Hello Eric,
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Sorry, I'm a little late to the party on this one, however I will inject my 2-cents worth...
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I have a few Henry amp's (four, to be exact) as well as several other brands & models (i like amp's!).? I'm also a commercial/industrial electrician (40+ years, retired) but continue to do a lot of residential & small commercial work.
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Anyway, a few things to note here, regarding the supply power issues:
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For whatever reason, Henry built a LOT of amplifiers that "required" a neutral conductor in addition to the two "hot" legs (220-240v). Also, since 3-wire cord was (and is) very common, Henry decided to use it? for 240 operation (instead of a proper 4-wire cord, red/black/white/green), and utilizing the "green" conductor as a neutral.? This was a very poor design choice IMHO (and somewhat illegal by modern standards), but there it is... Thank you Ted Henry. Unfortunately, this prevents you from being able to properly "ground" the amplifier's case back to your house's utility grounding point (i.e. the equipment ground). This could allow the amp's metal case to become energized in event of an internal fault, and cause a shock or electrocution.
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However, this can be easily remedied. No neutral is "required" to run your amp (as explained below)... only "straight" 240-volts (with a proper equipment ground), and with utilizing the proper plug on the amp's cord: either a NEMA 6-15P or a 6-20P plug, with the matching receptacle (NEMA 6-15R or 6-20R), depending upon whether you want to supply 15 or 20 amps to the amp. BTW: a 15 plug will plug into a 20-amp receptacle, but a 20-amp plug will NOT plug into a 15-amp recep.
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Now, let me stop for a moment to provide a quick explanation of U.S. single-phase power (In case you're not aware):? In the standard US power scheme, there are two "hot" conductors, and a"neutral" conductor. This "neutral" conductor (typically the white or gray wire) is derived by center-tapping the 240 transformer winding, and then bonding that to ground (literally).? This is why it's commonly called the "grounded" conductor, because it is literally attached (bonded) to the earth at your service entrance or meter panel (and also inside the utility co's. transformer).? This "grounded" neutral conductor should not be confused with the "grounding" conductor (usually a green or bare wire). This "grounding" conductor - also commonly referred to as the "equipment ground" or "safety" ground (or just "ground") is also connected (bonded) to the neutral/earth connection inside your service entrance panel.? It is there only to carry any ground-fault currents back to the load center/panel, so a circuit breaker can trip. From that point out, the NEUTRAL and the GROUND conductors, are always separate conductors. They are NEVER (or shouldn't be) tied together anywhere else in the system.
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The neutral (white/grounded) conductor IS the current-carrying conductor (along with the "hot" conductor(s)), and is what gives us 120-volts supply from the 240-volt system. Up on the utility pole, the 240v transformer's secondary winding is center-tapped, and that center-tap is grounded (again, literally to ground), and becomes the neutral conductor.? This is why you can get shocked by the hot conductors in a system, if you are grounded. In any case, those two "hots" and the neutral, provide your house with both 120 & 240 volts of power.
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Okay, now back to your Henry amp: Your Henry amplifier requires 240v to supply the HV transformer primary. However, the primary winding in your amp is actually two 120v windings in series, and thus, you have a center-tap point on that primary winding.? Inside the amp, it is the cooling blower and 12-volt relay transformer that require 120v, and thus why Henry wanted a neutral supply wire.? But...
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If you refer to the 2K-4 schematic for the power supply (first screenshot below):
The AC input black wire (we'll call this "L1") goes to TB201, terminal 7, then out, through CB1 (the main power switch & breaker), through a protective relay (RY201), then into one end of the HV transformer (T201), term. #1.? Likewise, the white wire (we'll call this "L2") goes to TB201, term. 11, then follows a similar path as L1, and then ends up on the other end of the HV transformer, term. #4.? The remaining two transformer connections (#2 and #3) form the center-tap, and are connected back to TB201, terminals 8 & 9, which are tied together (with no other connections). Therefore, you have two 120v windings in series (1-2, and 3-4), which require a 240v input. Therefore, If you supply the transformer with 240v on terminals 1 and 4, you will have 120v on term's 2 and 3, (relative/referenced to either 1 or 4).
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The remaining AC input wire - the "green" - which is connected to TB201, term. 10, is what Henry used for the "neutral" supply conductor for the amp, to supply the 120v needed for the blower and 12-volt relay transformer (T101). By the way, Henry also placed a fuse (F2) in that internal neutral supply line (this was not a good idea; you should never "open" a neutral - but there it is...).? This was Henry's design.
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HOWEVER, connection of an AC neutral to terminal 10, is NOT required for the amp to function correctly. In other words: a neutral AC-input supply wire IS NOT NEEDED TO RUN THE AMP.? By simply adding one jumper to TB201, you can utilize the HV transformer's center-tap to provide the required 120v.
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With reference to the 2K-4 schematic below (I removed some of the clutter for clarity):? By jumpering between terminals 8, 9, and 10 (on TB201) - and with no other external connections (i.e., no outside wire coming in) - the blower and relay transformer (T101) will get their needed 120v from the HV transformer's center tap (yes, just like a utility transformer).? Then, you can utilize the "green" cord conductor as the proper equipment grounding conductor.? It can be connected directly to the case of the amp.
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I have utilized this very modification (if you can call it that) to 3 of my Henry amplifiers, that previously "required" a neutral from the AC supply.? They have all been in service for several years without any issues.? It's simple, and it works.? In fact, other amplifiers (not to mention, lots of industrial and commercial equipment) utilize this exact arrangement, to derive 120v (from 240v) for internal use. It is ubiquitous...
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As far as your 240v receptacle: If you are planning on running a dedicated 240v line to your shack, and unless the run of wire is very long, you can use regular 12-2 NM cable (aka, "Romex"), with black/white/bare conductors, and a suitable 20A, 2-pole circuit breaker in your panel. The white wire should be re-identified - at each end - with a [preferably] a red mark (like tape) to identify it as a hot conductor. Obviously, the bare conductor is the equipment ground (not a neutral!). If the wire-run is long (more than say, 50-70 feet) I would up-size the conductors to #10awg (10-2 "Romex"), but still only supply it with a 20-amp breaker. The larger wire size will help reduce any loaded voltage drop.
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Inside your shack, you can install the appropriate receptacle box (enclosure) and 240v receptacle. I would use the 20-amp version (NEMA 6-20R) since it will accept both the 15 or 20 amp plugs.? These single receptacles are readily available from stores like Lowe's or HomeDepot, as are the plugs. If you wanted a duplex-type receptacle (similar to a standard 120v type), Leviton makes them, and they are available through Amazon (HERE: ).?
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Hope this is helpful... good luck!
