Ameritron, MFJ will sell parts.
Sent from my iPhone
> On Aug 26, 2022, at 20:07, Tom Hellem <tom.hellem@gmail.com> wrote:
>
> 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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