This has always been a concern of mine and in fact an older Alpha PA-70V I
restored suffered from this: At one point during the restoration process,
the +28 VDC supply failed upon start-up. Since this inhibited the
step-start process (K2 contact closure), both 10-ohm/25-watt step-start
resistors quickly failed and left a Helluva mess afterwards. I had cuts all
over my hands from the glass/vitreous enamel shrapnel during the clean-up
effort.
My current PA-70V was designed prior to the factory integration of the "F3"
step-start fuse. I'm assuming that F3 is placed in series with one of the
two 10-ohm @ 25-watt resistors? In factory units, is this fuse panel
mounted or simply installed as a "pigtail" fuse holder on the step-start
frame? Also, what is the fuse rating? I would think it's a slow-blow
device? Thanks!
-Paul, W9AC
----- Original Message -----
From: "Phil Clements" <philk5pc@tyler.net>
To: "NOLL AMIDZICH" <NAMIDZICH@wi.rr.com>; <amps@contesting.com>
Sent: Tuesday, June 12, 2001 9:56 AM
Subject: Re: [AMPS] SICK ALPHA 77DX
>
> This is a common problem in old Alphas.
> F3 is a protection fuse in case the step-start
> relay fails to close in its allotted time.
>
> Check K2 and R2 for failure/burning
>
> GL!
> Phil, K5PC
>
>
> Subject: [AMPS] SICK ALPHA 77DX
>
>
> >
> > Hello to all,
> >
> > I have an Alpha 77dx that had been working fine until yesterday.
> >
> > Now when I turn on the amp there is no high voltage. (There is about 230
> > volts per the Alpha meter). The blower runs but the amp will not switch
> > into the "standby mode". I checked the fuses and the 2 amp "F3" fuse
had
> > blown. I replaced this fuse with another 2 amp "slow blow" fuse.
Powering up
> > the amp again resulted in another blown fuse after about 3 seconds.
> >
> > Any advice would be appreciated.
> >
> > Thanks
> >
> > Noll W9RN
> >
> >
> > --
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> > Problems: owner-amps@contesting.com
> >
> >
>
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
>
--
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