D.W. Fearn VT-1 Instruções de Operação descarregar pdf (Página 36)

D.W. FEARN

VT-1 & VT-2 Microphone Preamplifers

and grade them according to noise, microphonic response, distortion, and other character-

istics. A lo

w-noise tube fr

om us will meet t

he original VT-2 specifications.

The base pins of v

acuum tubes supplied b

y D.W

. F

earn have been chemically treated for low

contact resistance and oxidation prevention. When handling these tubes, care should be

taken to avoid removing or contaminating the treatment. Use a lint-free cloth or paper towel

to a

void direct contact between any part of the tube and your fingers.

Remember that vacuum tubes may be quite hot during operation. Protect your fingers dur-

ing tube replacement. The VT-2 should be turned off before removing tubes. Allow at least

one minute for the filter capacitors to discharge before tube removal or insertion.

Tubes ar

e made of glass and will break if dropped or even bumped in a critical area. Handle

wit

h care.

Electrolytic Capacitors

The VT

-2 is designed and built to last for a long, long time, and it is possible that some com-

ponents (e.g. electr

olytic capacitors) ma

y reach the end of their life long before the equip-

ment becomes obsolete. The electrolytic capacitors used in the VT-2 typically will last at least

enty years. If there is a measurable and/or audible increase in 120 cps noise, the filter

capacitors should be suspected. They should be replaced with new capacitors of equivalent

capacit

ance and voltage rating, and the replacements should be specified for a minimum ten-

ear service lif

Electr

olytic capacitors are also used as plate and cathode decouplers. In choosing a replace-

ment, the same considerations as with the filter capacitors should be followed.

Rot

ary Switches

The r

otary switches in the VT-2 were chosen for their self-cleaning property. In a clean envi-

onment (non-smoking, with frequent room and equipment vacuum cleaning), and with reg-

ular use, the rotary switches should require little attention for years. Audio is not switched in

the rotary switch itself -- the switches only control gold-contact relays. But if cleaning

becomes necessary (as evidenced by intermittent relay switching), we recommend using De-

Oxit (Caig Laboratories). F

ollo

w the instructions provided with the product.

If the switches are not used regularly, oxide and dirt can build up on the contacts. Rotate the

switches through their range a few times on a weekly basis to keep them clean.

The togg

le switches should ne

ver require cleaning.

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