Cap Coupled Receivers?

i am trying to figure out what the board is in pic 5 . can you take a pic of how its wired to the other boards ?
and do those black boxes have adjusting screws ?
 
there will be a 1000uf capacitor connected to pin 2 of each module . the + side of that capacitor is where you can measure centre voltage . be very careful .one slip there and the module is toast .
rail voltage goes to pin 3 ..and most likely the fuses are for that and you can measure right on the fuses .
 
i am trying to figure out what the board is in pic 5 . can you take a pic of how its wired to the other boards ?
and do those black boxes have adjusting screws ?

No adjusters on the black boxes. They both read "Sanyo LD3120". They have 9 pins each. 5 on 1 side & 4 on the other. I'll send some pics later or tomorrow.
Thanks petehall !!
 
Nothing to touch and nothing to measure. Just to be clear, there's nothing of interest to measure in terms of DC offset at the output, assuming the caps are good. Forget whatever mV you might see there as it's time and load dependent. With no load it could be way higher, but that's normal.
 
all i would do is replace all the electrolytic caps apart from the tuner if its working ok . then call it done if it plays music ok .
 
Thanks for all your help, men. Really ! I'm learning & it's fun. I'll still send bottom pics tomorrow of the whole unit & for the board in pic # 5. I'm curious too.
Cheers !!
 
Here is a very very long thread that explains D.C. Offset in great detail. It is too long to read the whole thing, but read the first 8-10 pages and you will learn a ton. Notice none of it applies to cap coupled amps, but you will notice that occasionally someone measures their 2230 or 1060 and is shocked by their reading. Very educational thread.
Steve

http://audiokarma.org/forums/index.php?threads/amplifier-distortion-dc-offset-and-you.5634/

Will do ! Thank You !!
 
i am trying to figure out what the board is in pic 5 . can you take a pic of how its wired to the other boards ?
and do those black boxes have adjusting screws ?

Here's a couple o' more pics relating to the board in pic 5. I traced the large wires & it looks like pic # 5 is the phono board. So I guess that's out of the way for now ?

PB040248.JPG PB040249.JPG
 
all i would do is replace all the electrolytic caps apart from the tuner if its working ok . then call it done if it plays music ok .

Which caps have priority as 1st being replaced ? I didn't see any leaky or swollen ones. Here's 3 pics. Correct me if I'm wrong, but I think the 2nd & 3rd pics have the most important ones ?
I hope I'm going about this right. I know they're all important.
Thanks !
PB040255.JPG PB030243_1.JPG PB030242.JPG
 
It's wide open and should be easy to work on. I would replace all of the electrolytic caps a board at a time, testing with Dim Bulb Tester after each board. Start with the power supply, test it, replace the filter cap, test it, then move through board by board. The tuner board could likely be left alone, but replacing the electrolytics doesn't seem to mess with alignment. I replace them all.
 
Yeah, & I'm convinced my unit is cap coupled too. Still need to finish reading the thread Steve Tate suggested. Hey, I may be little slow, but I'm learning !
yes it is cap coupled . the 1000uf caps near the modules will be the output caps .
 
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Some questions on the caps, please. These are for the 2 boards & the can one in my last 2 pics:
1) Should I get a little higher voltage rating then what's on 'em as long as I get the correct uFs ?
2) What about temp. rated ones ? (If it applies)
3) Any suggestions on brands ?

Time to make a list. Thanks !
 
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