/1/04 12:51 pm)
 Re: Tube Bias Checker?
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 Okay that's what I thought. I'm getting a very high reading of 73 ma. I have tried using the bias checkers on another amp of mine and they worked fine. The amp I'm on now is sort of a make shift 2204. 2205 coverted to a 2204. When I got the amp back from the builder I was there when he set the bias with his scope, then he checked the voltage on pin 5, -35. This is the same -35 that I have now but I don't understand the high ma reading I'm getting.
 
zachsdad
Posts: 7
(4/1/04 3:20 pm)
 Tube Bias Checker
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 Remember the voltage (-35) is just that voltage. For the current to be correct, the cathode resistor has to be correct. Make sure the resistor hasn't changed value from the stated value.

Leslie
 
77CUSTOM
Junior tube assistant
Posts: 3
(4/2/04 10:01 am)
 Re: Tube Bias Checker
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 I'll check the value of the cathode resistor. But both output tubes are equally high in the ma range. I have to get in the amp and check the plate voltages to see where there at. I've got a busy couple of weeks coming up so I'll let you know what I come up with. Thanks for your help,

Ed
 
punkykatt
Junior tube assistant
Posts: 1
(4/8/04 1:44 pm)
 Re: Tube Bias Checker
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 Question: Can you play your amp to test the sound while having the bias checker plugged in and hooked up to the meter? Thanks, Punky
 
zachsdad
Posts: 10
(4/8/04 7:53 pm)
 Bias Checkier
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 Should be no problem. Just be careful
 
 
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