I have a pair of 5210s, one for main amp the other is drives my talkbox (spare too if needed).  I added speaker jacks to the back of each of them - one for talkbox send and so I can optionally drive a Genz-Benz G-Flex George Lynch 2x12" cab (at 4 ohms).

I've had minor problems over the years (yes I bought one of these new in 1982) - they are very road amps but you must protect the knobs on these.  I have had to re-solder joints on the inputs and sends and some of the pots...bad solder joints, which have caused pops, hums and intermittent input signal.  Seems the knobs/jacks flex and the board does not so the damage is at those component interfaces.  I find them by carefully wiggling and prodding things with the head out of the casing and it on and playing (BE CAREFUL).  I have also had to blast inside the back of the pots with cleaner/lubricant.

I also found the jacks on the reverb tank leads are prone to being damaged and this can induce a nasty hum.  Cut the ends and resolder.  I like these amps live - the MG30DFX, MG50DFX don't have the same tone capability.

I do have a nasty pop in one of mine when I turn it off...likely a bad capacitor somewhere.  Anyone know?

Pooch