Am I just imagining things or does Ameritron always say it's the tube? Seems
like everyone whos called them and posts here says they said it's the tube.
Will
*********** REPLY SEPARATOR ***********
On 3/9/05 at 3:37 PM R.Measures wrote:
>On Mar 9, 2005, at 10:34 AM, Rick Low wrote:
>
>> Filament/cathode to grid short is the answer.
>>
>> Thanks for the info and Ameritron confirms this behavior indicates the
>> 3-500Z is ready to be replaced.
>
>This condx is not the tube's fault. I'm using an Amperex tube that
>was manufactured in 1967, the filament helix is still straight, and it
>still delivers the suds. .
>
>> The other symptom that I had not previously
>> seen until my attention was directed to it---grid current goes negative
>> during this condition.
>>
>> Ciao 73 de Rick I0/N6CY
>>
>> -----Original Message-----
>> From: R. Measures [mailto:r@somis.org]
>> Sent: Tuesday, March 08, 2005 13:02
>> To: Rick and Theresa Low
>> Cc: amps@contesting.com
>> Subject: Re: [Amps] AL-80B unusual plate current behavior
>>
>>
>>
>> On Mar 8, 2005, at 1:34 AM, Rick and Theresa Low wrote:
>>
>>> Several times in the past week I?¥úve observed unusual behavior from
>>> this single 3-500Z amplifier and need to know if this looks like the
>>> tube is about to go belly up on me, or if there is some circuit factor
>>> that?¥ús causing this behavior:
>>>
>>> 1. First turn on, plate current indicates about 200-250 mA without
>>> amplifier going into transmit mode.
>>
>> My guess is a filament to grid short since 250mA on standby sounds like
>> 0v bias and it's normally c. 25v on Standby. I would test the grid-fil
>> BD voltage with a high-pot to find out what's what. .
>>
>>> I turn ON with the standby switch in STBY. Stays this way for about 3
>>> to 5 seconds, then zero current.
>>>
>>> 2. At seemingly random times during T/R operation, plate current meter
>>> shows same 200-250 mA, input circuit shows HI SWR on the driver rig,
>>> and of course, no RF output. Cannot clear by cycling T/R relay---PTT.
>>> I turn off, wait about 10 seconds minimum, then turn on and get the
>>> same ?¥þFirst turn on?¥ÿ behavior above.
>>>
>>> De Rick I0/N6CY Gaeta IT JN61sf
>>>
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>
>> Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>>
>>
>>
>
>Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>
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