I picked up a pair of Gibson non-working amps 1972 G-40 and 1971 G-70. Yeah. I think I overpaid and they don't work, which I knew they didn't work when I got them. I'm hoping the problem is 'simple' but wanted some advice before I get carried away. All they do is Hum. Guy I bought them from thought they needed re-capping and I thought the same but could be other things too, a gamble. I opened the cases up this afternoon and see that the power capacitors all have bulges on the end(s) and discoloration on the bulges. Candidates for replacement. There is corrosion on many of the steel fasteners (since steel screws and such were used to attach to aluminum which makes steel corrode faster - probably some bad grounds in there somewhere). Before I try the "local" electronics parts store for new caps that will perform for years ahead .. do I need to worry about seeking out vintage NOS caps (that are probably pricy)? Or just tie a bag of the original caps inside the case for any future owner? The G-40 has a mystery speaker that I attached a picture of. An obvious replacement due to some wire soldering at the speaker. Might be a 'blackback Celestion' but guessing since pictures I found on the net don't have the frame stamped rib darts. The G-70 has the factory Gibson speakers with labels. Bad appearing caps on the G40 are the three large blue 400uF-400V on the lower left of the PC board as pictured. Bad appearing caps on the G70 are the two large blue caps also on the lower left of the PC board as pictured. The two large vertically mounted caps seem ok from appearance. There are a couple of bad pots on the control panel but I'll worry about those if the rest will work again. Same with the frayed power cord on the G40, planning a 3-prong plug on both amps for secure case grounds. Thanks in advance for any notes/thoughts/ideas as I get into this.