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From: Tim Schwartz on 24 Dec 2009 08:45
On 12/23/2009 8:36 PM, Arfa Daily wrote:
> 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 ... :-)
>
> Arfa
>
>
Arfa,

Glad you found it, and sorry I missed your original post, as I've
likely got that manual packed away somewhere.

I would also like to echo Mark's wishes to all for w great holiday
season and New Year.

Tim Schwartz
Bristol Electronics
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