Astin Trew AT1000 Betriebshandbuch - Seite 9

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C. Remove the top plate, place on a

non-scratch surface to

prevent marking.

You are now ready to change the

valves.

Valve life.

We recommend the valves are

replaced every 20,000 hours. At end

of life, valves start to make the sound

'soft' or 'out of focus'. Valves rarely

just stop working. Occasionally they

will start to audibly buzz before end of

life and it is necessary to change

them.

As a guide, using this amplifier four

times a week for an average four

hours a session for 48 weeks a year;

we would be recommended to change

the valves once every 15 - 20 years.

If you leave your equipment on all the

time, we recommend changing them

every two years.

This pre-amplifier is designed to use

the ECC82 (12AU7) valve.

There are a number of manufacturers

of this valve and a large quantity of

'new old stock' (NOS) types also avail-

able. Spare ASTINtrew valves can be

purchased through your dealer or dis-

tributor.

Changing valves: Remember, valves

run hot when in use. Wait an hour

after switching the amplifier off and

removing the mains / signal cables

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 force the valve into / out of

the holder. This could bend the cir-

cuit 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, so as

each of the nine valve pins is pulled

/pushed in turn (gently).

When inserting a valve, first ensure

the pins are not bent on the valve,

then locate the pins onto the valve

holder correctly, by aligning the 'spac-

ing position' on both valve and holder.

Remove white teflon valve damper and

replace on new valve in same position.

Ensure no items such as tools or

spare parts are left inside, replace the

top plate, noting the front and back

screw positions are different, re-fit all

10 Alan screws. Do not to over tight-

en and damage the screws or key.

Changing the fuse:

The fuse holder is located on the back

plate within the IEC mains socket cas-

ing. A spare 20mm glass 500mA

fuse is located within the fuse carrier.

The UK 13A plug is also fused.