[Amps] Dual 3-1000Z amp problem

[Clark Turner]

Thank you for the reply. We found that I had used the wrong value plate 
load impedance when making my tuning chart.  Once the network was tuned 
for 3K ohms, things started to work as they should.  The amp will run 
3000 or more out with a 100 watt radio now with the tuned input. The 
only trouble I am having now is the weak RF parts Plate choke. Its 
starting to unwind on my again when running on 15 meters. We are going 
to have to wind a new 2.5 to 3 amp rated choke and install it. The issue 
is that the PS is a 3 amp PWD transformer and if you get an oscillation, 
glitch or mistune the amp even for a second, the 1.5 amp rated choke is 
the weak link and it goes. This is my second one and its already showing 
some hot spots.

C

On 4/20/2016 8:04 AM, Jim Thomson wrote:
> Date: Mon, 18 Apr 2016 19:19:35 -0700
> From: Clark Turner <Clark at ClarkTurnerTuning.com>
> To: amps at contesting.com
> Subject: [Amps] Dual 3-1000Z amp problem
>
> I just finished my Dual 3-1000Z GG amplifier.  I have an odd issue now
> that I cant seem to figure out. The amp will do 2KW with 40 watts of
> drive on 80 meters.  Additional drive does not add any power out.  100
> watts input does 2kW out.  The Input SWR is low at 1.2 to 1.  The plate
> current DOES increase, But there is no additional output.
>
> I had this amp running before with 4-1000 and 3-1000s and some of you
> remember, I turned the roller inductor on accident when I was trying to
> reach for the load turns counter. That toasted the plate choke. I
> replaced that choke and while I was in the amp, I installed RF parts
> RFC30 chokes instead of the HB ones.  I was having high input on 80 so I
> changed them out. That is fixed but I now have this new issue.
>
> Any idea where to go?  This condition exists on 40 and 80.  2KW easy.
> But then it wont make more.
>
> ## what wattemter are u using ?   what is the ant, or is this a dummy load ?
> If plate current rises, and no increase in PO, ur PD  would be sky high.
> Does ur grid current also rise ?   Is either the tune or load cap maxed out
> on 80 or 40m?   Is it a PI or PI-L  on 80 + 40M ?   U sure u have the
> tank coil taps in the correct place?
>
> ##  a 3-1000Z is rated for  6 kv.   You should be able to make stupid power
> on any band.
>
> ##  OK, so the issue is only on 80+40m.  But its good on all other bands.
> How much does it put out on the other bands ??
>
> ##  I have seen a few cases of bad slugs on bird wattmeters, but that is rare.
>
> Jim   VE7RF
>
>
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