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McIntosh MA6100 Power Supply


John Warren

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This was a cool project.  Gent purchases an MA6100 from an estate sale.  The amp is new, never used, still wrapped in plastic bag but it's missing the power supply board.  So he needs a board and contacts me.  I do not have these boards just lying around.  There's two ways to solve this, buy a "donor" amplifier and hope it has a good board or design a new one.    When he sent me an email, I intially said I wasn't interested.  We chatted a bit more and I decided to do it and, as it turns out, wasn't really that difficult.

 

Since I too own a 6100 I decided to design a board for my unit and his. 

 

So here's the factory original:

factory_1.thumb.jpg.b4ffa9e96c55aeaa0c86cdfef7fd6dbe.jpg

 

And the replacement:

PC_board_6.thumb.jpg.447b134f0869b514fd1a3a2f17f801f6.jpg

 

Board pulled from the amplifier:

PC_board_0.thumb.jpg.c493ec9280853db4e3dc1f9c8b661f7a.jpg

 

Board ready for install:

 

PC_board_5.thumb.jpg.85cb060d792eec4be25580a4518427c9.jpg

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Thank you.

 

On the difficulty scale this board is a fairly straightforward effort.  I also have a few design tools that help in identifying trouble spots before I commit funds to board production.  I do have a second iteration of the board designed but will wait until I have another 6100 in for service before ordering it.   

 

One more photo of the installation:

PC_board_9.thumb.jpg.07c2b09c25d7042d4ea62884369dcb90.jpg

 

 

PC_board_8.jpg

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21 hours ago, henry4841 said:

Nice having you as a member here. 

Awesome, thanks!

 

Next questions, how can this relatively simple design be improved?  There are a few modifications that can be made but there's also space constraints.  That requires going to the simulator.  Will detail that on the forum below.

 

MA6100 Power Supply Board (northreadingeng.com)

 

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1 hour ago, John Warren said:

Awesome, thanks!

 

Next questions, how can this relatively simple design be improved?  There are a few modifications that can be made but there's also space constraints.  That requires going to the simulator.  Will detail that on the forum below.

 

MA6100 Power Supply Board (northreadingeng.com)

 

Not everyone here frequents technical sites so share what you find here on a social forum as well. I am sure there is interest among electronic novices like myself. 

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  • 2 weeks later...

Here's the revised design (R1.1).  A bit tidier.  The caps can be ceramic disk of film type.  Caps across rectifiers should be either ceramic disk or polypropylene.  I kept the ceramic disks because I have them.  If they're film, the must be polypropylene given the application.  It's a significantly better dielectric than polyester, far better insulation and dielectric behavior.  The board will accommodate a WIMA PCM5 AC pulse type.  For the output stage RC filter a WIMA general purpose polyester (PET) is ok and what's installed.  It's also in the PCM5/7.5mm package replacing the ceramic disk (easier to install and I have them).  Polyester caps are fine for decoupling and noise suppression and they're low cost.  They pick up moisture and that changes the behavior as a function of frequency.  They have rates about 40X higher than polypropylene.   As a general rule you can replace polyester with polypropylene but not the other way around.

 

PC_board_R1.1._2.thumb.jpg.fab99f1f2479685c05444b4a57db2cbd.jpg

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" The caps can be ceramic disk of film type"

 

Was not aware such existed. Learn something new everyday. Unless a circuit is very critical I have no problem with a polyester cap even replacing a polypropylene. Dielectric absorption is better with a polypropylene but in most circuits it does not matter. 

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On 3/26/2023 at 7:31 AM, henry4841 said:

Dielectric absorption is better with a polypropylene but in most circuits it does not matter. 

Capacitance changes with changes in frequency, voltage, humidity and temperature between the two "film" types are significant. 

 

Companies like WIMA, KEMET, Vishay and many others have factories dedicated to the fabrication of either polyester or polypropylene film caps.  There's manuals, application and usage guidelines specific to each type.  The selection of the wrong film in many applications (power supplies as one example) will determine the failure rate.  The point being, it really does matter.

 

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