Getting into the MC 2505
 

One of the guys brought up "Vintage Gear" and mentioned the MC 2505. Since I have some time while the other amp sits waiting for parts, I've decided to dig into the 2505 which still works BTW, it just doesn't sound good!!

The electronics are an interesting example of U.S. technology in the '60s along with the Space Program and the Boeing 727 jetliner, etc. So here are some photos. In just 2 or 3 hours, I've polished it up nicely and changed out almost 20 of the old and cruddy screws.

http://home.comcast.net/~mc_audio/MC2505_panel_off.jpg


http://home.comcast.net/~mc_audio/MC2505_rear.jpg


http://home.comcast.net/~mc_audio/MC2505_top_board.jpg


http://home.comcast.net/~mc_audio/MC2505_rectifiers.jpg


http://home.comcast.net/~mc_audio/MC...iltercap_A.jpg


http://home.comcast.net/~mc_audio/MC2505_NP_caps.jpg


http://home.comcast.net/~mc_audio/MC2505_640_caps.jpg


http://home.comcast.net/~mc_audio/MC2505_driver_A.jpg


http://home.comcast.net/~mc_audio/MC2505_screws_B.jpg


http://home.comcast.net/~mc_audio/MC2505_speakers.jpg
Many of the screws will need to be replaced.


As stated.. it's a nice specimen of American electronics, but it simply sounds flat and cardboard-like. The obvious first cut diagnosis is to re-cap, but some of those ganged power supply capacitors are NLA (not available) and other axial lead caps look a bit strange.

What are those components that look like pieces of candy in a yellow, red and white wrapper?


-Gregory

Gregory,
Great pictures. The first one makes it look pristine, and then your close-ups are a revelation! I'm not a vintage guy at all, but would love to some day have something like that as a project. For a ~40 year old piece of equipment to still be working it's a testament to the workmanship for which Mac is famous.

Gregory,
Nice pics, and this looks like another good project.
Maybe Terry DeWick can point you to a place to get the Power Supply CAPs, or some replacement that will work in place of exact replacements.

You do very nice work, and deserve to build your self a real nice workbench, so you can get out of the kitchen.

I look forward to more of your posts.

Well thanks.. the forum will allow only 10 inserted pics so four or five had to be cut. Here is a view of the MC 2505 with just the meter top-cover removed.

http://home.comcast.net/~mc_audio/MC2505_cover_off.jpg

Some who have come over and seen it powered-up in past years have done a double-take checking it out. Sitting there it looks really sharp, but a close inspection reveals that it's in need of some TLC. If you're a `detail´ kind of person, it it can be very satisfying.

-Gregory

WHAT!! the water cooler is in there, and what if I want to get a quick sandwich or raid the fridge? :D

-Gregory

Add that to your workshop - One refrigerator, One Water Cooler, 10,000 tools. :banana::D

So where do we start? Murray says some guys re-stuff the ganged filter caps with axials or radials, and others just leave them in place and attach caps under the chassis. This might be too much like stepping into Terry's realm. What's available for axial Muse and KZ electrolytics? Maybe check out HME? Where can I order a pair of replacement 9300uF cans with date code: week 49 of 1972?

Also the drive boards are Mc part #043-916 which calls for Service manual 039-016. My service manual is for the earliest 2505 and is substantially different.

-Gregory


p.s. I think it's ok to change any screws on a McIntosh with new ones, but messing with the knobs and end-caps is a no-no.

The MC2505 is such a great little amp--nice photos and write-up.

I'd like to take it down so the four heat sinks are off the chassis, and the two driver boards are out for a good decrudding and degriming, but cannot think of a good way to do it. All of the final transistor wires would need to come off the driver boards (there are solder sleeves) and the two green and two red power supply wires would have to come off. Here are some pics:

http://home.comcast.net/~mc_audio/MC...atsinks_II.jpg
View of the four heat sink assemblies.


http://home.comcast.net/~mc_audio/MC...inal_wires.jpg
Wires from driver boards to transistors on heat sink. Note the two red power supply wires coming in from the left.


So it's something to ponder. Where to desolder? It will be fun and satisfying to rebuild (reassemble) the final amplifier stages after everything is deoxidized, defluxed recapped and restored.


-Gregory

You can also loosen the caps and transformers on the chassis and polish under them (complete chrome restoration!).