Memphis MCD1000 driver board - diyAudio
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Old 29th September 2011, 02:27 AM   #1
Dr Zeus is offline Dr Zeus  United States
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Default Memphis MCD1000 driver board

I've got another one of these with bad outputs and failures in the driver board. This amp is very similar to the chrome/fin version, only slightly newer using a case like the Memphis Belle:

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In these photos, the top driver board is OK. In the photo of the main pcb, all outputs on one side were internally shorted so they've been removed. The amp powers and might play with the one good driver board plus the 'bottom' side outputs.

The bad driver board (bottom) has several shorted components:

D841 12v Zener 1n4742 measures 11ohms in both directions
D851 12v Zener 1n4742 is measuring a bit low (0.580) whereas the zeners on the good driver board are measuring 0.650
Q852 and Q854 driver transistors labeled A1023 shorted emitter to base
Q842 and Q844 driver transistors labeled A1023 shorted collector to base
R842 is measureing open and should be only 1 ohm

I do not have any stock of A1023. Can I use BD140 correctly oriented?
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Old 29th September 2011, 02:36 AM   #2
Dr Zeus is offline Dr Zeus  United States
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I should mention this amp may have died from beer. No, not alcohol poising; the amp took a beer-bath years ago. Surprisingly the amp looks alright cosmetically.
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Old 29th September 2011, 02:42 AM   #3
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I found the KSA1013YBU very close to the 1023 and the compliment KSC2383YBU for the 1027. These are T0-92L package.

cory
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Old 29th September 2011, 07:03 AM   #4
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The BD140 may work but the other one that was suggested may be a better match.
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Old 29th September 2011, 08:12 AM   #5
amc32 is offline amc32  United States
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Got to tell say, these are my favorite amp to repair. Common problems driver cards simply unplug. Whenever you find them broke buy them. Rebuild whatever cards that need to be rebuilt and store the cards in stock. These amps can be repaired quicker than they can be torn apart.wished Memphis wouldn't have discontinued the use of circuit desighn. But for what its worth let the customer know that the amp is labled, for 2 ohm operation not 1 ohm like the previous models. Though I don't see why it won't handle 1 ohm. But it might save you a future repair.
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Old 29th September 2011, 08:17 AM   #6
amc32 is offline amc32  United States
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Be sure to check the 1r0 current limiting resistors on the output driver cards
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Old 6th October 2011, 06:27 PM   #7
Dr Zeus is offline Dr Zeus  United States
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Where can I source replacement 1r0 resistors?
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Old 6th October 2011, 06:59 PM   #8
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Digi-key, mouser...
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