• buy • sell • trade •


This and all other pages on this website are for informational purposes only.
Some solid-state & all tube equipment contain lethal voltages; if you are not
totally confident in your ability to ensure your personal safety and the safe
operation of your equipment, take the equipment to a qualified technician.

HARD-starting KILLS electronics!!!
The older the caps & the longer they've
been unused, the worse the problem.

How To ReForm Electrolytic Capacitors

Never operate a vacuum TUBE amp without a Load!
connect Spkrs or Resistor across output terminals
to prevent damage to output tubes & transformers,
and place Shorting-Plugs in the input jacks
to prevent RFI from entering the amplifier.

Electrolytics dry out when not biased.
If Device-Under-Test hasn't been used
recently, especially if over 10 yrs old,
following this simple procedure will
improve sound & delay costly repairs.

A Portable-VARIAC and a
"True-RMS" AC Voltmeter is needed
(if meter is not marked "True-RMS,"
the reading may not be accurate).

1)  Cleaning and a thorough inspection
of all internal parts (especially capacitors -
look for signs of heat-damage, deformation
and leakage) and verification of correct
mains-voltage & fuse-value is essential
before operating Device.

* 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 for the rated mains
voltage of the Device being powered
(100-120-240 Volts AC). Best to measure
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.
Plug Device-Under-Test into VARIAC
and switch Device ON.

8)  S-L-O-W-L-Y and S-M-O-O-T-H-L-Y,
bring voltage up to around 40% of the
rated mains voltage of the Device.
Increase slowly and smoothly 5 Volts at
30-minute intervals (or longer, depending
on age of the Device & how long it hasn't
been used) until the rated mains voltage of
the Device is reached.

* Note: It's the exception, but some Devices
(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 Department.

9)  After the target voltage is reached,
let it run for 24 hrs (or longer) on the VARIAC.
When finished, dial VARIAC down to Zero before
switching off the Device (not the VARIAC!).
Unplug Device from VARIAC, plug directly
into wall outlet (or Balanced Mains Transformer),
switch ON, let it warm up for 72 hrs, and enjoy.

* Check
AllegroKnowledgeBase for
How To Determine Best AC-plug Polarity.

* Be aware that [stock] VARIACs allow
OUTput voltage to go way above line-voltage;
be careful not to exceed the rated voltage of
Device-Under-Test; keep a plastic cup over the
Control knob to prevent inadvertent operation.

* Mains design-center for US electronics
is 117vac; more than this at AC input
to equipment is more $ for your utility
company and your audio repair tech.

* Some functions may not work properly
when line voltage is brought up slowly
(Nak Dragon is one such example).
When re-forming is complete and the
VARIAC removed, the Device will
function normally when hard-started.

Electrolytic capacitors over 20 years old
should be replaced to improve performance
and avoid catastrophic failure.

So what's inside that mysterious can?
An electrolytic capacitor is composed of an anode foil,
a cathode foil, and a separator plate, wrapped and impregnated
with an electrolyte comprised of a solvent, such as ethylene glycol,
and a solute, such as ammonium borate, sealed in aluminum can;
the end-seal is made of rubber, rubber-backed phenolic,
molded phenolic-resin, or polyphylenesulfide; over time,
the electrolyte evaporates through this seal; as the volume
of the electrolyte decreases, the ESR of the capacitor increases
and its capacitance decreases; the increase in ESR leads to
increased heating which leads to further evaporation of
electrolyte, and so on until it eventually fails :-(

Soft-starting all electronics with
a VARIAC avoids costly repairs.

Vacuum tube equipment often has very little safety margin on capacitor voltage
ratings, and equipment originally designed for 115vac operation may be running
on the edge at today's 120~127vac. Power supplies designed for 425vdc on a
450vdc-rated capacitor at 115vac will have 462vdc on that 450vdc cap at 125vac,
a recipe for disaster! The problem is compounded by the higher temperatures
found in tube gear (and high-bias solid-state "Class-A" power amplifiers)!

The Truth About Your Mains Voltage (although the
example below is E.U. 220vac, the idea is universal):
Vintage U.S. electronics was desigined to run on 117vac.
Running it on higher Voltage is not good for the electronics
or your wallet. Your local power company will have you
believe their meter measures only Current, and as Current
goes down as Voltage goes up, it should cost you less.
This diagram from Ashley-Edison says otherwise,
and agrees with my own R&D.

quid pro quo

AllegroSelect VARIACs

Visitor/Buyer agrees that seller/owner/allegrosound/
will not be held responsible in any way for any damages
or injuries brought about by the use of product/service/information.
Visitor/Buyer also affirms that he or she is at least 21 years of age
and has the knowledge/experience/tools to safely handle this material.
Visitor/Buyer agrees to conform to all federal/state/municipal/provincial/territorial laws.
Visitor/Buyer also agrees to indemnify and hold harmless seller/owner/
allegrosound to any and all claims/liabilities/causes of legal action.

−  Established 1973  −
"love what you listen with"
Los Angeles, California USA


AllegroSound et al assumes no responsibility for use or misuse of products, services, info, etc.
design & original content ©AllegroSound, los angeles, california, usa. all rights reserved.

−  Established 1973  −
"love what you listen with"
Los Angeles, California USA
telephone 323.960.5014

> home < > home < > home < > home < > home < > home < > home <

design and original content ©AllegroSound, los angeles, usa. all rights reserved.