That's great news that it's not a larger issue with the unit in general, but is limited to this board. It narrows things down for troubleshooting. Here's what I'd do if I were in your shoes:
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First, make a visual inspection of the trace side using a magnifying glass. Compare the known good board with the bad board. What you're looking for is anything different...solder bridges (purposely and not), etc. I mention this because of the Sansui receiver I worked on. I'm so used to being careful to NOT make a solder bridge, that one which was required was missing, causing the channel not to function properly. If you see a difference, check it vs the SM and/or take a detailed photo of both and ask questions.
Make a two page component list, one for the working board, one for the inop one.
With the unit unplugged, start with the resistors and measure them on both boards. You can do this without pulling any. Again, you're looking for differences in readings between the L and R channels of the inop board, but you also have a functional board to compare things to. Even if the value seems off what the scat calls for, if it is consistently off between boards, the resistor is likely fine and you're just seeing circuit interactions. You can always pull a leg later if in doubt to measure it w/o interference from other components.
If nothing turns up, you may need to start pulling components on the inop board to check them out of circuit...caps, transistors, and diodes if there are any.
In addition to the visual inspection, you can use the continuity function of the multi-meter to check for broken traces that don't show up with the visual inspection.
With a litle bit of time, we'll get your board functioning again so it can go into the other unit or back in this one. For now though, don't do any recapping of the good board. Listen and enjoy the fruits of your labors so far.
Oh, and to answer your question, no. Leave the bad board out for now and see if we can find the issue without power applied. There HAS TO BE some component, wiring, trace that's bad ON THE BOARD and that should show up with basic testing. Just take good notes and something WILL pop up as a bit off. And potentially, it could still be switch related since your new board has different switches attached to it.
EDITED SOME TEXT.
First, make a visual inspection of the trace side using a magnifying glass. Compare the known good board with the bad board. What you're looking for is anything different...solder bridges (purposely and not), etc. I mention this because of the Sansui receiver I worked on. I'm so used to being careful to NOT make a solder bridge, that one which was required was missing, causing the channel not to function properly. If you see a difference, check it vs the SM and/or take a detailed photo of both and ask questions.
Make a two page component list, one for the working board, one for the inop one.
With the unit unplugged, start with the resistors and measure them on both boards. You can do this without pulling any. Again, you're looking for differences in readings between the L and R channels of the inop board, but you also have a functional board to compare things to. Even if the value seems off what the scat calls for, if it is consistently off between boards, the resistor is likely fine and you're just seeing circuit interactions. You can always pull a leg later if in doubt to measure it w/o interference from other components.
If nothing turns up, you may need to start pulling components on the inop board to check them out of circuit...caps, transistors, and diodes if there are any.
In addition to the visual inspection, you can use the continuity function of the multi-meter to check for broken traces that don't show up with the visual inspection.
With a litle bit of time, we'll get your board functioning again so it can go into the other unit or back in this one. For now though, don't do any recapping of the good board. Listen and enjoy the fruits of your labors so far.
Oh, and to answer your question, no. Leave the bad board out for now and see if we can find the issue without power applied. There HAS TO BE some component, wiring, trace that's bad ON THE BOARD and that should show up with basic testing. Just take good notes and something WILL pop up as a bit off. And potentially, it could still be switch related since your new board has different switches attached to it.
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