What JCM900 model is this ?

[ErikH]

What JCM900 model is this ?

There issome weirdness with the 900s, some have 5881s, some EL34s, as at the time the supply of reliable, good sounding el34s was very low.same reason Marshall sent 6550 equpped 800s to the states for the majority of its lifetime.

The general theory is the earliest 900s all had el34s and 5881s started to show up a year later. However my Dual Reverb head, the first my local shop got in after the amps were introduced had 5881s....one reason I hated that amp with a passion.

In addition to this, the MKIII came only with EL34's.

OP, if you snag it, take it to a tech for a checkup. Possibly have the filter caps changed. It's over 20 years old so it'll be due if they've never been changed.