[Boatanchors] Article on changing from 2 to 3 wire power cords

[Maury Guzick]

 Hi Al
Thanks for the info. The HT32 has been in AC for almost a year, so I don't think moisture will be an issue also, the rectifiers have been solid stated. But, I am unsure of any thing else except there has been a relay replacement with the new one hanging unsecured under the chassis. I will start with a new 3 wire power cord and replace the one with bad insulation then do some checks on the transformer and main caps. 

All the best.
73
MauryW5IO

    On Wednesday, August 7, 2019, 1:20:34 PM CDT, Al Parker <anchor at ec.rr.com> wrote:  
 
 Hi Maury,
    The HT-32 is a great xmtr, I use mine weekly.  But there are a few 
"gotchas" in it.
    First off, don't power it up yet (or again).  The HT-32 & HT-37 (plus 
other Halli xfmrs) are prone to picking up moisture if in storage for 
any length of time.  The HV winding will short to one of the 5v windings 
fairly soon after powering up in it's been stored.  If any question, put 
a 60 watt light bulb under it for a day or 3 to warm it up and drive out 
moisture.
    The problem then can be avoided by installing SS diodes in place of 
both rectifiers, and disconnecting the 5v leads from both sockets.
    Second, the bias supply has a selenium rectifier in it that probably 
has gone bad and you won't get enough negative bias voltage on the 
finals to cut them off when you let the key or mike switch up.  If it's 
not too bad, the AC fuse, if it's proper size, will blow after a while. 
If a prev. owner has installed a bigger fuse, and the bias voltage is 
too far off, the finals will melt down.
    You can see some of my experiences with the HT-32/37's at 
<http://boatanchors.org/HT37.htm>  The SS diodes are covered abt half 
way down the pg.  I don't think I've put anything out on the bias 
rectifier fix, but a small SS diode will do the job, but since it has 
much less voltage drop it will need a dropping resistor added at its 
output.  IIRC, 2k-3k will be reqd.
    The fan will probably be noisy, if not now, after a while.  Replace it 
with a small fan from a PC or elsewhere, with a proper pwr supply to it. 
  (blowing out).
    The AC line is isolated from the chassis, no problem with that.  When 
you install a 3-wire cord, wire the hot (black wire to the fuse, and the 
neutral (white) to the other line, xfmr primary.  The green wire to any 
convenient ground point.
    I hope this is of some help to you,
73,
Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 8/7/2019 10:08 AM, Maury Guzick wrote:
>  I appreciate all the replies.
> 
> I have been replacing worn out 2 wire power cords with newer 2 wire cords of similar style on radios with one side grounded to the chassis.
> 
> I am at the moment looking at bringing back to life a HT-32 I got for $10. But the AC is or has been lifted off the chassis. There have been a number of mods under the chassis. So I want to have a better understanding of how to rewire the power cord.
> 
> I also am looking at some antique radios that are AC/DC types that will need new cords, so this inquiry is multipurpose.
> 
> 73MauryW5IO
> 
> 
> 
>      On Tuesday, August 6, 2019, 7:17:20 PM CDT, Eric <vzwengr at gmail.com> wrote:
>  
>  My very unlearned opinion.....
> 
> 
> Connecting a supposed to be floating metal cabinet to the grounding wire
> and then using the hot and neutral wires to connect to the chassis
> inside the cabinet would protect against the cabinet from "going hot".
> As far as I know this is the entire purpose of the grounding wire.
> 
> If the cabinet is wood, plastic or some other insulating material,then I
> can't see any reason to install a 3 wire cord & plug.
> 
> 
> Eric
> WB6TIX