McIntosh - Hints and Kinks

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dr*audio said:
It appeared that the front panel has to be removed for the bottom to come off. Am I right?
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Do be careful with that glass faceplate. I'm waiting for delivery of one to Terry for my MC2105. Not sure about the rest of McIntosh production, but the glass faceplate line seems to stay quite busy and lead-times are substantial.
 
Whenever I have taken an MC2105 apart, I usually remove the knobs and glass first, before I start digging into that beast!
 
Thanks guys! The glass is already broken, the customer has a replacement. Might as well take it off.
 
Ok this is really weird. Only two output transistors, Q242 and Q235 have silpads. Only the negative rail is being shorted to ground, probably the paint on the heatsinks is providing some insulation. It is obvious someone has been in here, but why remove almost all the silpads? Secondly, the yutz who worked on this amp replaced one of the 39,000uF / 50V caps with a 40V cap. The other one leaked, so now both need replaced. I have an e-mail into McIntosh parts asking about the caps. Mouser and Digikey don't have anything that will fit. Anyone have a line on these?
 
There are a couple at Mouser. Look for Sprague 41000µf/50v. These have no insulators around the connecting lugs so take care installing them. Blue sleeve.

The other one is a Mallory, I think, and has an insulated lug, I believe.

Murray
 
Mr 74 Clean/ Lube points on station selector gang

Terry quick question,

I have a Mr74 tuner that has sat a while. I want to know if the tuner gang (the thing at the end of the tuner knob shaft with fins that rotates for station selection) has any clean or lube contact points and what kind of deoxit do you use? I have the multi Survival kit with multiple choices. Also a pic illustrating the points to lube/ clean would be helpful. Any special precautions I need be aware of ? I assume after clean/ lube you would rotate the knob all the way up and down the dial range several times, correct?

No real issues, just want to cover the base.

Thanks in advance,

007
 
Have been using DeOxit F5 on the ground wipers with very good success, usually follow up with quality turbine oil for a longer lasting lube.
 
variac?

I am new to Mac tube amps and have recently acquired a MC275ce. Don't know if I need to power up with a variac to protect the components. I heard that you can use a light bulb inline of the power cord on initial powering to have nearly the same protection the variac offers. Has anyone else tried this method? thanks.
 
dewickt said:
Have been using DeOxit F5 on the ground wipers with very good success, usually follow up with quality turbine oil for a longer lasting lube.
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What is Turbine oil (parson my ignorance)?

It looks like everything in the survival kit is for clean AND LUBE. THE LUBE PART BEING BAD ...

Thanks,
Phil
 
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midlife said:
I am new to Mac tube amps and have recently acquired a MC275ce. Don't know if I need to power up with a variac to protect the components. I heard that you can use a light bulb inline of the power cord on initial powering to have nearly the same protection the variac offers. Has anyone else tried this method? thanks.
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Yes, however I believe Variacs can be readly had on the 'Bay and rather inexpensively ..round 50 bucks + shipping. The lighbulb method is fine, but isnt as convenient as you power up your component. I feel the variac is safer, IMHO, and informative, having a volt and ammeter to watch what your feeding your tube amp as you go and where, if any problems begin to occur .

You can charge the capacitors slowly using the variac and increase the voltage slowly instead of a sudden inrush of voltage/ current which is better for a capacitor or component that has sat unused for a while, again IMHO.
 
First - Turbine oil is a high grade light oil, the type commonly used in the long spout oilers 'Holdens Zoom Spout' found at most hardware stores.
Second - the 275CE is new enough (1998) to not have to need a variac, to ease fears turn on for a minute and off for 5 minutes, a few cycles like this should be all you need to reform the filters.
 
dewickt said:
First - Turbine oil is a high grade light oil, the type commonly used in the long spout oilers 'Holdens Zoom Spout' found at most hardware stores.
Second - the 275CE is new enough (1998) to not have to need a variac, to ease fears turn on for a minute and off for 5 minutes, a few cycles like this should be all you need to reform the filters.
Click to expand...

Following the above recommendations should it also be connected to speakers and patched to a preamp? Tubes in place? Any particular input mv settings? thanks.
 
The speakers and source are not necessary, but then you should be able to listen to it after the cycles to ensure everything else is OK.
Never fire up a tube amplifier with it's tubes not in place, a few of the small tubes may be OK but you want the outputs in place to properly load the power supply and not have the voltage soar to way above normal.
 
Bridging MC-2000

To Mac lovers,

A quick Q. I have a pair of MC-2000's and trying to mono bridge them. I know MC2102 & MC275 have this function, but can MC2000 be bridged without significantly altering the circuit and no damage to speakers? Any thoughts on this (ie, benefit versus cost) I am using one and but don't have the use for the other and don't want to sell it either...
 
Best way to find out is from the factory customer service 800-536-6576, sorry I do not have an answer to this one, it is best answered by an expert in newer equipment.
 
Hope this will be of some help to all you rebuilders out there...

Here is an image (directly from the McIntosh instruction manual) of the schematic for my early-version MC-30... this is probably pretty close, but not necessarily identical to, the 1955 SAM'S guide that I see floating around.

As you can see, the serial numbers covered are 10095 and above, and the date of the schematic is 10-16-54.

( EDIT: I see the AK server shrank the image a bit-- if anyone needs a larger, clearer copy, you can find it at:
http://www.kinescopes.com/mc30.jpg )

-Kevin
 

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I have a MC275V that I purchased from an authorized dealer in Oct 2009. I use it single ended direct from my CD Players variable output.

I have purchased 3 NOS Sylvania 5751 TMB to roll the AX7A's & 4 Mullard CV4024's to roll the AT7's. This combination has worked from Oct until 2 weeks ago.

During the last 2 weeks I have noticed a sound I think of as leaky caps, dirty potentiometer, snaps crackles & pops for 3 to 5 seconds on shutdown.

I have removed the CD feed and still the problem persists.

I have replaced V1 5751 with the stock AX7A and the problem persists

I have replaced the CV4024 with the stock AT7's and the problem persists.

I have replaced the V1, V2 & V5 5751's w/stock AX7A's and the problem is diminished yet not resolved w/my ear to both woofers of my Rogers 3/5a's I still hear faint snaps, crackles & pops.

Any thoughts?
 
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