Gerald, see an eye doctor!
>From his original post:
>> So I replaced the Resistors, This Time with 75K OHM Flame proof
>> Resistors,
>> all Eight of them with the same wattage and replaced all Eight
>> Electrolotyic Capacitors, all I had were 220MFD at 450VDC
However if the replacement caps were those little imports its no wonder they
failed.
Carl
KM1H
----- Original Message -----
From: <TexasRF@aol.com>
To: <n9bx@mchsi.com>; <Amps@contesting.com>
Sent: Tuesday, October 30, 2007 3:45 PM
Subject: Re: [Amps] Ameritron AL-1200
>
> Sounds like eight new capacitors and eight new bleeder resistors would
> take
> care of the immediate problem. After multiple failures there is a
> likelihood
> that the remaining capacitors have been stressed enough that their days
> are
> numbered.
>
> 73,
> Gerald K5GW
>
>
> In a message dated 10/30/2007 1:00:43 P.M. Central Daylight Time,
> km1h@jeremy.mv.com writes:
>
> There are those who would have you believe that Ameritron used a special
> capacitor not available to us common folk. I have no idea if it is true
> but
> I suggest that you call Ameritron and dont rest until you are put in
> touch
> with someone who is in the position to answer.
>
> Carl
> KM1H
>
>
>
> ----- Original Message -----
> From: <n9bx@mchsi.com>
> To: <Amps@contesting.com>
> Sent: Tuesday, October 30, 2007 1:03 PM
> Subject: [Amps] Ameritron AL-1200
>
>
>> Hi: I have a perculiar problem with the high voltage power supply on
>> the
>> AL-1200. Here is the sequence of events.
>>
>> I had the Amplifier on and it was idling and all of a sudden it
>> crackled,
>> stopped and about 15 minutes later did this again. High Voltage stayed
>> the same ,(meter Indicates 3600-3700 VDC, The whole time. Well I shut
>> it
>> down and after the HV was alowed to bleed off I started checking the
>> filter cpacitors. this amp used 210 MFD at 450 VDC and Had eight of
>> them.
>
>> Yes I know that 8X450 =3600 Volts, and that's about what my voltage
>> reads
>> on the meter but I figured the designers of this Amp knew what they were
>> doing and there was an adequate safety margin built in.
>>
>> Well One of the Capacitors was Bad. In fact the little white Dot that
>> is
>> on the Capacitor was bubled up and the Capacitor did not charge or
>> discharge. I then checked all of the 50K ohms 7 watt resistors across
>> the
>> Caps and sure enough two of them read open. These were the ones that
>> were
>> across this Cap and the one Adjesent to it.
>>
>> So I replaced the Resistors, This Time with 75K OHM Flame proof
>> Resistors,
>> all Eight of them with the same wattage and replaced all Eight
>> Electrolotyic Capacitors, all I had were 220MFD at 450VDC so Hey A
>> little
>> bit more voltage regulation key down but not that much.
>>
>> Turned the unit back on Everything was fine. Made one QSO, Voltage was
>> above 3600 VDC again as before and I thought the Amp was back in
>> Business.
>> Well after sitting with no load on it two hours it started crackling
>> Again, and one again it does this at about the 15 minute interval.
>>
>> I am almost sure that I will find the same Bad components agin, but What
>> is causing the Capacitors, Or more likely the equalizing resistors to
>> fail
>> which causes the Caps to Fail.
>>
>> Sorry for the Bandwidth but this amp has been in service for 12 Years
>> with
>> not a hint of Problems before This Started to Happen.
>>
>> 73 Bruce N9BX
>> _______________________________________________
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>>
>
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