Official Safety Announcement from the AMATEUR RADIO SAFETY COUNCIL
Since there have been a rash of Ham Operators changing their final tubes
with the amplifiers running and making power recently we highly recommend
seeking a highly trained technician to perform the tasks at hand if you
don't feel up to the complex nature of these procedures.
If you cannot or will not heed this warning we highly recommend this
procedure:
Please turn the amplifier power switch off and remove the line cord from the
wall before removing the covers. (Blown .82 ohm resistors in L4-B's prove
this isn't necessarily the case.)
Before reaching in and grabbing on to something inside the chassis, use a
shorting wand to make sure all voltage is removed from the supplies. On
tetrode amps, you might want to short the screen supply and don't forget
those pesky 12 and 26V relay supplies as they've been known to blow off
limbs if you come in contact with them.
It is highly recommended to look around and visualize the configuration of
leads and interlocks of your amplifier. This will assist you in
reconnecting HV leads and flipping interlocks to their proper places.
Finally before grabbing your bottles, make sure the GLOW ON THE PLATES has
subdued from a bright Orange Color to at least a dull red or darker to avoid
burns which may or may not require skin grafts.
Once the change out has been accomplished, please return all HV leads to
their proper places and replace covers to avoid interlock and shorting bars
from doing additional damage to the amplifier while attempting to do their
job. Which BTW is generating factory service of the amplifier after severe
damage occurs from shorted HV interlocks. The problem is this amplifier has
outlived the factory itself and all qualified factory service personnel.
Replace line cord to outlet and use a pencil or other pointy object to flip
the main power switch on while cringing and leaning as far from the
amplifier as possible.
We here at the AMATEUR RADIO SAFETY COUNCIL hope you will have a safe and
powerful day.
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Paul M Dunphy
Sent: Friday, April 20, 2007 4:41 AM
To: Amplifier- List
Subject: [Amps] ACOM-1000 replacing tubes
I've pretty much talked myself into getting an ACOM-1000. Even
with the prices of the 4CX800As increasing, I'm still impressed with
this amp. The one reservation is that the manual says, "Replacement
is a complex and potentially dangerous operation. For this reason we
recommend this work be carried out by a trained service technician."
How "complex" is this? I've been changing tubes in older amps
like Clipperton-Ls, TenTec Centurions and AL-811Fs for years. I have
friends who routinely have replaced 8877s in AL-1500s, 4CX800as QRO
Technologies, etc.
I don't want something so complex that I have to send it back to
the supplier to change a tube! It's too bad the manual was a bit
more specific on what is involved. Has anyone changed one, or know
what they are referring to in terms of it being complex or
dangerous? I don't expect to have to do this often (probably once
every 5-10 years), but tubes are tubes in any amp, and eventually
they wear our. I'm not an Electrical Engineer, but I'm pretty good
at electronics and I've been playing with amps and the like for 20+
years. I can't imagine it is that bad.
Thanks!
73, Paul VE1DX
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