I replaced all the electrolytics except for the two large GE cans. Those things seem to hold up pretty well after all these years. Also, they're real pricey to replace, at least $20 each at the bare minimum. Not real pricey I guess, but way more than all the other cap's put together.
What I did was leave the two silver smaller can's in place, but inside the amp I disconnected them. The replacement cap's of the same values are SO much smaller than they used to be, so they all fit very nicely inside there. The only trick was the silver can closest to the front of the amp is actually a single and is for the negative supply. That cap's polarity was a bit confusing at first when looking at the amp because the + side goes to ground. Electrolytic polarity is CRITICAL because if you reverse them, they are like a dead short and things can fry real fast. Plus they can pop or at least smoke and ooze some nasty liquid.
Also, the 2 10uF cap's on the input board are for coupling audio, so I used poly film types instead of electrolytic since film is a far superior audio coupler. I didn't quite go to 10uF, but went 2.2uF instead. Still plenty of bandwidth there, and for Jerry style guitar, not an issue at all. I believe that some of the Mac's even used to use 2.2uF there instead of 10uF.
At first Tracy's Mc250 bench tested about 63 watts on one channel and 68 watts on the other. Kind of mushy and sluggish compared to what it should sound like. After this re-cap job, both channels were delivering a solid 82 watts per channel right at clipping. This particular Mc250 of Tracy's was by far the cleanest circuit I've seen in one yet. Outside had some metal pitting, but inside, I swear this amp had never been abused or even opened up before he got his hands on it. Every component was stock, zero charring around the Sentry Monitor resistors as we see in most used Mc250's. This baby came right back to life with tons of clean power. I love these amps.
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