[Boatanchors] tube tester readings

[WA5CAB at cs.com]

I think that the regular settings on charts or rolls on tube testers with a 
GOOD/BAD scale are usually intended to cause a reading relative to the 
GOOD/BAD markings, not the numbers.  If you think about it, you'll see that must 
be the case.  Else if the Discard line happened to be at 50 on the numeric 
scale, and the multiplier at 100 whether so marked or not, any tube with 
less than 5000 uMhos would be rejected.  There go most triodes.  :-)  Or if the 
multiplier was at ten, almost any pentode without shorts or an open 
filament would pass.  On a tube tester with both a GOOD/BAD scale and a numeric 
scale, there should be somewhere in the TM instructions on how to set it to 
read uMhos directly instead of GOOD/BAD.

In a message dated 2/23/2010 4:54:47 PM Central Standard Time, 
jfor at quik.com writes: 
> Not SPECIFICALLY about your unit, but about Transconductance in general:
> 
> ==========
> 
> Transcoinductance is:
> 
> Change in Plate Current / Change in Grid Voltage
> 
> The units of measure are reciprocal Ohms (1/Ohms) also called Mhos
> 
> If the Plate Current is in mA and the Grid Voltage in Volts the numbers
> are inconvenient so uM is used (MicroMhos)
> 
> Example: If Ip change = 5 mA ; for a Vg change of 1 V:
> 
> Ch. Ip / Ch. Vg = 0.005/1 Mhos or 5000 uMhos.
> 
> If you look at your meter multiplier, there is likely x100 position, so
> 5000 uM would read 50 on your scale of 0 to 120.
> 
> Best,
> -John
> 
> ===================
> 
> >Ok, this may seem like a duh to some, but on my B&K Dyna-jet tube
> >tester, the meter is scaled numerically from 1-120 but I have no idea
> >what the reference quantity means. The REPLACE-REJECT-GOOD markings
> >are not too much for my small brain. I know this is a mutual
> >conductance tester and I know what that means but have no idea how
> >this scale translates to that.
> >
> >Another unknown is regarding dual section tubes. The chart shows a
> >test 1 and test 2 but no reference in the manual as to which section
> >of the tube is which.
> >
> >Please enlighten me.
> >
> >Thanks and 73, Dick KF4NS
> >St Petersburg, FL 33714 USA
> >Keep The Glow!
> 

Robert & Susan Downs - Houston
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MVPA 9480