[Amps] Alpha 87A Power Supply Question

Tue May 4 10:24:58 EDT 2021

I believe the appropriate hookup depends on the circuitry. As already
noted, the guiding principle is that return current should always be
through neutral, and never through ground. This is an important safety
consideration.  For example, if your modern 240VAC amplifier uses L1,
L2, N and G, but has a 120VAC blower, the blower should be wired
between L1 and N, not L1 and G.

Older three-wire houses usually have 240V circuits wired for L1,L2,N
(and not L1, L2, G). Unfortunately, older amplifiers (e.g, the L4B and
30S1) often have L1,L2 and G connections, but don’t recognize a
separate N connection.  In that case, the owner should tie G from the
amplifier power cord to the neutral wire from the breaker box, and
also to a bare ground wire from the breaker box, if one exists.   That
is not ideal, because the return current is then shared between N and
G, but it is an acceptable practice, since N and G are already tied
together at the breaker box and are very nearly always at the same
voltage.  Thus tying N and G together on an amplifier chassis does not
create a safety problem. Unfortunately, because return currents are
then shared between N and G, one can experience hum and other
irritating secondary problems.
73,
Jim w8zr

Sent from my iPhone

> On May 3, 2021, at 11:46 PM, Victor Rosenthal <k2vco.vic at gmail.com> wrote:
>
> Regardless of hum issues, the 220v 3 wire receptacles should be connected
> to ground, not neutral. It's a safety issue.
>
> Victor 4X6GP
>
>> On Tue, May 4, 2021, 04:26 <w5cul at sbcglobal.net> wrote:
>>
>> All,
>>
>> First Thank You to all who replied!!!  I received a lot of replies off
>> list,
>> too many to answer individually.  So I will attempt to answer all the
>> questions in this one response as best as I can.  It does appear that I
>> need
>> to add a little more detail surrounding my setup as a lot of the questions
>> were centered around that, and then some about how the Amp was wired
>> itself...etc.  So here goes.
>>
>> It is a 3/6 cable with a ground wire that runs from the Main Electrical
>> House Panel to a 4 Pole 50amp Dryer Receptacle in the bedroom.  From there
>> the sub-panel is plugged into the dryer receptable using a 4 Pole Dryer
>> Plug
>> (L1,L2,N,G) .  2ea 120Vac and 2ea 220Vac Circuits come out of the
>> sub-panel,
>> each with their own CB.  One set of 120Vac receptacles are wired into L1,
>> Neutral and Ground.  The other is wired into L2, Neutral and Ground.  The 3
>> Pole 220Vac Receptacles are wired to L1, L2 and Neutral, more on that
>> later.
>> One gentleman asked me why 2 independent 120Vac Circuits, why not use just
>> one 15amp Circuit for all the 120Vac needs?  I split out 2ea so that I
>> could
>> balance the load across L1 and L2.
>>
>> Another Gentleman discussed a 4 Pole Dryer Receptacle versus the older 3
>> Pole Receptacle, and that was much appreciated as it jogged my memory of
>> how
>> I had this setup at my father's house when I was having to take care of him
>> in Mississippi.  I did not run a dedicated 220Vac to the bedroom where I
>> had
>> a temporary station setup, yet just borowed from his Dryer Receptacle that
>> was in the laundry room across the hallway when the dryer was not in use,
>> which was not too often.  And his Dryer Receptable was the older 3 Pole
>> type, L1, L2 and N.  And that answers why I wired the 220Vac Receptacle off
>> the Sub-Panel that was feeding the Alpha at that time the way I did.
>>
>> The 220Vac line coming out of the Alpha is wired into a 3 prong plug, L1,
>> L2
>> and a "Green Wire".  After re-reading the 87A manual this morning, it does
>> say that the Green Wire can either be wired to Neutral or Ground, stated in
>> that order.  So, when I wired up the 220Vac Receptable all those years ago
>> for use in my Dad's house, I wired the 3rd prong to Neutral such that the
>> Alpha's Green Wire will be connected to such.  The manual indicates it can
>> be wired either way, to N or G.  While under use at my fathers house, there
>> was no low level 60Hz hum in the speakers, but then it was not a true 4
>> pole
>> service like it is here now.
>>
>> After coming back from Mississippi permanently, I just recently started
>> getting this station back together.  Keeping in mind that the Dryer Plug
>> for
>> the Sub-Panel was setup for 3 Pole and that it can plug into a 4 Pole
>> Receptacle, I did use that arrangement to temporarily get power to test out
>> the Alpha after the big move.  During that recent testing, prior to having
>> a
>> dedicated 4 pole 220Vac Line installed into this bedroom, I did not
>> experience any low level 60Hz hum with the Alpha plugged into the
>> Sub-Panel.
>> Keep in mind that all of the 120Vac equipment was being powered by the
>> "Bedroom" Circuit at that time, not this new 4 Pole 220Vac Circuit.  So
>> this
>> is prompting me to rewire the 220Vac Plug and taking the Alpha's "Green
>> Wire" to Ground as opposed to the Neutral and see what happens.
>>
>> And lastly, a Gentleman asked me about Station Grounding, is all the
>> equipment bonded together and is there a Station Ground.  There is no
>> Station Ground at this time, it is floating, or using the Ground that comes
>> in from the 4 Pole 220Vac Circuit.  I plan on installing such this weekend.
>> Not just a "Ground", but an RF Ground that extends from ground rod to
>> ground
>> rod that are appropriately spaced from each other and that are bonded by
>> copper shielding.  As for the bonding of the equipment to each other, that
>> is actually being accomplished by the Coax cabling that interconnects the
>> equipment.  The SO239 connecters are bonded to the equipment chassis, so
>> when you connect up a Coax from one piece of equipment to another, you are
>> affectively bonding those chassis together using the ground shielding of
>> the
>> Coax.
>>
>> So I think my first step is to re-wire the 220Vac Receptacle that is
>> feeding
>> the Alpha and see if that helps.  If that does not eliminate the hum, the
>> next is to replace the Caps in the Transformer Line in the Alpha, one may
>> be
>> leaky as one Gentleman said.
>>
>> Again, Thank You all for your replies, advice and guidance.  I certainly
>> have some more ideas now and a path to move forward with.
>>
>> Thank you,
>>
>> Mike
>> W5CUL
>>
>>
>> -----Original Message-----
>> From: Amps <amps-bounces at contesting.com> On Behalf Of w5cul at sbcglobal.net
>> Sent: Monday, May 3, 2021 12:26 PM
>> To: Amps at contesting.com
>> Subject: [Amps] Alpha 87A Power Supply Question
>>
>> Good Afternoon Gentlemen,
>>
>>
>>
>> I have a rather quirky situation and a question about it.  I have been
>> chasing down a low level 60Hz hum I get across my speakers when I plug my
>> Alpha 87A into a shared A/C Service for the shack.  I say shared because I
>> am referring to a dedicated 6AWG 220Vac line that runs from the Main
>> Electrical Panel for the house to the shack (bedroom).  From there it is
>> connected to a Sub-Panel that splits out 2ea 220Vac Lines and 2ea 120Vac
>> Lines all with appropriate CBs.  All the 120Vac equipment to include
>> Transceivers, computers, speakers etc...are powered by the two 120Vac
>> lines.
>> The Alpha is powered by one of the 220Vac Lines.  So as the issue goes,
>> with
>> all the 120Vac plugged in and powered up, transceiver turned on, white
>> noise
>> emanating from the speakers, the moment I plug the Alpha 87A into one of
>> the
>> 220Vac sockets, CB turned off, I immediately get a low level 60Hz hum
>> coming
>> out of the speakers.  Since this sounds like a neutral or ground feedback
>> loop, it prompted me to check the wiring on the Alpha.  So I unplug the
>> Alpha and perform a continuity check from Leg 1 of the plug to the chassis
>> of the Alpha, Leg 2 to the Chassis and Neutral to the Chassis.  As for the
>> 120Vac Legs, there is no continuity to the Alpha Chassis.  But there is
>> direct continuity from the Neutral of the 220Vac Alpha plug to the Chassis
>> of the Alpha.  So the question I have is should the Neutral on the Alpha
>> plug have such continuity to Chassis Ground, or do I have a bad Capacitor
>> somewhere in the Alpha?  I will say that the Alpha 87A does operate as it
>> should and does put out full power.
>>
>>
>>
>> Thank you in advance,
>>
>>
>>
>> Mike
>>
>> W5CUL
>>
>>
>>
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