Changing Marshall AVT100 Valves

Mark_R

I've owned this Marshall AVT100 since new and its at least 12 years old.  Its not been played much in that time but I want to get it out and start using it.  

I know the valves should be changed, I dont 'think' there is anything wrong with them but they are old so chances are they are not performing as well as they should.  Never attempted this, has anyone here changed the valves on an AVT series amp and any advice before I rip the back off the amp?

DartmoorHedgehog

There's only one valve in an AVT100 (at least there was in mine that was about the same age as yours).  I never changed it in mine - unless there's a problem I wouldn't bother, unless you're curious to see what difference it would make.

From memory, I think there were a few (four?) screws on the top of the case that you have to remove, then the amp chassis slides out of the back.  Then the preamp valve (an ECC83 / 12AX7) is easily accessible.

HHwarner

Its a single 12AX7 (ECC83) in the AVT's, simply just replace (plug and play). If it sounds ok and your not having bother with it, I wouldnt bother though. It wont make much of a difference.

ICBM

The valve will be fine at that age, and especially with little use - ones from the 60s often still work perfectly well.

Preamp valves don't really wear out in the same way as power valves do, although they can go noisy or lose gain - but if the amp sounds OK, no need to do anything - at least not with the valve.

A much more important bit of maintenance with these amps is to clean the fan, if it's even slightly dirty - if it's blocked or stops working the power module will cook itself in a matter of minutes. It is worth taking the chassis out and cleaning any dirt out from the inside and along the heatsink channel as well as the outside of the fan - use a hoover and a soft paintbrush.

Mark_R

Thanks DartmoorHedgehog and HHwarner.  Will leave it in there.  Never looked inside any of my amps, these valves just plug in then?  I feared that I would have to solder them in!

Cheers for the advice ICBM, will give the fan and heatsink a good clean tonight.

not_the_dj

ICBM said:

 use a hoover

Other makes of vacuum cleaner are available ;-)

ICBM

not_the_dj said:

ICBM said:

 use a hoover

Other makes of vacuum cleaner are available ;-)

hoover with a small h, not Hoover with a big h .

Mine's a Nilfisk actually!