I like my TR-2, but then I like mashed potatoes, so consider the source. You can check all around Q6, and if you see +5.5VDC or so, then I was wrong. But if you see '0', D1 is open, D4 is shorted, or C9 is shorted. If you can signal trace it, you'll get it. I would do it, too, since it is a fun...