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
> _______________________________________________
> 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
|