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
> <https://apps.apple.com/us/app/aol-news-email-weather-video/id646100661>
>
> 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
> >
> >
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|
