I think I have toasted a pair of these by applying too much heat when soldering leads to them🙁 I have 2 meters that act funny when I try to measure them and I get no sound from the amp when they are installed. Put the grid resistor back and works fine. I suspect I must have melted the internal connections to the pins. Could these be repaired or am I SOL?😱
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"You can definitely NOT TEST that coil on an induction tester. Well you can, but you get too low result."
Post your schematic where this grid choke does not work.
p.s.
The static resistance of this choke is 4k8 (2k4+2k4), the standing DC current is 800uA.
If you use 3.3V DC battery for testing, the DC current via the choke is approximately 687uA.
"You can definitely NOT TEST that coil on an induction tester. Well you can, but you get too low result."
Post your schematic where this grid choke does not work.
p.s.
The static resistance of this choke is 4k8 (2k4+2k4), the standing DC current is 800uA.
If you use 3.3V DC battery for testing, the DC current via the choke is approximately 687uA.
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Schematic?
I don't know how, but I see little point. They were being used as Lundahl intended, to replace a 470Kohm grid resistor in a 45 DHT amp, both coils in series for the specified 540H. Granted the difficulty of measuring the inductance, but surely I should at least get a continuity reading on my volt-ohm meter😕
I don't know how, but I see little point. They were being used as Lundahl intended, to replace a 470Kohm grid resistor in a 45 DHT amp, both coils in series for the specified 540H. Granted the difficulty of measuring the inductance, but surely I should at least get a continuity reading on my volt-ohm meter😕
Volt Ohm Meter.
Do you mean a VOM that has an analog meter movement?
Usually those work to measure DCR of an inductor (as long as they are not auto-ranging).
But you have to wait until the meter overcomes the inductive reactance of 540H (that is a long time constant for most VOMs).
A DMM (digital multi meter) has autoranging. It goes crazy on a 540H inductor.
Solution for both VOM and DMM:
Short one winding.
Read the second winding DCR.
Short the second winding.
Read the first winding DCR.
Measurement Science At Work.
Do you mean a VOM that has an analog meter movement?
Usually those work to measure DCR of an inductor (as long as they are not auto-ranging).
But you have to wait until the meter overcomes the inductive reactance of 540H (that is a long time constant for most VOMs).
A DMM (digital multi meter) has autoranging. It goes crazy on a 540H inductor.
Solution for both VOM and DMM:
Short one winding.
Read the second winding DCR.
Short the second winding.
Read the first winding DCR.
Measurement Science At Work.
Handheld digital multimeters are inappropriate to measure high inductive coils, even measuring "resistance".
The good old Ohm law is the solution:
3.3V -> choke -> 1mA ampmeter.
The good old Ohm law is the solution:
3.3V -> choke -> 1mA ampmeter.
An excellent idea
Actually, both meters are digital. One measures inductance, capacitance and resistance. No readings for inductance and no readings for resistance. The other has a continuity setting and sets off the buzzer on both chokes🙂 No resistance readings they just wander around. So at least it seems I have not ruined them😱
Actually, both meters are digital. One measures inductance, capacitance and resistance. No readings for inductance and no readings for resistance. The other has a continuity setting and sets off the buzzer on both chokes🙂 No resistance readings they just wander around. So at least it seems I have not ruined them😱
I used to have that problem, until I discovered what to do:
Short one winding, and read the other with the Ohmmeter function.
Then switch which winding is shorted, and which winding is being measured.
Works for me.
Lundahl
Hammond
Fisher
Edcor
Interstage transformers
Output transformers
Power Transformers
Chokes are more difficult. Set the DMM Ohmmeter Range to Fixed Range (a range that includes the estimated or predicted DCR).
Short one winding, and read the other with the Ohmmeter function.
Then switch which winding is shorted, and which winding is being measured.
Works for me.
Lundahl
Hammond
Fisher
Edcor
Interstage transformers
Output transformers
Power Transformers
Chokes are more difficult. Set the DMM Ohmmeter Range to Fixed Range (a range that includes the estimated or predicted DCR).
vetmedrobert,
Perhaps you connected the two windings in series, but did so in Anti-Phase.
That would short out the AC signal to the next grid.
How about that?
Perhaps you connected the two windings in series, but did so in Anti-Phase.
That would short out the AC signal to the next grid.
How about that?
This is a center-tapped coil. I would recommend to connect a 9V battery + pole to each pin 1, 5, 8. The - pole should go to your multimeter common. Check if the voltage appears on the other pins, with the multimeter in 20V setting. This method will not do harm to the choke, because the DMM has 10Mohm input impedance.
Direct resistance measurement is not a good method, because the DMM would try to send some test current through the DUT, and measure the voltage drop. But as soon as you apply a current on the choke, a high induced voltage will appear on it that confuses the DMM.
Direct resistance measurement is not a good method, because the DMM would try to send some test current through the DUT, and measure the voltage drop. But as soon as you apply a current on the choke, a high induced voltage will appear on it that confuses the DMM.
Attachments
An excellent idea
Worked perfectly, I am very pleased with your test😀 Although I perhaps should not try tests like this before morning coffee, both meters were next to each other and I could not get a reading until I realized that I had connected the battery negative to the negative probe of the dmm not turned on😱 Really appreciate your help🙂
Worked perfectly, I am very pleased with your test😀 Although I perhaps should not try tests like this before morning coffee, both meters were next to each other and I could not get a reading until I realized that I had connected the battery negative to the negative probe of the dmm not turned on😱 Really appreciate your help🙂
What's the driver tube in your amp? 540H isn't exactly a ton of inductance for a grid choke, and seeing that you have such a high grid leak resistor makes me wonder...
2C22/7193
Using a ccs and SiC bias. I am amenable to changing that but total current draw already is close to the transformer maximum🙂
Using a ccs and SiC bias. I am amenable to changing that but total current draw already is close to the transformer maximum🙂
2C22/7193
2c22 and 7193 are the driver tubes. Basically similar to 1/2 a 6sn7 or a 6j5, with 2 top caps🙂
7Kohm resistance
2c22 and 7193 are the driver tubes. Basically similar to 1/2 a 6sn7 or a 6j5, with 2 top caps🙂
7Kohm resistance
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