Soldering iron, solder wick,
soldering heatsink, electrical tape, small cable ties, nonacidic RTV, Outlet
tester (usually < $10 at a hardware store.)
1) Mark the side of the adapter with the
wide plug as "FOR TEST ONLY." Mark the narrow side as "HOT".
2) Turn the switched wall outlet off. I prefer
to check the outlet with an outlet tester. If you don't have one, at least
verify that the switch works with a desk lamp if you are not sure that
the switch works.
3) With the wall socket adapter (cheater plug) unplugged
from everything, modify/cut the cheater plug's polarization tab so that
the 115V Cold tab (wide one) is the same size and shape as the smaller
hot tab. Clean off any and all metal filings.
4) Unplug the UUT (Unit Under Test -- the piece of
electrical equipment you want to "polarize") from everything.
If it has a volume control, set the control at minimum.
5) With an alligator clip, attach the metal chassis
of the UUT to one side of an AC voltmeter. Set the voltmeter to the 100V
or 200V AC range. Remember what I said about being careful and qualified.
If this even makes you nervous, buy a technician friend of yours a Dr Pepper
and after he does the work, a beer and a pizza.
6) With another alligator clip, attach the remaining
AC voltmeter lead to the metal chassis of a reference piece of electrical
equipment that is three pronged and that is plugged into the wall. As a
second choice, check your outlet with an outlet checker (I've seen miswires)
and use a banana plug to attach the voltmeter to the ground hole. If you
don't know which one is ground, buy a technician friend of yours
a Dr Pepper and after he does the work, a beer and a pizza.
The UUT should be switched
on at this point, the UUT's wall outlet MUST be off.
7) Check the three prong adapter for metal dust again,
put the modified cheater plug on the UUT and plug the UUT in to the switched
wall outlet with the side marked "FOR TEST ONLY" into the wide slot.
8) Double check that the meter is on AC volts. You
may see up to 1-2 V at this point.
9) Stand clear of your UUT and flip the wall switch
on. If the UUT is tubed, let it warm up. DON'T TOUCH the UUT. Read the
voltmeter and write the voltage down next to the words "STOCK". If you
see anything close to 115V, shut the switch off, the equipment probably
is seriously defective.
If you saw 115V, you'll be
darn glad you weren't touching it when you flipped the switch.
10) Turn the wall switch off.
10) Unplug the cheater and plug it in upside down.
11) Stand clear of your UUT and flip the wall switch
on. If the UUT is tubed, let it warm up. DON'T TOUCH the UUT. Read the
voltmeter and write the voltage down next to the words "FLIPPED". If you
see anything close to 115V, shut the switch off, the equipment probably
is seriously defective.
12) Turn the wall switch off.
13) Remove the modified cheater adapter and lock it
up someplace safe.
On my Foreplay Preamp I got off easy, STOCK was 9.4V RMS and
FLIPPED was 33V RMS. On my Dynaco MK IIIs, the reverse was true and I had
to solder in them.
14) If the "FLIPPED" voltage was lower than
the "STOCK" voltage by more than 10% the following modification may help
your system sound better. . .
Unplug the UUT (Unit Under Test -- the piece of electrical
equipment you want to "polarize") from everything. Or should
we call it the UUM (Unit Under Modification). Wait a couple minutes for
all the capacitors to bleed down.
Using the red lead, ohm from the UUT wide plug and narrow plug (at the
same time) to UUT chassis.
Chassis must be probed using the black lead.
RECORD this reading.
Take the cover off (there goes the warrantee) and check the all capacitor
voltages to make sure they are less than 9 V DC. Remember, your voltmeter
was on AC, you need to use DC. Take a good look at the internal wire dress.
You'll need to return it to this condition after you are done.
Find the primary of the transformer. Unplug/Unscrew/Unsolder the primary
leads and flip them. USE THE SOLDERING HEATSINK on the wires to keep from
melting the wire insulation. This flip must occur at the transformer, not
before the EMI filter, not before any lightning protection! If you flip
the wires before the EMI/ lightning filter, you may generate a shock
hazard.
Check your solder joints.
Check for solder balls.
Check for stray wires.
Check for wire clippings.
Check for nicked wires.
Clean your solder joints.
Check the wire dress to make sure it is just as safe and pinch free
as it was before you opened the box. Use cable ties and/or acid free RTV
to tie the wires down if you have to.
Using the red lead, ohm from the UUT wide plug and narrow plug (at the
same time) to UUT chassis.
Chassis must be probed using the black lead.
RECORD this reading.
The reading should not have changed by more than 5%. If it went down,
you may have made a mistake. If it went up, your unit may have been dirty.
Close the box up.
Check out
1) Make sure the switched wall outlet is OFF and the
UUT is not plugged into anything.
2) Attach an AC voltmeter set to 100V/ 200V AC
between the UUT chassis and the ground reference like you did before.
3) Plug the UUT into the wall socket using the unmodified
3 prong to 2 prong adapter.
4) The wall switch must be off and the power switch
on the UUT on.
4) Make sure you are not touching the UUT. If a lead
falls off, turn the wall switch OFF before you touch anything.
5) Turn the switched outlet on. If the voltage
reads with in 10% of the lower voltage you recorded before, you did good.
If it reads higher, figure out what you did wrong and fix it. If it reads
lower, is the meter on AC? Did you clean a lot of gunk out of the inside
of the UUT?
6) Turn the switched outlet OFF.
7) Is the power off? If so, remove the cheater plug
and use your upgraded equipment.
8) If this solved a problem or improved the sound,
you owe me a cold Dr Pepper. Note: The filament snubber does more good.
But correct line polarity is a cheap modification.
How does it work?
One end of the 115V power transformer winding has more effective capacitance
to the secondary and chassis than the other primary end. By placing the
primary side with the least effective capacitance to the 115V HOT,
the noise injection is minimized. The 115V cold is almost always quieter
than the 115V HOT even after the 115V 60 Hz component is removed. The 115V
cold is attached to ground in your service entrance. The 115V HOT has all
the noise made on the entire utility grid running through it at some point.
Please notice that I said effective capacitance, not measured capacitance.
Because of how the transformer is wound and used, it is possible
for the effective capacitance to be different than the measured capacitance.
What's up with the black lead to chassis bit during the ohm testing?
Because some equipment has internal lightning protection in the EMI filter,
changing the color of the lead that attaches to chassis can change the
bias of the lightning protection and give a different reading.
