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Subject: [AMPS] 4-1000 IDLING CURRENT
From: (Rich Measures)
Date: Sun, 29 Mar 98 00:39:55 -0800
>My Home brew 4-1000 amplifier works great except for on thing.  The power out
>seems low.  I believe it may have something to do with the low idling 
>Plate voltage is 4,600 VDC and idling current is about 80 ma.  

Zero signal anode current - a.k.a. idling current - should be about 20% 
of max.., or around 150mA.  

>The max plate
>current I can load it to is 450 - 500 ma.  At 4,200 VDC under load and 450 ma
>plate current, gets 1,450 watts out with about 130 watts drive.  

Normal drive power is around 190w with such low anode V.  If you want to 
make an 8166/4-1000A play well with low drive levels, you need 6 to 7kV 
on the anode.   

>Have checked
>the B- line for stray resistance; none.  Have tried it with the zener both in
>and out; no difference.  

If the zener in and out makes no difference, the zener may be shorted.  

>Power supply is capable of more than enough current
>and I have 200 watts available.  I have 3 tubes: all 3 operate the same in my
>amplifier, full output in another amp.
>Any suggestions!
If you want to realize the full capability of the 8166, you need to drive 
it to about 750mA, Bob.  Grid-driven, 100w will do it, however, in 
grounded-grid, it takes about double that.  
- later


R. L. Measures, 805-386-3734, AG6K   

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