Thanks for helping me choose one guys. Since there are kits you can buy on Ebay with quality Nichicon (Japan) caps and detailed instructions, is there any reason I should sent a heavy amp into a professional for refurbing?
There is a lot to unpack here but I will try........
Refurbishing is a good idea to do yourself IF, you have the skill set, experience and the proper tools. You also need the proper test equipment (and operational knowledge of how to use it) if something goes wrong (Murphy's Law). The "kits" and "detailed instructions" you'll find on eBay are problematic. Do some research here on AK for the eBay sellers names.
I agree in large part with
@ramjet - don’t depend on a kit. Doing a quick search on the 2105, looks like there’s a 4-5 PCB’s with ~12 smaller discrete caps, 2 big power supply caps, and a multi-can cap.
If you have good soldering experience, download a service manual and search for internal pics to give you an idea of what’s involved. If it looks very straightforward, you can *consider* doing it yourself, but IMO, if you need detailed instructions to make sense of it, it’s not a good idea to take it on yourself.
There’s not a lot of caps, but even if you have good soldering skills, you need to have confidence you can get to the boards. A couple look to be plug in’s, so those are probably not bad. Some look to have a bunch of wires attached, so the question is whether you can replace the caps either a) without removing the wires, b) feel confident you can remove the wires, keep track of where they go, and can put them back correctly. If the wire pull off, it may not be bad. If you have to desolder them and resolder them, again, you should feel very confident in that.
Need to also think about how you’re going to handle the can cap too (4 caps in one can) - will you get a new can cap from a place like Hayseed Hamfest, will you take out the old one and re-stuff it with discrete caps, or will you use discrete caps under chassis (I.e. use discrete caps, without trying to fit them into the old can). For the two big power supply caps, you likely need to know the allowable size range, lead/screw spacing, what’s insulated on the OEM caps, etc. You can’t just get any big caps with the same uF and voltage specs and expect they will be plug and play.
There’s also some references to a runaway thermal condition that you might want to make some mods to prevent.
I’m all for people doing as much as they’re comfortable with to save $$. I do that myself, realizing that while, all things being equal, it would be better to have an experienced tech run a lot of tests with distortion analyzers and other test gear to give it a stamp of approval. But, nevertheless, I choose to do the work myself esp if I’m starting with a piece with no known issues except old caps and take the risk of not doing a bunch of bench tests afterwards. Because I can do the actual work myself, which saves hundreds of $.
BUT, I wouldn’t recommend anyone use a McIntosh as a first project or hope they can get through it without having a concrete plan of exactly what they’re going to do and how they’re going to do it. The downsides are too high, and there’s a real risk of taking a working piece of gear with old caps and damaging it and having to go to a tech to try and recover it from the dead.
One way I would think about this is: If you’re getting this for free, even if you spend a few hundred $ to have it done right by someone with experience, you should still come out well ahead. If the cosmetics of the amp are very good and it’s fully restored and made robust against any possible danger issues like thermal runaway, it should be a $1500+ amp no problem. So, say, $200-400 to get to that point is pretty cheap.
Just be sure, if you go down that path, that you’re picking a proven, reliable tech that you don’t have to worry about doing shoddy work or messing up your amp.
