Which is why I dont recommend it unless you insulate it.
Check with QRO, Ten-Tec and also see if Palstar has any left. The Ameritron
is 1" diameter, you need 3/4" or less.
Carl
KM1H
----- Original Message -----
From: "Bob K6UJ" <k6uj@pacbell.net>
To: "Amps@contesting.com" <amps@contesting.com>
Sent: Wednesday, April 11, 2012 10:13 AM
Subject: Re: [Amps] Plate choke help.
> Hi Carl,
>
> I'm worried now about trying the RFC-3 in my 76CA. Rick says "it is much
> bigger" .
>
>
> Bob
> K6UJ
>
>
>
> On Apr 11, 2012, at 6:51 AM, Carl wrote:
>
>> RFC-3 IS the Ameritron choke which is $20 direct.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message ----- From: "Bob K6UJ" <k6uj@pacbell.net>
>> To: "Amps@contesting.com" <amps@contesting.com>
>> Sent: Wednesday, April 11, 2012 12:34 AM
>> Subject: Re: [Amps] Plate choke help.
>>
>>
>>> Rick,
>>>
>>> I also have an Alpha 76. My plate choke looks like it got hot down
>>> close to the bottom which I think is the high voltage end. I want to
>>> replace mine too.
>>> According to KK5DR in his webpage on the 76
>>> http://www.kk5dr.com/OLD76.pdf he says that RF Parts No. RFC-3 is a
>>> replacement. I am ordering one of these and see
>>> how it works out. It sells for $25.00 so pretty easy on the wallet,
>>> hihi. On the caps, I would think the Alpha cap values would be the ones
>>> to use for the coupling and bypass, but I'm no expert, hopefully one of
>>> the amp gurus can shed some light on it.
>>>
>>> Bob
>>> K6UJ
>>>
>>>
>>>
>>> On Apr 10, 2012, at 5:48 PM, rick darwicki wrote:
>>>
>>>> Hi all,
>>>>
>>>> I replaced the plate choke in an Alpha 76 with an Ameritron that is
>>>> much bigger. First time out it arced to the nut on the back of the load
>>>> cap. This is an older 76 with the long cap so there isn't much room.
>>>>
>>>> I replaced the choke and put a piece of glass between it and the RFC
>>>> and a 1/4" thick pice of plexiglass between the blower and the RFC.
>>>> Well apparently the the Plexiglass lowered the resonate freq enough
>>>> that it acred over to the blower on 20 M. I removed the plexiglass and
>>>> put some corona dope on the choke and all seems well. I can tune to
>>>> full power with 100 ma grid drive on all bands.
>>>>
>>>> The interesting thing is on 160/24/28 at 100 ma grid current I am
>>>> showing about 900 ma plate current at max forward power, 1:1 SWR. On
>>>> the other bands max power at 100 ma grid current is at about 600 ma
>>>> plate current. It seems like there is a lot of RF on the key on 17 M
>>>> but the cover is off.
>>>>
>>>> What I am wondering is if I should use the same coupling cap and RFC
>>>> bypass as Ameritron uses in the AL-80B with their choke. They use
>>>> 0.002 coupling and 0.001 bypass.
>>>>
>>>> I kept what was in the Alpha for RFC bypass and installed a big Russian
>>>> 0.002 coupling cap.
>>>> At the bottom of the choke is a 0.006 (three 0.002's) to ground, a 15uh
>>>> series choke and a 0.008 (four .002s) to ground that go to B+.
>>>>
>>>> The original Alpha arrangement was 0.004 coupling, 0.004 bypass, 15uh
>>>> series, 0.004 bypass.
>>>>
>>>> I don't know what the best thing to do is. I wondering if the 15uh is
>>>> necessary or screwing up the Ameritron.
>>>>
>>>> Any comment will be greatly appreiciated.
>>>>
>>>> Thanks,
>>>>
>>>> Rick N6PE
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Rick, N6PE
>>>> ==================================
>>>> Talk is cheap... except when Congress does it.
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
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