The AM Forum

 :)  I'm rolling right along with this project.  Cid Vance sent me a decent cabinet and a nice front panel.  I'll probably start building this thing next week.  Dumb question time.

I have a DX-20 that was modified with a 3-wire power plug AND a ground lug. I've seen AT-1 xtrs  modified with a simple polarized plug.  The original was "non-polarized" and had no ground lug.  I would prefer to go with a 2-wire polarized and add a ground lug. I've converted a hallicrafters WR-600 to polarized 2-wire, but that was AC/DC to begin with.

Should I tie the "ground" side of a "modern" polarized AC plug to the AT-1 chassis and add a ground lug to the chassis or go with a 3-wire?

My confusion is with the original AT-1 wiring which uses a non-polarized AC plug and NO ground lug.  Since the main function of the "reborn" AT-1 will be as an exciter, it will have to be at the same ground potential as the 813 amp regardless.   ::)

The "newer" 3 prong ground requirement is for safety.  The chassis needs to be returned to safety ground.  Saying that, since your not selling this as a product, hence its a standalone transmitter integrating it into your cabinet and transmitter assembly, I would be content with a ground strap from chassis to a nearby chassis that has a 3 wire cord. 

Its important not to rely on chassis to chassis contact through rack screws and the such, but have a bonding wire to insure safety ground integrity.   

Joe-GMS

Mike, you must be extra careful with everything you're doing with this project.  Check with us often.

To answer your question, DO NOT connect either side of a two wire polarized line cord to the chassis or any other ground.  Connect the hot leg of the cord to your fuse then to the on-off switch then to one primary lead of the power xfmr.  The neutral leg (this is the wide blade on the plug) gets connected directly to the other primary lead of the power xfmr NOWHERE ELSE.  You can then connect the chassis to the station's metal ground point with a separate piece of wire.  OR, you can install a three wire grounding line cord in the chassis.  Connect the black (hot) and white (neutral) wires of the cord the same way I described above.  Connect the green ground wire of the line cord to the chassis with a ground lug.

DON"T get creative with connecting the power cord to your project.  Follow my directions.

Fred

Thanks Fred.  I really don't have a problem with AC as such.  I wired my recording studio with 2 separate 15 Amp 120V branches from a new breaker box fed from the 240VAC mains and split at the box.  Lighting was already sourced from a breaker in the main Service Panel, so I just did some rerouting and created some new branches for distribution.  Though I'm running mainly unbalanced audio, the system is QUIET.  It was inspected by the city engineer and passed with no issues.  Audio is no different than RF when it comes to rack-mounted gear and using the rack for common grounding.  It isn't done. In the studio I have a common ground point that goes straight to a water pipe.

In this case, I was curious because Heath didn't include a ground lug on the AT-1 chassis.  I did a refurbish on a DX-60A a few years ago and replaced the 2 wire unpolarized with a 3-wire power cord.  In this case, I believe I'll go with the "polarized" line cord.  I'll add a fuse and a ground lug because the AT-1 had neither.