Shep,its been a while since I've been in a MKIV but if I remember correctly,it has 2X 220uf/300v stacked,and 3 or possibly 4 30uf/500v,pretty much the same as most MK's.You are going to have to look inside first as there are a few more lower voltage caps associated with the bias and EQ supplies.
Kdove,if your caps are original,I would say its time.I have seen posts here and elsewhere where people say"my amp was just at Mesa for a tune-up and they didnt change them".I personally dont buy into that.I had a guy ,who,happened to be the last parts supplier down in lower Manhattan in what was known as "Radio Row",he was also a designer for RCA back in the '40's and '50's,so he knows what hes talking about,tell me that manufacturers only recomend a 10 year shelf life for electrolytics.I actually saw him throw out boxes of them when he closed up in the '90's.He actually gave me a couple of boxes of fresh ones so I wouldnt think about taking the older ones out of the garbage.And believe me this guy was tighter than a bulls *** in fly season,so if he thought he could get away with selling them off he would have.That along with seeing what can happen when a cap explodes,convinced me.It is possible your caps may last,but I will never take that chance.
Kdove,if your caps are original,I would say its time.I have seen posts here and elsewhere where people say"my amp was just at Mesa for a tune-up and they didnt change them".I personally dont buy into that.I had a guy ,who,happened to be the last parts supplier down in lower Manhattan in what was known as "Radio Row",he was also a designer for RCA back in the '40's and '50's,so he knows what hes talking about,tell me that manufacturers only recomend a 10 year shelf life for electrolytics.I actually saw him throw out boxes of them when he closed up in the '90's.He actually gave me a couple of boxes of fresh ones so I wouldnt think about taking the older ones out of the garbage.And believe me this guy was tighter than a bulls *** in fly season,so if he thought he could get away with selling them off he would have.That along with seeing what can happen when a cap explodes,convinced me.It is possible your caps may last,but I will never take that chance.