Help!!! Need help with Capacitor C322 leg connections on MPX Marantz 150 Tuner

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old_marantz

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I’m a newbie and don’t read circuit boards. I was recapping a capacitor that’s on the rear PCB board of the Marantz 150 MPX board. It was so loose it just fell off. I attached the schematic.

The Capacitor is C322 10uf 16v. One leg wire seems to be attached to R348 (visually) but Im not even sure of that. Very tight area on the board. I have no clue where the other leg connects.

Can someone enlighten me. Mucho Thanko!2026-03-20_16-18-54.jpg
 
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From the Model 150 SM. The (+) lead connects to R346 and R316, and the (-) lead connects to R315.
There should be component reference markings on the component side of the PC board as shown in the photo below.
Screenshot 2026-03-20 201605.jpg
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ok..I am confused for sure..but your post is right on..let me show some more pics

At the top right corner of the picture is one of the legs from the capacitor. The other leg fell off. I’m just not sure where the other leg attaches. This capacitor is on the opposite side of the board where all the other electronic parts are attached. So there isn’t a printed hole on the PCB board for c322. Just would like someone to point out where that other leg attaches.

If you turn over the board, the remaining leg looks like it’s attached to top of R336. I have no idea where the other leg attaches. Maybe this an undocumented cap add of the service manual??

I’ve looked for service updates for the 150 but I haven’t come across any.pic1.jpg
 
If you turn over the board, the remaining leg looks like it’s attached to top of R336. I have no idea where the other leg attaches. Maybe this an undocumented cap add of the service manual??

I’ve looked for service updates for the 150 but I haven’t come across any.
 
old_marantz said:
The Capacitor is C322 10uf 16v. One leg wire seems to be attached to R348 (visually) but Im not even sure of that.
Click to expand...
C322 is not near to where the broken leg is soldered. (see photo comparison). I'm not sure why you think the missing cap on the back is C322?
old_marantz said:
So there isn’t a printed hole on the PCB board for c322. Just would like someone to point out where that other leg attaches.
Click to expand...
Your photo above shows an electrolytic capacitor soldered into the board at location for C322.
old_marantz said:
If you turn over the board, the remaining leg looks like it’s attached to top of R336.
Click to expand...
The broken capacitor leg that is soldered is connected to R336 and H305(C) (shown in dotted blue line). Now we need to figure out where the other lead was soldered to.
Do you have a photo of the cap that came off of the broken lead so we can determine the value? Maybe that will help.

Screenshot 2026-03-21 215209.jpg
 
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So I found a photo of the 150 P300 board backside on the internet and compared it to your blurry photo and tried to match up pads.
The photo that I found has a cap soldered to the backside so I tried to see which pads it was soldered to.
Here is a comparison of yours (L) and internet (R), with colored circles matching solder pads.
It looks like the cap is soldered to transistor H305 emitter and collector, circled in pink.
Looking at the schematic, that the (-) negative side of the electrolytic should be soldered to the pad that connects to the emitter and ground, which I think is your broken lead.
The cap positive lead should connect to the H305 collector.
Can you tell what the original cap what lead was broken off, + or -?

Screenshot 2026-03-21 230648.jpg

Screenshot 2026-03-21 231119.jpg
 
dankik said:
So I found a photo of the 150 P300 board backside on the internet and compared it to your blurry photo and tried to match up pads.
The photo that I found has a cap soldered to the backside so I tried to see which pads it was soldered to.
Here is a comparison of yours (L) and internet (R), with colored circles matching solder pads.
It looks like the cap is soldered to transistor H305 emitter and collector, circled in pink.
Looking at the schematic, that the (-) negative side of the electrolytic should be soldered to the pad that connects to the emitter and ground, which I think is your broken lead.
The cap positive lead should connect to the H305 collector.
Can you tell what the original cap what lead was broken off, + or -?

View attachment 3725768

View attachment 3725769
Click to expand...
Wow…you’re a great detective. So you’re saying the + leg attaches to H305? If you look at the solder of H305 there is a brownish pit …maybe that was where the leg was.

I assume I should precede?

I appreciate all the responses! Nice work every one!
 
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Looking at your photo of the two caps above, it looks like the bad one still has the (-) lead attached which means that the lead that is left on the board is the (+) lead.
So, I would guess that the new cap (+) should be soldered to the H305 collector and the (-) soldered to H305 emitter as shown below.

Screenshot 2026-03-22 085135.jpgScreenshot 2026-03-22 085822.jpg
 
I really appreciate the help. I’m just an occasional solder and pretty dumb. I really appreciate you guys that know this stuff forward and backwards!
 
The plot thickens.
So I unsoldered the leg that remained and it was from the R336. It was on the leg of the side of R336 resistor with red circle. So, not sure what to do.
So why would a capacitor need to be in the resister path? I believe jap FM is different than USA FM.
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