Gates BC1 H AC Line input

[K6IC]

Hi all,

Recently picked up a Gates BC1 H,  fairly clean,   but has had some undocumented mods.

First thing that I noticed in the suppkied schematics is that the AC Line input has the neutral  GROUNDED TO THE FRAME.

SSOOOOO,  is it assumed that all broadcast stations use Isolation Transformers to separate AC Line Safety Ground from the antenna's RF Ground ??

In addition,  there have been several mods made,  where 120 VAC loads are taken from line to the Frame -- these are in the form of several Muffin Fans,  and a transformer,  perhaps for meter lighting..   As supplied,  seems that all of the factory loads are line-to-line,  none Line to Neutral (frame).

Recall that NEC requires one, and only one bond from Safety Ground (rod) to Neutral,  and that is at the Service Entrance.

How do you BC rig users,   BC1 H drivers in particular,   deal with this ?  I do have a 7.5 KVA Ultra Isolation transformer,  but its gravational attraction makes it almost impossible to deal with.   Gotta be 250 Lbs plus.

Edit: OORRR,  does one omit  the Safety Ground (green wire) connection to the BC1 H frame,  and use only the RF Ground connection to the frame?  This seems dangerous to me.  This installation will not need to pass inspection.  Even tho did work in Broadcast as a kid,  never did build a station,  or swap out a BC rig.

73   Thanks  HNY   Vic  K6IC

[Mike/W8BAC]

Vic,

I'm not a BC1-H guru by any means but I think what your puzzling over is a 240 volt input rig with the neutral tied to chassis, that's normal. It's not unusual to find 120 volt sub circuits within using one leg of the 240 and chassis for neutral. I hope this helps.

SSOOOOO,  is it assumed that all broadcast stations use Isolation Transformers to separate AC Line Safety Ground from the antenna's RF Ground ??

No, Not ever as far as I know.

Mike
www.w8bac.com

[n2bc]

I don't know the vintage of the Gates...  but I had a Collins KWS-1, 1957ish, where the neutral was tied to the frame.  I think it was fairly common back in the '2-wire' days.   

Heck, I also had a 1939 transmitter that had 1500V on an insulated-from-the-chassis 1/4" phone jack, ON THE FRONT PANEL!  The two meters had a pigtail /w a 1/4" phone plug that you could CAREFULLY stuff into one of the jacks.  OSHA would love that!

Back to topic...  I had an RCA BTA-1R1, 1963 vintage as I recall.  It used 240V (A-phase and B-Phase) and safety ground.  It had a 240V:120V transformer for all the 120V stuff inside (fans, switches, relays, etc.)

Easiest and safest thing for you to do is wire the Gates with a 4-wire cord, lift all the 120V stuff going to the frame and run them to the new isolated neutral and bond the frame to the safety ground.

Be careful in there!

73, Bill  N2BC

[k4kyv]

That's what I did with my Gates BC1-T.  There was one connection tying the neutral to the cabinet.  I simply removed that wire, and ran a separate wire to earth ground from the transmitter cabinet.  That ground wire is tied in with the green wire in the house wiring, and bonded to the service entrance ground via a length of #6 solid copper, buried like a ground radial running from the shack to the house.

[KL7OF]

My BC1-G has the 220V neutral and the RF ground both on the same chassis lug....Was wired that way at the station....

[flintstone mop]

Lucky guy, Vic
The last of the tube transmitters with a viewing window. And using big glass.
Do you have the solid state audio driver?? Solid State exciter??
A transmitter that will do what it was designed to do. Triodes are great pubes.

The others seem right on with their responses for the 220vac connection. That's how I hooked my BC1-H WHEN I HAD ONE................dam another bad decision.

Fred

[k4kyv]

My BC1-G has the 220V neutral and the RF ground both on the same chassis lug....Was wired that way at the station....

So was the BC1-T.  All I had to do was to take off the wire that bonded the neutral to chassis ground.  Since this was about 5 years ago, I'll  have to look inside mine to see if the original neutral  lug was insulated, or if I had to provide an insulated terminal for the neutral.

In the era when those transmitters were produced, electric kitchen ranges also  had the neutral grounded to the metal frame of the stove, so the code must have allowed this on 220v devices.

I have some early copies of the NEC, going back to about 1940.  Sometime when I have a little extra time on my hands, I'll  have to look and see what the code said about this.  Not sure if my most recent copy is new enough to indicate any changes on that topic.

[N0WEK]

The was a code exception for clothes dryers and oven/ranges that allowed the neutral from the 240 vac to be grounded to the frame. The 120 vac loads like motors, lights and timers went from one leg to ground/neutral. All these units used three prong cords.

About 5 years or so ago the code changed and now they need 4 prong cords, and the ground and neutral are separate. The old installations were grandfathered, so you need to know what cord to buy when you buy a new dryer. I just hooked up a new one in a friends house and he had the old system. I used the three prong cord and the dryer came with the neutral bonded to ground with a removable strap.

[K6IC]

OK,   Thanks; Mike, Bill,  Don, Steve, Fred, Greg;

Guess I'll float the Neutral,  Change the fans to 240 VAC,  and perhaps add 240 to 120 VAC transformer to power the small added one.  There may be some additional Neutral connections that I've not yet found,  but will give it a shot.

My Neutral/safety ground bond is more than 250 feet away,  but have a green wire in buried conduit,  and a #6 Ga solid trench ground.  Guess will temporarily connect the trench grouund to the BC 1's frame.  This grounding thing is still a bit of hocus pokus to me -- off-grid with roof-mounted solar panels and so on ...

Fred,  think that this rig is from the 70's.  It has solid-state exciter,  and Audio pre-driver,  to 807's driving the 833A Grids.  Currently has New Chineese 833's  with cast metal-appearing plates.  The tubes have getters, but very little getterization (is that a word ?) on the glass.  Guess that the plates must be tantalum or tantalum coated.

Yea,  am looking foreward to getting that Triode Power on the air.  Wish it has NOS USA tubes,  but will give these existing tubes a run.

73  Thanks again for the input.         Vic

[k4kyv]

Guess I'll float the Neutral,  Change the fans to 240 VAC,  and perhaps add 240 to 120 VAC transformer to power the small added one.  There may be some additional Neutral connections that I've not yet found,  but will give it a shot.

No need for the transformer.  Just run the small fan off 120 volts, using one of the hots and the neutral.  Floating the neutral instead of grounding it to the cabinet should not affect operation of the transmitter in any way.  If there is something in the transmitter that runs off 120 volts by connecting to one of the hot wires and the  cabinet, disconnect the wire that is grounded to the cabinet and wire it to the neutral terminal where the 240 volt  line comes in.

My Gates has a low power position, designed for broadcast stations that ran 1000 watts daytime and 250 watts at night, which switches to low power by shifting one of the leads that go to the plate transformer from hot to neutral.  That puts 120 volts on the primary instead of 240.  This feature still worked exactly the same after I had  lifted the neutral from the transmitter frame.  It is against the current electrical code and is poor practice to ground the neutral to the frame, which may also result in ground loops that produce hum in audio equipment.

[KL7OF]

You may find that the fans (and the noise they make) are unnecessary when the transmitter is run at amateur power levels and duty cycles...

[flintstone mop]

The nice fan that was mounted on the back door of my former BC1-H was just a small fan sound (220vac fan). Not like the clamour of fans in a Collins 20V-1. Those 833's can get the inside of the cabinet very warm without the fan!!

When you get it running, check that if RF excitation is removed that the 833's in the RF final, have a resting current of 200ma. If not they will will take off and have a melt-down..............literally!!!!

The remote control for power adjustment is a beautiful A.C motor through a gear box and a huge variable resistor.

It gets pretty warm in the 1-H, with just the filaments on.

You might have to purchase the fixed ceramic caps if there is a large change in freq. The BC1-H I had was on 540khz.
Are you going to stay around the 1880 something freq??? It's not a convenient transmitter for QSYing. If you're going to change bands, 160M-80M 40m(?) then you'll have to re-design the tank.
I don't know of any Hams who have moved a 1-H to 80M.

Fred

[K6IC]

Good Morning Gemts.

Don,  you are certainly correct regarding the need for a 240/120 transformer.   For whatever reason,  my 240 VAC run into the living room of the cabin,  where the BC1 is (and belongs) is:  two hots and safety ground.   Guess that I was thinking that there would only be a traditional Amp,  not a real transmitter.   Will have to replace that run with four wires.   Have not figured out the cutback power switching yet -- this rig has 250 Watt button,  as well as one for 100 Watts.

Steve,  the small muffin fans often make objectional noise,  but there is not great airflow lower in the front of the box,  where the exciter is located.   Might consider using quiter fans to just move some air.   You are correct that even old-buzzard transmissions should not even warm most of the major components.

And,  Fred,   The fan in the rear door is present in this rig.    Will check the idle plate current on the finals with no drive,  thanks for the tip.
My BC 1 lacks the remote power adjustment option.   The rigs with tetrodes (pentodes)  make this adjustment easy,  as it is commonly a smaller motorized pot on the final screens.

Thanks again to you all for the advice and pointers.   73   Vic

[k4kyv]

The BC1-H I had was on 540khz.

What station was that?  540 used to be considered a clear channel, and only daytimers were licensed to use it. I think the primary clear channel station was in Mexico.  The station I used to work at was on 540.  At 1 kw daytime only, its coverage area extended all the way to St. Louis MO, nearly 250 miles away as the crow flies.  I don't think there ever were a large number of stations licensed on 540, even daytimers.  Later on, the station obtained post-sunset authority, and they ran something like 10 watts.  They still out strapped the 1 kw local  station on 1400.

[flintstone mop]

Hey Don,
My bad, possibly. I'm not 100% certain about the 540 freq. It came from a station in W. bygawd Virginia. It was down at that end of the dial, though.
I paid around $150.00 to change out the G-6 (?) capacitors in the tank. I didn't want to change a lot of things from the stock design. I had no plans for multi-banding.

Fred