From: Garey Barrell 
Subject: Re: [drakelist] T-4XB apparent vs actual plate current


Hi Al -

That works.   Four measurements and two calculations..  :-) 
   I used to lift the lead from the cathode feedthrough and 
insert a meter.   Then I got "uptown" and now use an HP 
Clip-on Hall-effect meter on that lead.

Several more than one way to skin the proverbial ...

73, Garey - K4OAH

Al Parker wrote:

> Hi Don,
>     If you measure the final cathode resistors (accurately), and measure
> the voltage directly across them when at idle, you can calculate the
> actual final current probably more accurately than  the way you've done it
> (remember, they don't go directly to gnd).  That's the way I do it when
> ckg/fixing meter accuracy.  I thought you had mentioned earlier that you
> had ckd the screen & cathode resistors, replaced the screens', but I can't
> find that msg now.
> 73,
> Al, W8UT
> New Bern, NC
> BoatAnchors appreciated here
> http://www.thecompendium.net/radio/
> http://www.hammarlund.info
> 
> 
> ----- Original Message ----- 
> From: 
> To: 
> Sent: Wednesday, March 03, 2004 12:47 PM
> Subject: [drakelist] T-4XB apparent vs actual plate current
> 
> 
> 
>>OK, Garey-I checked the meter, and it showed .16 volts thru the
> 
> connections on the back of the housing.  The shunt resistor measures 3.1
> ohms in circuit, and 3.3 ohms out.  Using the 3.1 ohm figure, that would
> make the actual current around 52 mA.  This is with the pot on the back of
> the AC-4 set to read an apparent 70 mA on the meter.  Assuming my cheapie
> DMM is anywhere near accurate, I am seeing a significantly higher
> appparent vs actual plate idle current reading.  I looked through the
> T-4XB manual, and did not find anything specific as to meter calibration.
> What is the usual cure for this situation?
> 
>>On the bright side, the AC ripple in the transmit signal is now gone
> 
> with the replacement of the old C4 cap in the AC-4 PS.
> 
>>73,
>>
>>Don, W5EI
>>Troup, TX

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