I see them on the inputs too----which is odd because A) very difficult to get to and B) they are electrolytic when the SM specifies bipolar. Benign or should I replace?
I saw blue Panasonic's on the Mac I did and they appeared to be stock to me, they were date code correct for the manufacture of the amp which was like 1979...
Replace them ! Your there, there older then your children, replace them.... so splurge and spend maybe two bucks in a good way. It can't hurt anything to be thorough and complete since your already there and in neck deep:thmbsp:
I see your 5% film caps and they don't match original in my 2205 I worked on. This circuitry is feedback related, and has only high precision devices located near by it. I would tend to try and find the 2% original style parts from any manufacture and duplicate for both channels as best as possible. I have only seen 2% parts where your questioning, and the resistors near by connected are similar tolerances so I think Mac knew what they were doing and I would try my best to mimic Mac's original design just in this specific area... but this is my opinion and YMMV and others my disagree..........
The itty bitty blue caps behind the RCAs are bi-polar and WIMA 2.2ufd fits nicely there but you will likley have to de-solder the RCA connections to the board to access the board clearly on both side to replace the electrolytic, and then resolder the RCAs back to the mini board, after you clean and de-oxit it the RCAs themselves including the inner tip sleeve.. Be aware of the hard wiring trying to break off while you handling the board like this. You may end up reattaching a wire or two due to embrittlement of the aging cabling....Just reattach as needed with fresh solder and you should be golden...
I had to do all this because the entire assembly on the last 2205 I worked was covered in soot left by a Mac service centers hasty repairs, and the soot was shorting out the RCAs to ground when no creating a hugely bad contact situation, and just plain fugly to look at.
If your replacing your vintage RCAs then this should come out anyway just to ease your install of new RCAs. and while there I replaced the electrolytic's with WIMA's since they too are bi-polar and being a film type cap they should last you a lifetime. You can 0.1 bypass them also if you think a 1.0 to 2.2 ufd cap value is effecting your high end signal bandwidth. They serve one single purpose being there and that is to block any errant DC offset from your preamp output, or as techies like to say they provide AC coupling, while blocking DC voltages...tada !
Oh take a few snap of your work are before you disconnect anything then if a wire breaks off you will have fall back to figure out where it went... Love my cheap bench camera... saves me loads of headaches ....