My MA6200 Challenge

shelly_d

shelly_d

Not An Audiophool
I bought my first Mac on that auction site. A distressed MA6200. The initial issue (I hoe the only one) is that the former owner removed the Tape Mon, Tape Dub, Speaker selector, power push buttons. I knew this going in. After I received it I found that the circuit board that they attached to was gone as well. So far its noting I did not expect. The seller was up front about the switches and I was hoping the circuit board was inside the amp but not really surprised it wasn't. My plan is a new DIY circuit board with replacement switches with a DIY mounting system. All of it I believe is doable. Will have to sacrifice the lockouts that the two dubbing and two monitor switches share but that deficiency is worth it to get this back in service.

Here are two pics of the inside of the amp where the circuit board went. I have removed the led indicator board to give myself a little more work room.

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attachment.php


The help I need now is to get an image of a stock installation so that I can get some feel for the orientation of the switches and board in the amp so that I can lay out the board in Eagle in a way that actually makes sense.

Thank you all in advance.

Shelly_D
 

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I just got back a MA6200 I loaned to a customer. I will pull the bottom cover and take a picture next week when I reopen the shop.
 
MA6200 Challenge

Hello shelly_d

Here is a picture from the MA6200 front without front panel

you can see this way where the board is fixed on chassis and how the foam is positionned

c_dk will send you picture from inside
 

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clinic-audio said:
Hello shelly_d

Here is a picture from the MA6200 front without front panel

you can see this way where the board is fixed on chassis and how the foam is positionned

c_dk will send you picture from inside
Click to expand...

OK:

What foam? Don't mean to be flippant but I have never seen foam inside an amp before. My example has non and had no evidence of any. What was it there for and how thick was it?

Thanks for the image it is helpful with the DIY mods for the new board and mounting I need to make.

Thanks

Shelly_D
 
The foam is there to make sure the light from the indicator lamps, does not "leak" to the adjacent indicators.

Is the glass there.....
 
c_dk said:
The foam is there to make sure the light from the indicator lamps, does not "leak" to the adjacent indicators.

Is the glass there.....
Click to expand...

Yes and intact. I removed it and stored it safely to avoid costly accidents like I am VERY prone to do. I took photos of front and rear but it's too late for me to go through the effort of transferring them from camera to computer so I will post them tomorrow.

It is small thin strips running vertically along the back of the glass face? If so, then no I do not have the foam. I see the spot where they were glued to the face plate but no foam is there.

Shelly_D

It occurs to me that you may be referring to a strip that might run horizontally across the power guard indicator lights, where there is a dark stain in your photo. I will need to look at my photos or faceplate to check that but I suspect that is gone.

Shelly_D
 
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I took the picture yesterday.....misplaced the SD card.

Found the card.....under a MAC4200 schematic.....I wonder why...

Don't know how much it will help.
 

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Yes it does help quite a lot. Tells me what orientation the images in the manual are and how the switches are laid out. This tells me the direction I was headed in was correct.

My guess as to why the switches and the board were removed where that two switches were damaged and several of the remaining ones were (I suspect) victims of America's passionite love affair with sugar water in its various flavors. I think that the owner removed the board and switches in a abortive attemp to repair it. Why he/she did not follow through may be because the board and switches are no longer supported by Mac. I am improvising (along with the very able help of my 19 year old son for switch mounting hardware.

Thanks for the pic.


Shelly_D
 
I forgot to post.....board is 14.5 cm wide, approxiamately 6 cm deep.

Expanding Patrice's schematic post to that size should help your layout.
 
c_dk said:
I forgot to post.....board is 14.5 cm wide, approxiamately 6 cm deep.
Click to expand...

That agrees with my measurement of the switch mounting bracket that I do have, which I measured at 15 cm. (150 mm). My replacement may need to be deeper because of the improvizational nature of my mounting system and the longer length of the switches I am using but from the photo it looks like I do have a cm or two to play with.

Thanks for the help.

Shelly_D
 
Digi key has a great selection of these switches. After Glenn posted a Marantz power switch replacement from them I started stocking them. A solution for a dozen other brands.
 
I actually found a surplus house selling 8 pole double throw pushbotton switches for $1.25 each. have 20 of them comming. I'm going to use them for this and to replace the filter switches in my Dynaco Stereo 400, which actually need 8PDT in that spot.

Thanks for the tip.

(By the way, that surplus house is called Electronics Goldmine. Only my 2nd order with them so I have no track record on how their service really is.)

Shelly_D
 
Need more help

Could use a little more help.

I have the switches now and have a mounting bracket made up (thanks to my son :banana:) and a physical layout for the switches that works, proper spacing for the board and everything. What I am struggling with right now is the grounding scheme and ground planes on the circuit board. From the images it looks like there are at least 2, possibly 3 ground plans, none of which are connected together on the board. I can understand why (prevent ground loop hum I assume). What would help me now is to know if the LED ground, pin 9 from the display board, is physically part of the the ground plane of pins 11, 12, & 14, the Left Channel Ground. I would like to get the grounding at least something like the original.

Thank you All.

Shelly_D
 
Patrice's scan does not resolve the board traces......

The LEd grounds are 9 and 42.....

14 and 15 are the input shields.....12 and 13 are the output....

Have you checked with Mac parts for a schematic?
 
MA6200 Challenge

hello !

Patrice's scan does not resolve the board traces...... yes , this is not my scan but a file I download from the web...

Send me a PM and I will scan you the right page in high definition . This, will help you to "make " another board !

:thmbsp:
 
clinic-audio said:
hello !

Patrice's scan does not resolve the board traces...... yes , this is not my scan but a file I download from the web...

Send me a PM and I will scan you the right page in high definition . This, will help you to "make " another board !

:thmbsp:
Click to expand...

A good scan will help (PM sent). Better even then that would be someone's eyes on the actually board to verify one way or the other. That may be too much to hope for though.

Shelly_D
 
MA6200 Challenge

PM and answer sent !

you did not mention if your MA6200 is serial number before BX5302 or after .It is important for spare part numbers and avoid mistake :thmbsp:
 
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