The AM Forum

A couple questions for those of you who have replaced the stock AC line cord on your Apache transmitter with a 3-wire cord: (1) Did you retain and use the feed-through capacitors C75 & C76 that the AC line cord connects to and, if so, why; and (2) did you use the line cord terminal cover with the new cord or remove it? Any advice you care to offer from your experience would also be appreciated.

I'm planning to replace the stock Apache two-wire line cord/fused plug with a 14 gauge 3 wire cord, fusing both the hot and neutral leads using panel mount fuse holders I will install on the rear chassis apron, and connect the green wire to chassis. There's not much room inside back there so I'm thinking about removing the stock MV filter cap C3A/C3B when I replace with new smaller caps, which should provide enough room for the fuse holders.

73,
Brad

You only need to fuse the hot lead.

Fred

As Fred said, only fuse the hot.  Putting a fuse in the neutral lead is very poor practice and a violation of the NEC.

GMA series fuse holders are smaller than AGC so this will help you with the space issue.

Don't fuze the neutral. 

Bad


Bad


Bad


klc

Brad,

I usually get rid of the line bypass caps.  They were part of the EMI filter when TVI was an issue to contend with.  I do put an MOV or Transorb's across the primary after the fuses.  That provides good transient suppression.  Since I usually replace the tubes with SS rectifiers, I normally use a thermistor in series with one side of the line for inrush protection.  They have thermistors that are safety rated for that application.  Just make sure that the thermistor is mounted well and not near any heat sensitive components since they do get hot. 

Joe, W3GMS

Hey Brad,

   All good advice in this thread, I know this
should be obvious but didn't see it mentioned.

  Please route the Hot lead from your new cord
to the "Rear" lug on your new fuse holder, The
Hot lead should then go to the Power Sw. from
the fuse holder lug closest to the fuse holders
lid.

   Those "Dual Fused, Non-polarized" plugs
were from a day when the National Electric Code,
like the Pirates Code, were merely "Guidelines"!

GL OM

/Dan

  "Wear Shoes".

It's correct to state that the practice is not an NEC violation when it occurs in the equipment.  The NEC is a premise wiring standard, not a products standard.   One can look to organizations like UL & CSA International for products standards.  That said, products powered from a 120V grounded neutral circuit, should fuse only the line side. 

Paul, W9AC

Guys - thank you for the advice and information.

Dan, by "rear" lug, I'm assuming that you mean the lug opposite the opening in the holder for the fuse (see attached), and not the lug that, once installed, would be closer to the rear panel of the transmitter, correct?

73,
Brad

Yes, the HOT side of the line should always go to the tip of the fuse holder, farthest from the chassis. The load goes to the other lug closest to the chassis.

What is the logic behind this?

Thanks

Assuming a person was going to replace a defective fuse, no voltage would be on the end of the fuse nearest to you. Wiring it so the end of the fuse is hot subjects the repairman to possible shock.

  Exactly, Probably more beneficial when the fuse
"Didn't" open! IE Ceramic case jobs where you can't
tell.

"Wear Shoes".

/Dan

WEll Criminy, if the fuse is still good you get blasted.   Pretty small difference in my book, but the guys that write the codes gotta do something I guess.

I guess if the hot tip is combined with the cap that captures the fuse, it all works as planned. 

Thanks

:)

Curt

Also if you take out the fuse the top contact is accessible. You could put your finger in there and get shocked if that was wired with the hot side. Also there would be no fuse protection between that contact and anything that touches it if it were connected to the hot side of the line. It's kinda common sense. I don't think anyone ever told me how to wire it.

So...I probably shouldn't just stuff it full of solder and jam the cap back on until I unplug it?  ;)

C

Aw, go ahead!

73DG

Yo'

   You boy's are missin' the point,

                "Wear Shoes".

73
/Dan

Good points all, but there's a bigger point here: a meter probe is the only thing we should be touching to a plugged in radio's circuitry.

I always use line bypass caps since their purpose is to take any RF to ground and not to your lips when swallowing the lollypop mike ::)

Also in most areas TX TVI/RFI is still possible and I also still use a low pass filter. Maybe that is why my telephone doesnt ring no matter what band Im on 8)

Carl

Makes perfect sense to this Double E.