Preamp tubes

[frosty55]

My Marshall TSL100 needs the preamp tubes replacing. Can I do it myself, or should someone qualified do it?

[pdf64]

'My Marshall TSL100 needs the preamp tubes replacing'
Why do you think it needs the pre amp tubes replacing?
Have you got a spare 12AX7 that you know to be good?
The user should be able to replace them, just need to be careful. The amp manual should offer some guidance.

[frosty55]

Its just that, for the sake of £30, it wouldnt do any harm to fit a new batch. The amp has done approx 400 gigs with the original ones.....

[pdf64]

Of course it's your call, but I wouldn't bother unless you were concerned about something. Tubes in a head have a far easier life, compared to those in a combo, due to the isolation from speaker vibration.
But get 1 or 2 spare 12AX7 (tested for low noise & microphonics) to keep in your emergency box.
Your power amp tubes are far more likely to be getting tired after a lot of hours under their belt. But that is a job best left to a tech, due to biasing considerations.

[frosty55]

Thanks.

[Sweetfinger]

I'll second the sentiment that your pre amp tubes are likely still in good shape. The only pre amp tubes that do need more frequent replacement are phase inverter and reverb driver tubes(if you have a tube driven reverb).