Steve-
I think W8JI indeed does offer plate chokes for sale.
The best way to contact him seems to be on the Facebook
Ameritron amps user group. He says that he goes for many days
without checking his CTR Engineering email.
73
Tom K0SN
On Wed, Aug 24, 2022 at 7:15 PM gudguyham--- via Amps <amps@contesting.com>
wrote:
> Tom W8JI took over Command Tech. He may have a plate choke. Doesn’t hurt
> to email him and see. He’s looking for an L2 toroid for me. Says he does
> have some parts.
>
>
> Sent from the all new AOL app for iOS
>
>
> On Wednesday, August 24, 2022, 9:08 PM, Steve London <n2icarrl@gmail.com>
> wrote:
>
> It's a Command Technologies, HF-2500M.
> The way they have the 3CPX800's mounted, there isn't room for the RFParts
> choke without some modifications
> 73,Steve, N2IC
>
> On Wed, Aug 24, 2022 at 7:04 PM gudguyham@aol.com <gudguyham@aol.com>
> wrote:
>
> Wow, I’ve seen my share of these amps but never saw that happen to a plate
> choke. I’m just thinking. I think I wrongly assumed tnis was a Command
> Tech 2500 but apparently is a QRO Tech 2500. Guys, please, when you ask
> about HF2500’s mention if it’s a Command or a QRO Technology. Thanks
>
>
> Sent from the all new AOL app for iOS
>
>
> On Wednesday, August 24, 2022, 8:35 PM, Steve London <n2icarrl@gmail.com>
> wrote:
>
> Well, it looks like it really is the plate choke. It became obvious with
> the last test.
> See https://www.kkn.net/~n2ic/melted_choke.jpg
>
> Where do I get a new plate choke, or at least a new delrin form to wind my
> own ?
>
> Previously, I looked at currently manufactured 3CX800 amps and their plate
> chokes are too large to fit. I may go back to that idea and see what I can
> do.
>
> 73,
> Steve, N2IC
>
>
> On Wed, Aug 24, 2022 at 6:24 PM gudguyham@aol.com <gudguyham@aol.com>
> wrote:
>
> > Steve, most of the problems with the tank circuit is from having the
> > 40-160m L2 toroid burning up. I’ve got an HF2500 in my shop right now
> with
> > a melted down L2 toroid. There is a VERY NARROW group of possibilities
> > that can be causing your problem. You’ve done some good detective work so
> > far and it seems you’ve covered some good possibilities. You said you
> > checked the connections to the band switch and to the coil. Obviously if
> > the tap going from bandswitch to L1 is bad on either side you would be
> > loosing the tank circuit. But you checked that already and I assume
> > accurately. So if your troubleshooting is accurate I can only think of
> one
> > last thing that could be wrong.
> > CHECK THE PLATES ON THE LOAD CAP!! The arcing you heard may have
> bubbled
> > a plate or plates on the load cap and when the load cap is in the
> resonant
> > area for 15 meters the rotor plate may be shorting to the stator plate.
> > Use a high power flashlight and inspect the load and tune caps for any
> > interference throughout the rotation of the plates when in the 15 meter
> > range. I assume you checked the plate choke already and I also assume
> you
> > are using a dummy load to rule out an antenna problem. Lou
> >
> >
> > Sent from the all new AOL app for iOS
> > <https://apps.apple.com/us/app/aol-news-email-weather-video/id646100661>
> >
> > On Wednesday, August 24, 2022, 6:51 PM, Steve London <n2icarrl@gmail.com
> >
> > wrote:
> >
> > I have a HF2500 with a pair of 3CPX800's. It's been a great amp.
> >
> > Up until now, it's had a minor issue. The tuning/loading drifts of 15
> > meters as it heats up. Not a big deal - just a small tweak of the tuning
> > brings it back to full power. No issue with any other band.
> >
> > Today, while operating, it went dead on 15. Suddenly, only a few watts
> > output. No drama, bangs, etc. 30 mA grid current, 750 mA plate current.
> > Tweaking the tuning made no difference, until it was way out of normal,
> > when it increased to 250 watts and something arc'd. All other bands are
> > fine.
> >
> > Here's what I did, so far:
> > - Examined the band switch and contact to the 15 meter tap on the coil.
> > Looked good and measured good with an ohm meter.
> > - Examined the tuned input network. No obvious problem. Placed a 47 ohm
> > resistor across the output of the input network, instead of the tubes.
> SWR
> > and Z looked nominal on all bands.
> > - Bypassed the input network, driving the tubes directly. Still bad on 15
> > meters. All other bands are good.
> >
> > So, that eliminates the input network as the problem.
> >
> > What am I missing on the PA or Pi-L side that would only affect 15
> meters ?
> >
> > 73,
> > Steve, N2IC
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
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