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Old 25th May 2008, 09:23 PM   #1
gorfeas is offline gorfeas  Spain
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Default McIntosh MA-6100 restoration

Hi there all,
I just got a nice present from a friend.....
Its a McIntosh pre-integrated amp MA-6100
It is however in a very bad condition.
He said he had tried using it but only one channel worked.
Before plugging in let me just ask something basic:

On the back panel it says 110V Ac input, however here in europe we have 220-230V. Can I make it work here?
what kind of conversion/re cabling does it take?
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Old 25th May 2008, 10:04 PM   #2
gorfeas is offline gorfeas  Spain
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sorry for so little info
they inlet is labeled:
120V
70-400W
50-60Hz
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Old 25th May 2008, 11:25 PM   #3
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Since it says 50/60hz you may use an autoformer to reduce the voltage to 120V.

Something like this is needed (500W):

http://www.action-electronics.com/trnsupdn.htm
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Old 26th May 2008, 08:17 AM   #4
gorfeas is offline gorfeas  Spain
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thanx djk
here are some fotos of the beast...
Click the image to open in full size.

all 4 fuses were blown...
should I use 250V fuses?
there was a 250V rating on 3 of them (i supose somebody tried to switch the originals) and a 6A rating on the one that looks the oldest.

Click the image to open in full size.
Click the image to open in full size.
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Old 26th May 2008, 08:31 AM   #5
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I don't have the manual for that one, but I think 6A is too big.

4A fuses will pass full power at 4 ohms, 125V or higher will do. AGC or MTH type fast blow.

The outputs are probably blown, use MJ15003 (only from an authorized distributor to avoid fakes). I can't remember what the drivers are. If any of the outputs have shorts from the base to either emitter or collector the drivers will need to be replaced too.

Use a 120V 75W lightbulb in series with one side of the line cord when you fire it up.
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Old 26th May 2008, 08:57 AM   #6
gorfeas is offline gorfeas  Spain
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I think you can find all of this info here under integrateed amp/ma-6100
I am afraid I am too ignorant to understand all of your advice.
What are the "drivers"?
Please do enlighten me...
thanx again
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Old 26th May 2008, 09:36 AM   #7
Spiny is offline Spiny  United Kingdom
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The 6100 Service manual suggests the power supply is 2 by 120 volt windings - these may have been rewired to make it run on 220v Inspect and see if its been modified.

If not its possible from the description and blown fuses that this was plugged into the european voltage

Check the powersupply rectifiers for open circuit, hopefully the fuses went first, then check all transistors for open circuit junctions replace as needed. Inspect electrolytics for bulges, splits and leaks replace any suspect ones. Check any voltage regulators. They may have failed and protected the main circuits.

Unmodified it should be powered via a 220 to 110 volt autotransformer and initially a light bub.

Modified - to the 220V line via a lightbulb.

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Old 26th May 2008, 11:04 PM   #8
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The schematic says the fuses are 5A.

Drivers are the transistors that drive the outputs (Q411, Q413 drive Q415, Q417). They are probably MJE243/253.

This is not likely to be an easy project unless you have experience.
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Old 5th July 2008, 07:38 PM   #9
gorfeas is offline gorfeas  Spain
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Default amp running

After all I have decided to take this to someone capable of doing the whole repair.
The people at Audio New Concepts were very friendly and helpful.
The amp is now in perfect running condition!
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