Astin Trew AT5000 Manuale operativo - Pagina 8

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the valves are replaced every 20,000
hours. This is conservative and per-
haps represents a two-thirds life
expectancy for these valves
in this design.
This amplifier is designed to use the
ECC82 (12AU7) valve only.
This valve type is very unlikely to go
out of production in the foreseeable
future. There are a number of manu-
facturers offering this valve. Spare
ASTINtrew valves can be purchased
through your dealer or distributor.
As a guide, using this amplifier four
times a week for an average four
hours a session, for 48 weeks a year,
we would recommended you change
the valves every 20 years. If you leave
your equipment switched on all the
time, then we would recommend
changing them every thirty months
(two and a half years).
Changing valves: Valves run HOT when
in use. Wait an hour after switching
the amplifier off before changing
valves.
The valve holders are attached to the
printed circuit board, and the spring
terminals that hold the valve pins are
strong, so care has to be taken not to
damage the board or valve when
removing or replacing them.
Do not pull or push the valve straight
into / out of the holder. This could
bend the circuit board and may result
in damage. The correct way to
remove / insert a valve is to pull /
push gently whilst rocking slightly in a
circular way (do not twist).
Remove by sliding, the white teflon
valve dampers from old valves and fit
on new valves in same position, near
top of valve.
When inserting a valve, first ensure
the pins are not bent on the valve.
Locate the pins onto the valve holder
correctly by aligning the 'spacing posi-
tion' on both valve and holder.
Changing the internal fuses: The fuse
holders and fuses are located close to
the valves on the circuit board. Only
replace with a 20mm glass 2 amp
and 5 amp slow-blow fuses, as indicat-
ed on printed circuit board.
When finished, ensure no items such
as tools or other parts are left in the
amplifier, replace the top plate, noting
the front and back screw positions are
different, re-fit all 10 Alan screws.
Take care not to over tighten and
damage the screw head or key.
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