Yeah likewise,
About a year ago when I was just getting started on Amp gear, I was
doing
some tube tests. I was going through a routine of powering down, replacing
the 4 PA tubes, powering up again to test the tubes, then powering down
again for the next set of tubes etc. After a while, I got out of sync. and
I was just putting my hand into the PA compartment to remove the anode
clips when I barely noticed a very faint purple-ish glow through the tube's
ceramic insulator. Fortunately this registered somewhere in the deep
recesses of my brain suggesting that perhaps this wasn't a good time to
proceed! Sure enough the HV was still on. It was only 2KV and not 6KV like
yours Jon, but I still shudder when I think how close I came. If it hadn't
been dark enough in the tube compartment to see the faint glow
.................. ?
The manufacturer's maintenance manual points out that that interlocks
were
not deemed necessary because they had plastered the chassis with adequate
high voltage warning stickers!!
I now try to keep the habit of always shorting out the anodes before
going
in, regardless of the powered status of the amp, even at the risk of
possibly damaging something if the HV is on. At least I will stay undamaged
:-)
I recall that thirty years ago when I worked at Collins Radio here in
Oz,
building 208U-10 10Kw SSB transmitters, it was a sackable offence for the
test technician to work in the PA compartment without first applying the
built-in shorting wand to the HV supply.
Cheers,
Graham (VK3BKG)
----------
> From: Jon Ogden <jono@enteract.com>
> To: Dick Green <dick.green@valley.net>; Michael Tope <W4EF@pacbell.net>;
'AMPS' <amps@contesting.com>
> Subject: Re: [AMPS] Resoldering 3-500Z Filament Pins ??
To: <amps@contesting.com>
> Date: 02 04, 1999 7:51 AM
>
>
> >Semiconductors all over the radio blow before
> >the fuse does.
>
> One of Murphy's Laws of Electronics! The circuit intended to be
> protected BY the fuse will blow first, thereby protecting the fuse!
>
>
> > And let's not talk about the time I touched one of the plate
> >caps on an SB-200 because I thought it was loose and forgot that HV was
on.
>
> Ouch! Makes me think of what I almost did. About a year ago I powered
> up the filaments on my amp as part of some initial smoke tests. I was
> tempted to touch the anode and make sure the tube was well seated in the
> socket. I didn't. When I went to turn the filaments off, I noticed my
> HV meter was not zero. Unbeknowns to me, I had earlier left the HV
> supply switch turned on so when I turned on the filament switch, the HV
> was on as well - at 6 KV! I about fainted and I still get queasy till
> this day thinking of what I almost did.
>
> **** But I followed a rule I set for myself and I lived. And that was
> to NEVER touch the tube when the filaments are on w/o first DOUBLE and
> TRIPLE checking to make sure that the HV is off. I'm grateful I made
> that rule!
>
> 73,
>
> Jon
> KE9NA
>
>
>
--------------------------------------------------------------------------
> Jon Ogden
>
> jono@enteract.com
> www.qsl.net/ke9na
>
> "A life lived in fear is a life half lived."
>
>
> --
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> Submissions: amps@contesting.com
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> Search: http://www.contesting.com/km9p/search.htm
>
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