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Author Topic: L-4PS and 240 VAC  (Read 3347 times)
AB9DF
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Posts: 87




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« on: January 18, 2013, 01:00:14 PM »

I have recently purchased a L-4B and L-4PS and am struggling with the power source.  I have 200 amp service and have run a box over the radios.  I have 4 wire cable running from the circuit box terminating in a 4 wire receptacle.  However, the L-4PS has installed a 3 wire cable.  It is a Triangle cord 14-3 spt-3.  It is a grey cord with two grey 14 Gauge wire and one green ground cord. 

My question is simple, how do you wire a 4 wire cable going into a 4 wire receptacle to a power cord that has only 3 wires?  My understanding is that to get 240 VAC you must have two hot wires, one common and one ground wire.  yet the amp was set for 240 given the jumper placement and likewise the ps was too.  So is it a matter of how I attach the plug on the wire?  I have a matching 4 wire plug but like I said, I have only 3 wires to hook up.  Perhaps I change the power cord to 4 wire but not sure how that would connect in the PS.  I have pictures if anyone would need to see them.  Just let me know

Thanks for any advice you could give me
Rob AB9DF
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KG6YV
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« Reply #1 on: January 18, 2013, 02:18:24 PM »

I believe the 4 wire is the "new" standard whereas in the 60's three was enough.  I was told that the 4 wire convention uses two grounds instead of one (hence the 4th wire).  I would just hook the black and white wires to the plug's line and neutral and hook your green wire to the green (ground lug) on the plug and leave it at that.  Lots of appliances still use only 3 wires for 240VAC.

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KG6YV
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« Reply #2 on: January 18, 2013, 02:20:12 PM »

BTW, that is what I did for my Henry 2KD classis.  The electrician ran me a 240 VAC circuit with a 4 prong plug for that device which has only three wires in the power cord.  He had to run a four wire circuit to the outlet to meet code but he said you don't need two grounds to the amplifier.
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W9GB
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Posts: 2656




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« Reply #3 on: January 18, 2013, 03:33:16 PM »

Quote from: KG6YV
I believe the 4 wire is the "new" standard whereas in the 60's three was enough.  I was told that the 4 wire convention uses two grounds instead of one (hence the 4th wire).  I would just hook the black and white wires to the plug's line and neutral and hook your green wire to the green (ground lug) on the plug and leave it at that.  Lots of appliances still use only 3 wires for 240VAC.
I believe .... I was told ... Know NEC, do NOT provide guesses about AC residential wiring.

Quote from: AB9DF
The Drake L-4PS has installed a 3 wire cable.  It is a Triangle cord 14-3 spt-3.  
It is a grey cord with two grey 14 Gauge wire and one green ground cord.  
Rob -

North America AC electrical wiring is standardized by NEMA (National Electrical Manufacturers Association) Connectors for residential and light/commercial buildings.
Familiarize yourself (memorize) proper usage.
http://en.wikipedia.org/wiki/NEMA_connector

Your Drake L-4PS power cord (3 wires, 14 AWG) for traditional 240 VAC wiring is normally terminated in a NEMA 6-15P (15 amp) Straight Blade Plug.

The wall receptacle for that plug would be a NEMA 6-20R (T-slot, accept 15 or 20 amp plugs) Straight Blade Receptacle on a 240 VAC, 20 ampere circuit breaker on your main electrical panel.

That circuit would use 2 HOT wires L1 (black) and L2 (red) and Safety GROUND (SG, green wire).  
The NEUTRAL (white) wire is NOT used in this instance, since the Drake L-4PS was manufactured before 1996 and has an AC transformer with 240 VAC primary (No line side 120 VAC components).
===
Quote from: AB9DF
I have 200 amp main electrical service and have run a box over the radios.  
I have 4 wire cable running from the circuit box terminating in a 4 wire receptacle.  
The usage of 4 wires (conductors) is not unusual for NEW 240 VAC circuit wiring by licensed electricians.
IF this is an existing outlet, is this a Dryer outlet in a laundry area ?  
What is the AWG of wire used and amperage of circuit breaker for this circuit?

PLEASE identify the Wall Receptacle at this location.  Is it a NEMA 14-20R receptacle ?

The National Electrical Code (NEC) was changed in 1996, introducing NEW requirements for wiring of 240 VAC appliances (electric range, combination washer/dryer) that have 120 Volt and 240 Volt components.
Ranges, Dryers and Ovens Now Require 4-Wire Receptacles and Cords. NEC Section 250-60

It dictated that all Dryer (laundry) and range ovens (kitchen) receptacles installed after 2000 must have a four-wire type connection (NEMA 14).  Some appliance companies moved to the new connector before 2000.
Therefore, dryers and range ovens manufactured from 1996 to 2000 can have either connector.

The four-prong connector (NEMA 14) has a separate GROUND wire plus Three Poles.
Two of the poles are HOT wires, and the third is a NEUTRAL wire. They still have a 240-volt rating.
The stipulation requiring the switch to four-prong connectors appears in Article 250, Section 140 of the National Electric Code.
The NEMA 14-30 (30 amp) and 14-50 (50 amp) are Four-Prong connectors used for these appliances.  They have a rating of 250 volts, and replaced the previous NEMA 10 connectors used from 1947-1996.
==
Once we have some answers (above) ... specific to your situation ... a specific answer can be provided.

73 de Greg, w9gb
« Last Edit: January 18, 2013, 04:33:17 PM by W9GB » Logged
W1QJ
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« Reply #4 on: January 18, 2013, 05:18:41 PM »

W9GB is exactly correct but his answer is a bit wordy.  Simply put, you have all the wires you need in your box that contains the 4 wire outlet.  Remove the 4 wire outlet and install a 6-20R outlet connecting the red and black wires to the hot screws and the green or bare wire to the screw that is green (ground).  The white wire will not be used.  Cap it off and leave it in the box.  Install a 6-20P plug on the amp cord putting the black and white wires on the 2 hot terminals of the plug and the green wire on the green screw.  You're done.  Good Luck.
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W9GB
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Posts: 2656




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« Reply #5 on: January 18, 2013, 08:33:05 PM »

Quote from: W1QJ
W9GB is exactly correct but his answer is a bit wordy.
Lou -
I follow Patton's motto: Never pay for the same ground twice.

BTW, when North American 3-wire Flexible Cable (black, white, green) is used for 240 VAC; the convention is to use red heat shrink or tape on the white wire.  So, the Hot L2 wire is not mistaken (inadvertently) as a Neutral conductor.

European Union and UK electrical cordage is a larger challenge, since reunification in 1989, working toward color code Harmonization (HAR).
http://en.wikipedia.org/wiki/Electrical_wiring#Color_code
« Last Edit: January 18, 2013, 08:43:51 PM by W9GB » Logged
AB9DF
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Posts: 87




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« Reply #6 on: January 19, 2013, 02:59:08 PM »

Thanks everyone for your help. Got my l4b running. I have a Yeasu 897d
And I am not sure how to trip the amp upon keying. Does any have the same radio hooked up that might be able to help get this amp operating? 
Thanks!
Rob Ab9df
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W9GB
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Posts: 2656




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« Reply #7 on: January 19, 2013, 06:31:32 PM »

You will need to DIY BUILD the cable or BUY a pre-made cable to key the T-R relay in the L-4B.

Its "relay" activation contacts are a 2-pin connector labeled "VOX" (on the amplifier).
The other end of that cable connection must go to the 8-pin DIN socket on the rear of the FT-897.  
You will need the 2-pin "VOX" plug for your L-4B (hopefully your Drake came with it).

The Drake L-4B was designed for the vacuum tube based Drake 4-series radios,
BEFORE modern solid-state radios since 1980.
You will require a external relay interface such as Ameritron ARB-704
http://www.ameritron.com/Product.php?productid=ARB-704

OR modification of the Drake L-4B with addition of a "soft-key" such as Harbach's SK-401.
http://harbachelectronics.com/main/page_products_drake_l4l4bl7.html
The SK-401 safely acts as an amplifier interface to your modern transceiver to the Drake L-4 or L-4B.  This unit mounts inside the amplifier and transforms the 24-27VDC key closure to approximately 1 VDC at 1.5 mA.  
Without it you run the risk of severely damaging the keying circuit in your transceiver.


HF Amplifier Interfacing is covered on page 10 of your Yaesu FT-897D Manual.
Page 18 shows the rear panel jacks.
http://www.yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=102&encProdID=0372FA803B7BBADBF3076C94ACA7A8C5&DivisionID

Drake Notes from 2010
http://www.wb4hfn.com/DRAKE/DrakeHamvention/2010/DRAKE%202010-002.pdf
« Last Edit: January 19, 2013, 06:59:32 PM by W9GB » Logged
N1UK
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Posts: 1572




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« Reply #8 on: January 25, 2013, 09:19:42 PM »

This begs the question, why do we need four pins now and if so, then why didn't they get it right the first time around?

Mark N1UK
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W9GB
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Posts: 2656




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« Reply #9 on: January 25, 2013, 10:17:08 PM »

Quote from: N1UK
This begs the question, why do we need four pins now and if so, then why didn't they get it right the first time around?
Mark,

Long story that starts with Edison, Westinghouse, and Tesla in the late 19th Century ... AC versus DC. Of course, when introduced to Europe (Germany) they settled on 220 VAC.

Sadly, the adoption of NEMA 14 into 1996 National Electric Code occurred after several deaths (consumers and installers/remodelers).
« Last Edit: January 25, 2013, 10:20:06 PM by W9GB » Logged
W1QJ
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Posts: 1496




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« Reply #10 on: January 26, 2013, 03:38:23 AM »

This begs the question, why do we need four pins now and if so, then why didn't they get it right the first time around?

Mark N1UK
Mark, don't misunderstand.  A 4 prong plug is ONLY required on a 240/120v branch circuit NOT on a 240v dedicated circuit.  This is determined by the requirement  of the load.  For a modern day amplifier which is a dedicated 240v and has a 3 wire cord you only need a 3 prong outlet.  That would be 2 hots and a ground (bond).  Not so with a modern day oven for example.  A modern day oven requires a 240/120v branch circuit.  The 4th wire is a white neutral wire which is supplied for the return current of the 120v items used in the oven, like timers and bulbs.  According to NEC there can be no return current flow on the ground (bond) wire so hence the white wire is needed.  The bond only carries current in a fault condition.  The amplifier has no 120v return current so the white wire is not needed.  Although amps have low current 120v items  the 120v is derived from the center tap created by the dual primaries  of the HV transformer.  This became a saftey issue some years ago when stoves and clothes dryers used the ground to carry the current back from a bulb or timer.  If the ground let go the metal of the unit would be hot with return current for the bulb.  If you touched the metal and you were sufficiently grounded you would get shocked. With the seperate white wire that is eliminated.
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AD4U
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« Reply #11 on: January 26, 2013, 06:38:26 AM »

If memory serves me correctly, when changing a L4B and PS from 120V to 240V you have to rearrange jumpers in the PS AND in the L4B at the filament transformer.  Please excuse me if my memory from 40 years ago fails me.

Dick  AD4U
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W1QJ
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« Reply #12 on: January 27, 2013, 05:08:34 AM »

If memory serves me correctly, when changing a L4B and PS from 120V to 240V you have to rearrange jumpers in the PS AND in the L4B at the filament transformer.  Please excuse me if my memory from 40 years ago fails me.

Dick  AD4U

That's correct, you have to go into both units to make the change.  If you look closely at how the Drake power supply switches from lo to hi voltage on the plate you will notice it is a very odd way of doing it.  It is unlike any other amp that switches the plate voltage from lo to hi.  You'll also notice that every newer type 3-500 based amplifier no longer uses this lo/hi plate voltage routine.  this is an old scheme used to comply with the old 1KW DC input/2KW SSb input rule.  SInce we are no longer using that old rule No amplifiers made today switch the plate voltage.  I recommend using the higher voltage scale for all modes and adjusting the drive power accordingly.  I believe the less plate current and grid current required to make the same output than with higher plate current and grid current with the lower voltage is much better all around for the amp and tubes.  I have often considered wiring my Drake amps for full high voltage on the plates at all times and repurposing the cw/ssb switch to add in a small amount of bias like a 5v zener or string of 1n5408's in the cw mode to throttle back the idle current.  That would be the more modern way to do it.
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