Following on from my request earlier in the week for a schematic set for a NAD cassete deck that was an urgent repair for Christmas, having not come up with any diagrams, I decided today to fling it back up on the bench, and have a go at the fault 'blind'.
The basic problem was no record, no playback, no meter indications in either mode. When playing back a known good test tape, there was input to two pins of the Sony Dolby processor IC, but no signs of anything coming out on any other pins. I couldn't even find the correct data sheet for this device ...
Based on the fact that the chip was surrounded by little pale blue electrolytics, which I have had give trouble on many different items of electronic equipment over the years, I set about measuring the resistance to ground at every pin on the IC. Two pins, exactly opposite one another, and with similar looking print traces, going off in the same direction, both read pretty close to zero, When I followed the traces round the board, they both arrived at 220uF 10v caps, sitting side by side. When these were removed, both read short circuit. How odd is that ? When they were replaced with 16v types, all record / play and metering functions were restored.
Just goes to show, with a bit of perseverence, and a lot of years' experience, just occasionally, you *do* get lucky ... :-)