Hey A, good to see you posting
, vans's advice is a good start. If you need parts MJMP's (our master tech) site is a good source (http://www.marshalljmpmodshop.net/index.htm).Take your time with the various boards and threads, we have accumulated quite a bit of info etc over the years but it's laid out reasonably logically, read the various bits as you need to.First (if you haven't already) download the manual and read it. Then load the factory presets. If the battery is dead (and probably is) the programs are lost after power off (so probably the next thing to do).
Does your unit have a top switch to change the output from inst to line level ? If so the rear (input) jack mod is worth doing (MJMP has all you need for this mostly pre-wired).Battery mod is a must do, or you will loose any program changes when you turn it off
Noise mod(s) deals with quite a few caps that need changing, the noise (from old caps) is most apparent at high gain settings.
Transformer wise you could go with a MDRT or someone may have a spare original 240v tranny. MJMP gets the MDRTs made from time to time, seems he has some stock at the moment, this will change the sound a bit (plenty of posts about it).The tubes will need changing, lots of posts about tubes, very subjective area as they all sound different, e.g. I changed some Groove Tube 12AX7s for some nice new New Sensor Mullard 12AX7 long plates the other day and they sound sooo much better. The GTs were very harsh sounding....If you can, run the unit in stereo with stereo power amp and 2 cabs, it sounds much better than mono (not that it sounds bad in mono)When you switch it on it will display the EPROM (firm wear) version. e.g. 1.38, or 2.00, or 2.01 (it's also written on top of the EPROM (front right hand side as you look down with top off)). MJMP has the 2.01 EPROM (which is the last revision ADA made, includes being able to save and load patches to PC via midi port). The factory patches are on the EPROM (later versions included additional patches) so you can load them anytime even with a dead battery.As you have already discovered, unused/un-programmed patches default to 0 until you change and store them.Again, welcome to the forum, lots of people here who are happy to help