I put a 240 to 120 transformer (to run the filament transformer and the
blower) in my HB 3CX800 amp because the Dahl plate transformer only had
a 240 volt primary winding.
The transformer was about $30.00 from Mouser.
Works perfectly!
Thanks
73
Jim W7RY
On 5/7/2021 12:32 PM, Jim Thomson wrote:
Date: Fri, 7 May 2021 09:34:25 +1000
From: Adrian <vk4tux@gmail.com>
To: 'Amps group' <amps@contesting.com>
Subject: Re: [Amps] Alpha 87A Power Supply Question
<It is dangerous, additional to my earlier post connecting neutral to
<chassis and wiring 120v returns to same terminal, if the neutral
<connection opens anywhere from within the amp back to the supply, then
<you have 120v on the amp chassis at turn on, waiting for you to grab.
<Usually, it takes about 30 mA of current to cause respiratory paralysis.
<Currents greater than 75 mA cause ventricular fibrillation (very rapid,
<ineffective heartbeat).
<vk4tux
## On a related note, IF a sub panel is used, like in my case, I installed a
100 amp sub panel on the other side of the wall of the basement shack, with
short runs
through the wall to the 4 x amps, 4 x xcvrs etc, etc. In the case of a sub
panel, the neutral
and ground can NOT be bonded together. Reason is, if a fault occurs, ALL
the fault current has
to return to the main 200 amp panel via the ground wire...straight through
to the main 200 amp panel.
## IF the neutral and ground are bonded together in a sub panel, the fault
current from the equipment in
the shack will initially return through the ground wire back to the SUB panel,
then the fault current will split,
with 30-40 % going back to main 200 amp panel via the grnd wire....and the
remaining 60-70% returning via the
neutral wire. Grnd wire these days is typ smaller gauge than the neutral,
hence the offset split in current.
Any fault current returning via the neutral is a big no-no. The ONLY place
the neutral + grnd is bonded is in
the main 200 amp panel.
## my drake R4C and T4XC came with 2 prong plugs, no grnd. Drake installed
.01 uf disc caps, between hot and
chassis.......and also between neutral and chassis. That puts 120 vac
across the 2 x caps..that are effectively
in series.... via the chassis. That’s 60 vac per cap. You end up with 60
vac on the chassis. I got zapped one day, when
disconnecting coax, etc. I measured 60 vac between the chassis of the
drake..and the cold water tap ! Easy fix, replace
the 2 wire cord, with a 3 wire cord, and use proper X-Y AC rated
caps..instead of .01 uf at 1 kv rated disc caps.
## on my 4 x drake L4B amps, I replaced the oem fubar 120 vac blower with
the 230 vac EBM papst blower, as used in the AL-1200,
AL-1500, AL-82 amps. For some reason, the 230 vac version of that EBM
blower is almost half the price of the 120 vac version.
Mouser and digikey sells the 230 vac version for aprx $112.00 The 115 vac
version is almost $200.00 from mouser + DK. The 115 vac
version used to be $137.00 from MFJ, but price has now gone up to $168.00
But this precludes running the amp on low power, on 120 vac..which I have never
done anyway. Drake had used the quasi neutral scheme
to obtain 120 vac for the oem 120 vac blower. For 115 vac operation, I
could use a 115 to 230 vac small xfmr to run the 230 vac blower.
## On a lot of commercial henry amps, they used a 240 to 120 vac small
xfmr to run the 120 vac blower.
## I have never seen the 3 wire, 2 hots + grnd wired in any home here in
BC. Its been 4 wire at least since 1960, or earlier.
I assume the USA 3 wire fubar scheme was to save 1 wire...and some money.
Seems silly, since copper was dirt cheap way back then.
Jim VE7RF
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