AllegroKnowledgeBase™
If equipment is over 10 yrs old and has not been used in the last 24-hrs, powering ON without the proper use of a VARIAC will drastically shorten the life of the power supply capacitors. The older the caps and the longer they've been unused, the worse the problem.
How To ReForm Electrolytic Capacitors
Electrolytic capacitors dry out when not biased.
If your equipment hasn't been used recently,
especially if over 10 years old,
following this simple procedure will
improve sound and delay costly repairs.
You will need a "portable" VARIAC
and a "True-RMS " AC Voltmeter.
Note: If meter is not marked "True-RMS,"
the reading will not be accurate.
1) A thorough inspection and cleaning
of all internal parts and verification of
correct mains-voltage and fuse-value is
essential before operating equipment.
Consult a qualified technician.
2) Measure line voltage going into VARIAC.
3) Measure output voltage of VARIAC.
4) Mark scale at UNITY-voltage
(INput voltage equals OUTput voltage).
5) Mark scale at 120 Volts
(or 100-220-240 for your location).
Best to measure late at night
when line-voltage is highest.
6) While reading OUTput voltage (analog meter
is better for this purpose), rotate very slowly
over full range and make sure there are
no "dead" spots on the autoformer wiper.
7) Turn VARIAC control full-CCW to Zero-Volts
Switch VARIAC ON and leave it ON.
Plug component-under-test into VARIAC.
8) S-L-O-W-L-Y and S-M-O-O-T-H-L-Y,
bring voltage up to around 50% of line voltage.
Increase slowly and smoothly 5 Volts at
30-minute intervals (or longer, depending on age
of equipment and how long it hasn't been used)
until you reach your mains-voltage.
* NOTE: It's the exception, but some equipment
(i.e., some Sony) do not like to be run at low voltage.
In this case, bring up initial voltage to 70% of line,
& increase s-l-o-w-l-y from there. If in doubt, consult
Manufacturer's Service Manual or Service Dept.
9) After you reach the target max-voltage,
let it run for 24 hrs (or longer) on the VARIAC.
When finished, dial VARIAC down to Zero before
switching off the component (not the VARIAC!).
Unplug component from VARIAC,
plug directly into wall outlet,
and switch ON.
* Check AllegroKnowledgeBase™ for
How To Determine Best AC-plug Polarity.
* Be aware that [stock] VARIACs allow OUTput
voltage to go way above your line-voltage;
be very careful not to exceed your nominal
line voltage. Keep a plastic cup over the
Control knob to prevent inadvertent operation.
* Design-center for US electronics is117 VAC
("110" Volts-AC went out with the Victrola).
120 is MAXimum voltage you ever want.
Alas, most power companies are feeding
you more than this, as it spins your meter faster,
and they can squeak by with less transformers.
* Some functions may not work properly
when line voltage is brought up slowly
(Nakamichi Dragon is one such example).
When re-forming is complete and the
VARIAC removed, the component will
function normally when hard-started.
Electrolytic capacitors over 20 years old
should be replaced to improve performance
and avoid catastrophic failure.
Soft-starting all electronics
with a VARIAC be a wise move.
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