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Marantz 140 power amp rebuild

Steven Tate said:
That looks like your bridge rectifier that converts the transformer AC to DC before the filter caps. I do think you have a big grounding problem with those big caps.
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Im thinking the same thing would i have to build a new bracket so that the entire thing is a ground bracket like the original or would adding another thicker gauge wire ground from where the missing factory bracket was and solder it to current metal plate that is sitting between the two negative lugs on the caps do the same thing?
 
Hi mazinkaiser,

Your connections to the two capacitors looks OK, although I cannot see which terminal is negative and positive, I have attached a photo of mine, basically the wiring is the following:

Negative terminal - All white wires, except the larger white wire from the transformer
Positive terminal - All the red wires
The Bridge - positive to negative terminals - All the black wires and the larger transformer wire

Note: The original wiring of the amps has two earth wires from the bridge to each of the amp boards (can be seen in the photo). I connected two additional earths from the bridge to the chassis.

Hope that helps,

Tony
IMG_8507S.JPG
 
Also just to make sure we are on the same page here when i say distortion i mean the speakers crackle as the issue (have heard both terms used to describe this issue on other threads not sure if they are one or the same) and its mainly on parts of the song that have high notes where the vu meter goes high just want to make sure im representing the problem correctly
 
I just switched preamps and speakers to make sure im not just going crazy and i had to crank my preamp to almost 80 to get about as much as half the dial volumw of my sansui 15 watt this time with 98db speakers there really seems to be a power issue going on here i cant believe my 15 watt amp is out driving this 75 watt marantz and that it starts crackling this quick
 
The two resistors connected to the rectifier are to bleed the charge from the big filters when the amp is turned off.

I am at a loss as to what might be wrong, whatever it is it's affecting both channels which leads one to think it might be a power issue as that is one of the few things both channels have in common.
The idea to connect a ground wire from the filters to the chassis was a good one, I had hopes that would be the fix.

Tom
 
Just to confirm, there should be about 12 black wires attached to the bus bar.

Heres one I just did a few weeks back
20190317_092143.jpg

20190317_092158.jpg
 
catrafter said:
The Positive post of the filter that has the White wires on the Negative post should connect to the 'bar' with the many black wires attached to it.
The Negative post of the filter that has the RED wires on the Positive post should connect to the 'bar' with the many black wires attached to it.

A really good photo of the tops of the filter capacitors would help.
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Hey Tom, I know this is an old post, but I'm thinking of getting back into working on units again and would like to start with one of the 140's I have. Looking at your picture I am guessing you drilled new holes for your clamps on the filter caps, can you remember what size clamps you used and what value the filter caps were also, the brown caps on your unit, are they bypass caps and if so, what caps should I use (looks like they go between the ground and the positive of one filter and the negative of the other) Thanks, Rich
 
Hi Rich,
I hope you are well!
Yes, I drill holes so I can mount the caps.
383LX153M063A062
Manufacturer Cornell Dubilier Electronics (CDE)
Manufacturer Part Number 383LX153M063A062
Description CAP ALUM 15000UF 20% 63V SNAP
They fit 35MM clamps.

The bypass caps are 2.2uF 100VDC Panasonic ECQ-E1225KF

Tom
 
catrafter said:
The bypass caps are 2.2uF 100VDC Panasonic ECQ-E1225KF

Tom
Click to expand...

Thank you so much Tom! Yes, I am doing well, it was tough for a while but I'm starting to live life again and cleared off my table to work on some of the stuff I never got to. I fixed this 140 when I first got it, it had some shorted diodes, but haven't hooked it up in several years. Is there anything else that is suspect in these that I should address?

Thanks again, Rich
 
According to the data sheet the positive and negative are across from each other and the other 2 are dummy terminals, traditionally used for extra support. But if you’re not using them you can either fold them over or clip them off.

5779F446-2700-4509-AE04-CF669A6910F0.jpeg
 
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