McIntosh Amps Out Of Storage

Hi All

I have come into ownership of three McIntosh Amps. They are (2) MC-30s and a MC-240. They're in fair condition. They came to me indirectly from someone who died at least 12 years ago. They have been in semi-protected storage since that time. They have not been powered on at all in the period since the original owner died - perhaps before then.

I want to make these work so I can decide which to keep and which to sell. I have a very limited electronics background, but I'm studying and learning as I can find information. One thing I am concerned about is applying power to these amps and blowing all the electrolytic caps out of them. It is my understanding that I must slowly bring up the voltage through a variac to restore the caps before applying full power.

I need help in understanding what the proper precautions and processes are that must be followed to safely bring these amps back on line. Anybody that can offer help or suggestions - your input would be greatly appreciated.

Bob

bobkos at earthlink dot net

Reply to
Bob Kos
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That is recommended. If it's been only 12 years and they haven't been in extreme temperatures, that may not be necessary.

If you don't have a Variac, there's another way. Go to the hardware store and build an apparatus that lets you put a light bulb in series with the "hot" (black) wire from the AC line. Get a set of light bulbs of various wattages (25, 50, 100). Apply power first through the 25-watt bulb; wait a few minutes; power down and put in the 50-watt; and so on. It doesn't matter whether the bulbs light (and not having done this myself, I'm not quite sure whether they will). Their purpose is to limit current.

Reply to
mc

Powering via a variac is not a bad idea, and I would, just because I have one. However, the trick to this is that they are manually switched ie the power switch physically switches on power to the main power transformer. If these amps are electronically switched ie the power switch physically switches power to a small standby transformer, and then a momentary push button takes them out of standby, OR power is always applied to a standby transformer, and a momentary push button takes them out of standby, then they will not work with a variac, or any other form of serious current limiting in the primary.

The reason for this is that the standby supply will not reach sufficient level to work the power switching circuitry, until you're at 60% or more of normal input. By this point, when it does come on, the main supply rails will be high enough to do the damage, if there's going to be any.

Probably, they will be physically switched, in which case you will be ok, but also bear in mind that if they have relay based output protection, you will not get any output from the speaker terminals, until the supplies have reached sufficient levels for the relay driver/ fault detector circuits to operate.

I doubt that any electrolytic reforming will be necessary with this age of component. The only thing that you might get, is a blown fuse at first powerup, due to the fact that they will be old 'tired' ( metal fatigued ) fuses in there, and that there will possibly be a very large input surge current first time on.

Arfa

Reply to
Arfa Daily

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Let me ask this. EVB had a special deal last month on their Parker design ESR meter. I grabbed one. Will this meter help me if the caps have degraded? Will it be useful in monitoring the reforming progress - or tell me if they're even bad before I start the reforming process?

Reply to
Bob Kos

Yes, absolutely. It is a very sensitive demonstration of re-forming.

Frankly, with a 12-year-old amplifier, I would just turn it on, watching carefully for the first few seconds just in case a capacitor overheats. It's very unlikely that they will need any special care if it's only been 12 years.

Reply to
mc

Except they were already old when put in storage.

Mark Z.

Reply to
Mark D. Zacharias

Whoo, these are old!

The MC-30's are circa 1954-1962, listed for $153 and may be worth from $385-$1381 each.

The 240 is circa 1960-1969, listed for $288 and might get from $611-$3000.

(Why do I feel like I'm on "Antiques Roadshow"?)

I worked on some McIntosh stuff in the 70's. I think I got a hernia lifting one of them onto my workbench one day. Built like tanks, point-to-point hand wiring. Massive.

Cheers

Reply to
Mr. Land

Thanks to all for your helpful advice. I'll ring back as I make progress with these amps.

Reply to
Bob Kos

Reply to
carneyke

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