CurtPalme.com Home Theater Forum

[Jeremy112]

Thought I would share this project because its an interesting item. This is a McIntosh MI-3 Maximum Performance Indicator Oscilloscope. It is supposed to help one with fine adjusting of FM reception to get better signal deviation & quality from FM. It can also be used as a scope, or as I call it "Vintage Media Visualizer."

This particular scope was in pretty rough shape when I bought it. Surprisingly, when I first turned it on it worked, but I had a hell of a time adjusting the wave on the CRT because the controls were so bad. Either way, it was quite impressive to see it work considering the inside, and outside were caked with layers of filth and there were enough dead bugs jingling around inside of it to make a musical instrument.

I finally got around to it this week since I just finished up the receiver many of you saw in the buy & sell here. Since starting, I have managed to get all the pots deoxed & lubricated, which made the biggest electronic difference in the unit. Completely disassembled the entire unit to clean all the wires, tubes, black chassis as well as the tube chassis (as much as I could since there is lettering on the tube chassis & the rust on it was near and on some of the lettering). I cleaned the CRT up & readjusted the astig (yes, this little guy actually has astig, which is more than some CRT PJs can say!) as well as the static position adjustment. I also repaired the black paint on the glass panel as a lot of it had bubbled and peeled off from the glass face. Aluminum knobs all cleaned up as well.

I didn't bother replacing any capacitors in this unit since the few that are in here read fine, and the ones inside that you cannot see in the photos are mylars which checked out perfectly.

All but 2 of the tubes are the original "Made for McIntosh by RCA" tubes, the replacements that are in it are RCAs, but I guess I can't complain since I have 5 of the 7 original tubes anyway, and at least the replacements are the same brand as the originals

The one thing I have been wondering is, because you input sound into it, I am wondering if the sound that you output from it sounds any different because of the tubes? I haven't spent much time testing this out, but it wouldn't surprise me if it affected the sound a bit since it has to be in the signal path if you want to use it, and because its transistor free

Anyway, all that's left is to refinish the top and bottom covers, and new gold plated RCA jacks, which I have ordered the same ones that McIntosh used on my MC2102, as these are very similar to the old ones for internal connections, and they are extremely high quality. As for the rusted tube chassis, I hope to find one of these for parts that has a nice tube chassis so I can swap it out. Afterwards, it should be a 9.5 out of 10 unit.

For now, heres the part everyones waiting for, these are pics of its current state of restoration, almost done, just needs what I mentioned right above done to it and it will be complete. Enjoy the pics!

[ecrabb]

Holy crap, that is awesome.

SC

[Curt Palme]

And it deserves a YOU SUCK!

Keep these pix coming, even if your restoration item is a bit more mundane. This is heavy porn for a few people here.

[Curt Palme]

And it deserves a YOU SUCK!

Keep these pix coming, even if your restoration item is a bit more mundane. This is heavy porn for a few people here.

[CIR Engineering]

Wow, I would love to have that in my rack. What a cool piece. Where did you find it?

craigr

[Jeremy112]

I picked this up late last October from an estate sale on the outskirts of town here. When I was told about this sale (I got to get first dibs on everything!) I really wasn't expecting it to be any better than the last one which was a bunch of radios, and I mean a LOT of radios (over 100, and 60 or so were tube, they are all gone to new homes now )

Well... when I got there, the first room I step into has a bunch of McIntosh. Enough that I was questioning if I could afford this place

Anyway, after spending over $6,000 I wound up with about 4 or 5 pick up truck loads of amps, speakers, receivers, preamps, tuners, R2R, cables, DVD players, some fairly high end VHS machines etc...

This piece was actually the cheapest thing I bought for a component. The 3 or 4 pairs of AR-3As I picked up for less than $50 for all of them, and only one pair was in really rough shape.

As for this scope, it was nice $75 find, and I at first debated it even though it was McIntosh, just because it was in such horrible condition. I am now, however, very very glad I took it since it really is quite a neat piece.

Once I get it finished, I'll get some pics of it with the matching MA 6100 amp/preamp I have.

[Boilermaker]

Wow! You definitely suck. I have been looking on fleabay for one for a long time. They always bring over $1k.
Don't worry about it affecting the sound. Look at the schematic and you can see that the input probably has between a 500K and 1M ohm resistor which will be an insignificant load on your preamp.
BTW, I just finished a Restomod project of an MX110. I took many pics and will share when I get time.

[Jeremy112]

Thanks for the "You suck", Boiler When I looked it up on ebay after I bought it, I pretty much stared in shock at the value of the scope, but then again its quite rare, and as all of you can agree, its pretty damn cool

Glad to hear it wont interfere with sound. I've been thinking about getting a McIntosh tube FM tuner for the little vintage set as well, never had a tuner driven by tubes, so its definitely on the list.

I wil have to put the scope with the rest of the mac stuff & take some photos, all that blue/bluishgreen looks quite pleasing in the dark. Especially with tube stuff

[Boilermaker]

You can't go wrong with an old Mac tube tuner. I just finished restoring a 1960 MX-110 tuner/preamp where I replaced every component with modern high quality devices. I even used custom blue LED's to replace the old incandescent festoon bulbs that used a blue gel. It looks real cool. If I can get the pictures loaded, I'll post them.

Bob

[Jeremy112]

[jask]

more pic??

[Jeremy112]

Sorry Jask, I didn't see your reply! I've been pretty busy, but I will try to get some more pics of both the MA 6100 and MI-3 this week.