6146 Replacement

[W5EUQ]

Okay guys.  Question.  Tell me again WHY to not use a 6146B in a DX-40?  
Maybe I'm a slow learner on this subject....   HI.

I know the 6146B's are not as good as the 6146A's, for example.  I also 
understand they are built somewhat different to the A model.... and may 
be the characteristics are different.....

 however, I have put two 6146B's in my DX40's(actually both DX40's came 
with B's in them)  and I get almost 50 watts output... So I put some 
6146A's in both rigs and got the same power, same everything.......  so 
do the B's self destruct, not last as long, oscillate or what?    
Neutralization changes so that it oscillates? 

So tell me one more time...but please tell me what is fact, not what is 
"wives tales"....   I promise to pay attention this time...   Bob

Bill Coleman wrote:
> On Aug 29, 2006, at 2:26 PM, Davies, Doug A FOR:EX wrote:
>
>> Well, I've digested all of the replies on this query and I think I'm
>> going to try one of the 6146B's in the DX-40.
>
> The DX-40 was designed for the 6146/6146A. I would not use the 6146B 
> in it.
>
>> This rig doesn't require
>> any neutralization in the true sense of the word so I'm going to give it
>> a shot.  If the output continues to drop off, I obviously have other
>> problems.
>
> First thing to check is the plate supply voltage under load. It needs 
> to stay around 600 volts in order to get the required output. Also 
> check the screen supply and resistor. If the resistor has drifted to a 
> higher value, it may cause the current to fall off.
>
> Another thing to be wary of is bad metering circuits. The resistors in 
> the metering shunt may have changed value over time. The tube could be 
> operating normally, but the meter lies.
>
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
> Quote: "Not within a thousand years will man ever fly!"
>             -- Wilbur Wright, 1901
>
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