How to replace Preamp Tubes/Valves
"All valve/tube amplifiers have potentially lethal voltages within.
If you are at all unsure of electronic repair, please take your amp to a
qualified amplifier repair technician."
Firstly, make sure there are no mains power connected to your amplifier.
Then ensure that you have left sufficient time for all the valves/tubes
to cool down as the valves/tubes get EXTREMELY hot when on.
You will then need to remove the metal backing to gain access to the valves.
Here you will see (In the AD30TCH) 3 sets of valves/tubes.
From left to right these are a single rectifier valve/tube,
then 4 power amp valves/tubes, then 4 preamp valves/tubes.
(You should have no need to remove the amp chassis from the casing
to change the valves, I have done this for photographic purposes only.)
You will then need to take out the valves/tubes which you require to replace.
Firstly take of the metal shield around the valve/tube by pushing down on them
and moving them slightly clockwise, it will then pop up due to the internal
spring.
You will then have access to the valve/tube. To remove the valve/tube,
supply firm and
even pressure around the valve/tube and lift vertically.
To insert an new valve/tube, line up the "missing pin" on the valve/tube
up with the "missing hole" on the valve/tube holder:
Once again, supply firm and even pressure down on the valve/tube to fully insert
it in the position. Then put back the removed metal shield
over the valve/tube
by lining up the "dimples" on the valve/tube holder with the track on the shield.