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Author Topic: TL922 Grid Current  (Read 18314 times)
W8JI
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« Reply #45 on: March 11, 2014, 05:17:10 AM »

That is an oddball meter KW uses. What meter did Doug use?
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W1QJ
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« Reply #46 on: March 11, 2014, 01:33:41 PM »

That is an oddball meter KW uses. What meter did Doug use?

Tom, I have no idea what meter Doug has there.  I have to assume it is not a 500ua meter.  If he measures the pot and lets us know what the resistance is that worked we can figure it.  My guess is he needed less than the 366 ohms we calculated.  Tom. obviously when you clone a meter you are looking for a meter that looks like the original so that it fits and can not be identified as a clone.  The originals are not available.  So in that case you get the meter that fits the bill and work around it.
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W8JI
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« Reply #47 on: March 11, 2014, 01:39:33 PM »

That is an oddball meter KW uses. What meter did Doug use?

Tom, I have no idea what meter Doug has there.  I have to assume it is not a 500ua meter.  If he measures the pot and lets us know what the resistance is that worked we can figure it.  My guess is he needed less than the 366 ohms we calculated.  Tom. obviously when you clone a meter you are looking for a meter that looks like the original so that it fits and can not be identified as a clone.  The originals are not available.  So in that case you get the meter that fits the bill and work around it.

He said it read real close on HV. Assuming he did not change resistors in the multiplier resistors, it has to be 500 uA.

If he changed multiplier resistors all bets are off, but since he never said anything about replacing multiplier resistors I assume it was 500 uA.

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W1QJ
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« Reply #48 on: March 11, 2014, 02:48:40 PM »

Tom, apparently he did not install the meter.  he got it that way.  Since the calculated resistor did not work it can't be 500ua so I assume whomever did install the meter mus have changed the HV metering resistors.  It doesn't seem like Doug knows much about the history of the amp.  But it appears that the resistance was lower than the calculated 366 ohms which was based on a 500ua meter.  So i has to be different and according, a higher current.
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K6JEY
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« Reply #49 on: March 15, 2014, 11:49:41 AM »

Hi All,
   Final results.
     I put my clamp on DC ammeter on the lead from the bias diode and measured the combination of plate and grid current. I noted the plate current (the amp was tuned up to 400 watts output at the time) I subtracted the plate current from the total and set the series pot in the meter line to read the grid current. That having been done, the amp acts and looks normal. The grid current swings as it should with increasing drive and indicates appropriately given other parameters.
     Problem solved. Many thanks to all who participated and gave advise.
    Doug K6JEY
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W8JI
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« Reply #50 on: March 16, 2014, 01:45:21 AM »

Where did you get the meter rebuilt, and what movement was used?
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W1QJ
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« Reply #51 on: March 16, 2014, 03:34:46 AM »

Tom, he got the meter with the amp when he obtained the amp.  he had nothing to do with the meter.  He got i he way i was. I assume it must have been one of the meters that Myself and Gordon cooked up.  It was meant to be an Ip replacement meter not a multimeter replacement.  Of course what he had might have been something totally different.  I am just guessing and he does not know.
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