----- Original Message -----
From: "Mike Williams" <mj...@bellsouth.net>
To: <drakelist@zerobeat.net>
Sent: Sunday, August 12, 2012 9:19 AM
Subject: Re: [Drakelist] Hum in audio
Carey,
I had the same issue with my T4X; it turned out to be the
AC-4. As Richard mentioned, use a scope or have a ham
with a spectrum scope watch your signal on key down. I
installed the Heathkit shop PS kit since it was long
overdue anyway.
73, Mike W4DL
I suspect this is not the power supply but its always
worth checking it. I have two AC-4s with the Heathkit shop
kit in them. Both work fine. I suspect that just replacing
the caps with some from Hayseed Hamfest would do as well.
The Heathkit shop kit replaces all the caps plus the
rectifiers and resistors but usually its only the caps that
go bad. When I did my AC-4 I removed the unused can caps
from the chassis. I suppose some people leave them on for
cosmetic purposes but I don't see any sense to that plus the
openings in the chassis from the old caps are convenient for
wiring.
Note that there is a fair amount of ripple on the HV
line especially under load. I also found the voltages given
in the Heathkit instructions were optimistic.
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
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