There's a result then ...
in [Repair]
|
Prev: LPC quad UART garbling 8th bit in TX data - difficult toreproduce - any ideas?
Next: There's a result then ...(NAD/Holiday Wishes)
From: William Sommerwerck on 26 Dec 2009 06:58 > Just goes to show, with a bit of perseverence, and a lot of > years' experience, just occasionally, you *do* get lucky... :-) That is not luck. Given the problem -- no recording and no playback -- I assume you started with something common to both processes, the power supply, and found that the voltages were more or less correct. Where to from there? It's easier to check playback than recording, so you inserted a test tape and found the signal stopped at the Dolby chip. That pointed to either the chip or the surrounding components. The latter are the easiest to check, so... No, Arfa, it was not luck. It was good troubleshooting techniques all the way.
From: Arfa Daily on 27 Dec 2009 19:58 <snip> it still *felt* lucky to have dropped on a > short >> circuit cap (and its mate next door) that was measurable in circuit ! > > You're confusing luck in the problem being due to a readily replaceable > part, and luck in troubleshooting it. "Yes" to the former, "> > Well, whichever way you look at it, that brings us right back around to the start. Sometimes you gets lucky. I got lucky ... :-) Arfa
From: Arfa Daily on 22 Jan 2010 20:18
"Arfa Daily" <arfa.daily(a)ntlworld.com> wrote in message news:KAzYm.104267$II.69134(a)newsfe22.ams2... > 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 > test |