POWER CORD REPLACEMENT QUESTION..

[fleis...@comcast.net]

Hi all, I have to replace the power cord on an RCA 29K that HAS a
transformer. I'll be using a bladed replacement. Does it matter to
which point the larger blade of the plug is connected.

Would the lager blade go to the power switch? I know in a hot chassis-
non transformer set its very important, but with a set with a
transformer does it matter if the wide blade is to the power tube or
power switch?

All your expertise is greatly appreciated.

Thanks!!

Barry F.

[paul @removeppinyot.removecom Paul_P]

<fleis...@comcast.net> wrote in message
news:deff2841-25d9-4698...@a32g2000yqm.googlegroups.com...

Barry,

This is what I do when establishing the Phase or Hot and Neutral of a
transformer chassis.

Given:

Wide Blade on plug is Neutral (the wide blade on the wall outlet SHOULD be
neutral. It should be tested).

Thin blade on plug is HOT.

The Hot wire (thin blade) should go to the switch and be switched.

More technical Givens.

Transformers will produce leakage voltage and current to their metal frames
and therefore chassis ground. *This can be measured with a voltmeter from
the unit's metal chassis to the U ground in the wall outlet, metal water
pipe or convenient earth ground. **To measure current place a 10,000 ohm
resistor across the volt meter. You now have a current meter where I=E/R.
The voltage reading should significantly drop with the 10,000 ohm resistor.

The leakage voltage/current will be different depending on how the primary
wires are connected to Hot and Neutral.

The transformer primary should be connected to the line (hot and neutral) as
so there is a minimum of current leakage from chassis to ground. This takes
a little experimenting.

If all this seems too much - connect the thin blade so it is headed to the
switch. Neutral should NOT be switched.

All of this may change depending on your specific situation and equipment.

Ask more questions if needed.

Good Luck,
Paul P.

[Martin Crossley]

I'd use a 3-core one, connecting the green (or green/yellow) to chassis and
not worry about which way the primary is wired,
but, as per Paul, definitely have any fuse and single-pole switch in the
live/hot.
Martin.

[Michael G. Koerner]

I also wire a fuse between the hot wire on the cord and the switch on my
transformer-based sets if one is not already there. I would use a fast-blow
fuse with 0.5 amps for every 3-4 tubes in the set.

If you chose to include a bucking transformer to knock some voltage off of the
line (line voltages are higher today than they were when these sets were new -
by about 10 volts or so, low-mid 120s now vs. low-mid 110s then), wire it on
the hot side of the line between the switch and the set's power transformer.

The line bypass 'safety' capacitor also goes between the hot side of the line
between the switch and the transformer(s) and the grounded chassis.

--
___________________________________________ ____ _______________
Regards, | |\ ____
| | | | |\
Michael G. Koerner May they | | | | | | rise again!
Appleton, Wisconsin USA | | | | | |
___________________________________________ | | | | | | _______________

[paul @removeppinyot.removecom Paul_P]

> I also wire a fuse between the hot wire on the cord and the switch on my
> transformer-based sets if one is not already there. I would use a
> fast-blow fuse with 0.5 amps for every 3-4 tubes in the set.

One consideration on the fuse type, There is an inrush current. A Fast
blow may give you headachs or cause one to increase the ampreage (of the
fast blow) too high. Consider a standard or MDL time delay.

That said, I do not have nore have I properly calculated a fuse value in my
carreer. You are on your own. But here is a place to start:
http://www.littelfuse.com/design/application-design-center.html?cm_sp=Marketing-_-Application%20Design%20Center%20Banner-_-1

Paul P.