Mac 1900 Filter Cap Polarity

Nac458

Member
Hello,

I'm in need of some expert help identifying the orientation of the main 9300uf 50V filter capacitors on the mac 1900.

Underneath, there appears to be two black washers/insulators on opposite ends (closest to the transformer and the other end of the receiver) and a main plate that bolts to the chassis that bridges the caps.

How, in relation to the mounting bracket - is the correct way to screw in the new capacitors?

I've attached a diagram from a service manual I pulled (I'm aware there are many versions of the 1900, so I am being weary).

Thanks for your help.
 

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Negative (-) go to ground.

That is what I thought originally. Yet when I powered it with my dim bulb tester - the bulb lit up and I heard a small pop.

Judging by the schematic one positive lead appears to go to ground - would that be correct?

I've attached a real time photo.
 

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That is correct. Did you mark or take the picture before replacing it?
Remember these capacitors are in series.
Nope, I'm kicking myself for not having taken pictures.

I was so excited to replace the old ones - before I knew it, they were out and new ones were going in...

I understand they are in series. In the meantime, I will just have to find the rectifier and follow it back to those resistors.
 
Be patience. Someone on this forum that own the unit will spell out the actual location of the plus and minus for each cap. If you can trace out the resistor R515 then it should clear up.
 
Reasonably sure I have picks from a restore I did a little over a year ago.
Send me a PM rememinder and I'll look for you when I'm home .
 
The green wires coming off the fuses and cap connection block are the negative supply.....therefore the - polarity of one cap goes there, the other cap's + polarity will go to the other red fuse/wire connection block.
 
Does my description of the connecting points make sense?

Actually just found maybe the 6th main filter cap failure in a McIntosh I have seen over the last 40 years........in a MA6200 and yes I did take a picture of it under test.
 
Does my description of the connecting points make sense?

Actually just found maybe the 6th main filter cap failure in a McIntosh I have seen over the last 40 years........in a MA6200 and yes I did take a picture of it under test.

It does, thanks!

I'm just wanting to finalize which terminal goes where on each side.

I took a closer look at both service manuals available on hi-fi engine, and this is my best guess... So farCapture+_2018-06-07-11-32-43.png
 
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