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Author Topic: Heathkit SB-1000 AC pulg for 220  (Read 1033 times)
KI4VEO
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Posts: 166




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« on: January 01, 2009, 08:47:28 AM »

I acquired this amplifier and it is strapped for 120 vac.  Since I have 220 readily available I want to wire this amp for 220.

I have an unused 220 electric dryer plug and receptacle available but I recall reading something (don't remember where) to NOT use this style plug and receptacle.

So, I am looking for suggestions.

What are the suggestions?



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N3JBH
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Posts: 2358




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« Reply #1 on: January 01, 2009, 09:30:34 AM »

I would have no idea why the plug you have would not work? Most dryer cords i seen are rated 30 amp's
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N3JBH
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« Reply #2 on: January 01, 2009, 09:35:40 AM »

After looking at the Al-1500 manual Ameritron states a
NEMA 6-15P Plug and that is a common plug i doubt your dryer plug is rated lower then it. and i know the SB-1000 wont pull near enough power to be a problem. Jeff
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W3LK
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Posts: 5644




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« Reply #3 on: January 01, 2009, 09:37:53 AM »

It's overkill, but if you already have them, use them.

73,

Lon - W3LK
Naugatuck, Connecticut
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
KI4VEO
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Posts: 166




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« Reply #4 on: January 01, 2009, 11:49:04 AM »

This is my "intermediate" amplifier.  I also have a Drake L7 which needs some work, but will replace the SB-1000 at some point later this year.

I wanted to wire this outlet with sufficient current overkill to handle the L7.

Thanks for the replies and the good information.

I wish I could remember where I saw the posting on NOT using the dryer receptacle.  There must have been some reasoning.  Perhaps it was a safety thing around children
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WB2WIK
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« Reply #5 on: January 01, 2009, 05:09:11 PM »

There's no legit reason to not use a much larger service branch and receptacle than you need, unless you're afraid of all the "unused amperes" spilling out on the floor so you can trip over them.

The only drawback I can see is that personally, I like to use plugs/sockets that can be "kicked out" by my foot in an emergency.   This is why I don't like "twist lock" 240V connections -- they're fine except you cannot disconnect one by jerking on the cord, and there may be a time that you really want to do that.

The huge 240V dryer outlets and plugs require so much insertion and extraction force that if you "pull the cord" it may not ever disconnect like a smaller 15A plug set would.

Other than that, I can't think of any reason I wouldn't use the much higher-current rated hardware.

WB2WIK/6
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KD0UN
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Posts: 55




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« Reply #6 on: January 01, 2009, 05:26:26 PM »

Each amperage rating has a different plug socket configuration.  It's a way of preventing the user from plugging in a higher amperage/lower amperage device into a line not rated for it.

Rating the line and the associated breaker with the device provides protection for the device.  For example, if you hook the amp to a 50 amp circuit, the breaker won't activate until you have a 50 amp fault.
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K6AER
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« Reply #7 on: January 01, 2009, 08:54:55 PM »

Be careful the SB-1000 transformer is listed for 220 VAC. North America has not has 220 VAC in the homes for over 20 years. Today‚Äôs voltage in the home is 240 VAC. Normally this is not a problem for the higher voltage from the power supply would only be 9% more. Where this would be a problem is the filaments would have a higher voltage and the end result is shorter filament life.  If you filament supply voltage is higher you will need to add some series resistance in order to bring the filament into the specification voltage needed for the tube filaments.

The SB-1000 filament supply was set for 5.2 volts AC. The transformer has no lower voltage taps and input voltage can be only set for 110 or 220 VDC.  When you set your AC voltage input, test your filament voltage to make sure the  voltage is not to high.
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KB1LKR
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Posts: 1899




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« Reply #8 on: January 02, 2009, 05:15:19 PM »

If it's an older (1940's-50's to 1970's??) 3 terminal dryer plug (crows-foot w/ L shaped neutral) it's a 120/240V 30A receptacle with NO safety ground, (at least to the plug, a groundING wire may be present in the box) only 2 hot lines and neutral.

On the other hand if it's a newer 4 terminal dryer receptacle (2 parallel, one L shaped (If I recall, my dryer's gas) and a U ground, then it's also 120/240V 30A w/ ground, and you could use it, however no connection to the white neutral wire is required as you only need 240V not both 240V & 120V.

If the first case, AND a grounding wire (bare or green) is present (likely unless it's really old (pre '60's perhaps??), you could replace the dryer receptacle w/ a 240V/30A (big air conditioner, etc.) receptacle and cap off the unused neutral wire in the junction box. In the latter case you could switch receptacles too, or could cap off the unused neutral inside the amp.

Note dates are approximate, not sure when grounding dryer and range (50A) receptacles became required/common, nor when electric cloths dryers first became common.
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KB1LKR
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Posts: 1899




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« Reply #9 on: January 02, 2009, 05:20:57 PM »

NEMA 6-15P Plug is 240V/15A and will mate w/ either a 6-15R or 6-20R (15A and 20A respectively) receptacle, 20A receptacles (240V & 120V) are the ones w/ one straight and one T slot, so as to take both types of plug.

The dryer should be 30A so won't have any problem supplying an amp.
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KB1LKR
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Posts: 1899




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« Reply #10 on: January 02, 2009, 05:28:03 PM »

http://www.elect-spec.com/nema_flat.pdf
Has lots of plug/receptacle figures. Note: though rated 250V or 125V, nominal residential voltages are 240V & 120V in North America.
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W4MLO
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Posts: 30




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« Reply #11 on: January 03, 2009, 12:50:58 PM »

The really smart thing to do would be to put a sub panel to feed your entire shack from this circuit. If it is a 4 wire just buy a $30 sub panel and feed it directly, if it is a 3 wire just run a same size ground back to the main panel routed with the existing wire. perfectly legal and proper. This way you can run all of your shack from it and have local breakers when needed.

You will love the SB 1000, I do

Good luck,

73 Milo W4MLO
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N1QOQ
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Posts: 188




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« Reply #12 on: January 05, 2009, 07:07:02 PM »

UMMMM No it is not. A grounding conductor MUST be run within the the same conduit or cable assembly. It can not run seprately.

As far a the dryer outlet goes, the old 3 wire outlets
used the neutral as both a ground and neutral. Will it work? Yes is it legal to code? No. This outlet is listed as 120/240 3 wire. I know it is a technicality, but that is code. You can replace the outlet with the correct configuration, they do make a 30a 240 3 wire outlet.

73
Paul N1QOQ
Electrician for 23 yrs
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W4MLO
Member

Posts: 30




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« Reply #13 on: January 05, 2009, 10:17:20 PM »

UUMMM actually it is. NEC Section 300.3 allows that if the requirements set forth in section 250.130 C for branch circuit extentions in EXISTING locations the GROUNDING conductor may be run outside the cable. It is good practice to route it along with the cable where possible.

Wired everything from a car radio to being the project manager over power plant rebuilds..33 years .



73 Milo W4MLO
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N1QOQ
Member

Posts: 188




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« Reply #14 on: January 06, 2009, 05:30:29 AM »

Yup for a replacement recepticle. Not for a subpanel.
You are refered back to 250.130(c) for the rest of the story.

Wire everthing also, but now I also inspect it to.

73
Paul
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