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Old 6th November 2016, 11:02 PM   #1
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Default Problem with Mcintosh MC2200

Hey guys,

Can you share your thoughts with me on the following.

My Mc2200 sometimes, when I switch it on, the left channel remains muse. If I switch it off and on again everything is ok and both channel are working. Another thing, some times it looks like the same channel shows less power.


Any ideas what am I facing here?

Just for your info the amp has never been repaired so all the capacitors are original. Could this be the issue or the relay?

Regards
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Old 7th November 2016, 12:37 AM   #2
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That does sound like the protection relay. If there is an adequate replacement that can be made to fit easily, simply replace it, otherwise you'd have to open the old one and check whether it is still salvageable. In case anything more abrasive than some blotting paper soaked in contact cleaner is required, it's pretty much toast and complete failure only a matter of time.
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Old 7th November 2016, 11:12 PM   #3
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Probably the speaker relay, but also check the input sensitivity slide switch on the back, they get dirty.

On the 05 models with the meters, the ribbon cable in the front panel gets carbon tracks on its ends and the meters read funny.

Can be a great sounding amplifier, even close to 40 years old.

I have a mod list for the caps if you want to go through things, make it sound tighter in the bass, more detailed in the high-end.

(for MC502, 2120/2125/2200/2205)
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Old 8th November 2016, 09:55 PM   #4
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Hey Djk,



That would be great could you share it?
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Old 9th November 2016, 12:09 AM   #5
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This is what I do:

"Which caps are they DJK? I'll try them in my 2125."

Add one 47F across each 42V rail at the main filter caps

Add a 0.01F~0.1F film cap in parallel with C239, 240 (little board on the input jacks, very tight for space)

Add a 0.1F film in parallel with C203, 204 (input coupling cap to impedance buffer)

Add a 0.1F film in parallel with C207, 208 (output coupling cap from impedance buffer)

Add a 0.1F film in parallel with C219, 220 (feedback cap)

Add a 0.1F film in parallel with Q215, 216 (bias transistor)

Add a 0.1F film in parallel with C305, 306 (15V regulator outputs)

Add a 0.1F film in parallel with D304, 305 (reference diodes for regulators)

I cut off all the push on connectors in the power supply and speaker relay and soldered them direct. I soldered a pair of 0.1F film across the speaker relay contacts and cleaned the relay contacts with a sheet of paper and applied De-oxit.

I sprayed De-oxit on the RCA jacks, cleaned the input sensitivity selector switch (very important), and the edge connectors for the L and R amp boards.

I removed the 10-32 screws on the main filter caps and used De-oxit before replacing.

Do not move the chassis with the bottom off, the glass could crack. Put it on a small piece of carpet to help turn at different angles.

The 47F are under a lot of stress, I used 100V caps even though they only run at 42V.

Even though this changes no measurable performance specification, it will change the sound more than you can believe.

Jackhammer bass from an amp with a DF of only 14?

************************************************** **********
You should just be able to jump across the input caps and sensitivity switch with no problems there.

If you're trying to use better input jacks the grounding and the 0.01F caps to ground become important. If you try and eliminate the input attenuator you will probably need a cap to ground from the node of R201 and C203 on the driver card, somewhere between 10pF~100pF.

Good luck.
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Old 9th November 2016, 12:11 AM   #6
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Its the digital volume control chip. Change out to a pga2311.

When the fault occurs spray the chip with freeze spray to see if it changes.
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Old 9th November 2016, 12:14 AM   #7
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"Its the digital volume control chip. "

Click the image to open in full size.
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Old 9th November 2016, 06:09 AM   #8
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Lol I was reading topics on the main page and thought I read C2200 sorry for the confusion.


Totally wrong subforum to boot! The C2200 is a tube preamp and would be in the tubes/valves section. I need sleep
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Old 5th December 2016, 11:51 AM   #9
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So cleaning the relay didn't solve the issue. So I'll be ordering a KUP-14D15-48 online...for 35 euro !!!!! autch!
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Old Yesterday, 01:22 PM   #10
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Hey Guys,

I've just install the new relay...and.... the same. Once and a while one channel drops!!!!

But I've noticed something else when I'm about switch off when turning slightly the on/off switch the drop channel comes back again!!!!!

Really strange

Can any one help on this?
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