Cambridge Audio 640C V2, lightning strike! - diyAudio
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Old 24th May 2013, 04:49 PM   #1
sangram is online now sangram  India
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Default Cambridge Audio 640C V2, lightning strike!

Hi

My friend had the player hooked up to the wall and on standby when a big electrical storm hit.

The player showed no signs of life and after some measuring we figured the main toroid had copped it, no winding resistance from the common terminal to either the 110 or the 230V windings.

CA sent over a (pricey!) new transformer and we fired it up and it seemed to work OK. We were having a bit of an issue with the front panel buttons but we put that down to the age of the player and the humidity (always >75%) causing the switches to go bust.

Anywho, we shut the lid, hooked it up to an amp and got no sound from either channel. The digital output was then tested and found working, but the analog wouldn't play anything.

I started poking around a bit on the board, removing the I2S connection to see if that changed anything, probed around with a analog signal probe, and the right channel came to life. Left channel still dead as a dodo, and shows 1.25-1.35VDC on its outputs (as opposed to 2.5V as is expected, and measured on the right channel). The Vregs for Vd and Va are steady at 5V, but run very, very hot - much hotter than the working channel. And the area above the chip is also quite toasty but nothing burning and nothing stinking.

Click the image to open in full size.

We've ordered a replacement DAC (which is as of now the prime suspect) and will be getting some more 1N4148s which we snipped off while testing (in case they had blown junctions and were overloading the output), but really was looking at anything else I can test/do before we take the drastic step of replacing the DAC chip. As far as I can tell from the schematics the DAC is being used in hardware mode and has no logic connection to the servo, but I couldn't be sure.

Full manual is available here: http://www.elektroda.pl/rtvforum/download.php?id=514397
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Old 24th May 2013, 07:23 PM   #2
marce is offline marce  United Kingdom
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There is probably more problems hidden away, and other components may be on the point of failure, after such an event.
Usually its skip time.
Just had a look at the manual, it was a BIG shock, these were made down to a budget.
Good Luck.
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Old 24th May 2013, 08:29 PM   #3
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I would view this as an exciting opportunity to build some DIY stuff! Personally, if I were in your friend's position, I would buy an inexpensive sound card for my computer (assuming your friend has a desktop) with S/PDIF or TOSLINK out, then build one of the many cool DACs available. There's a group buy happening right now for a very nice S/PDIF DAC with a power supply and parts kit here: ES9023 / WM8804 S/PDIF "Subbu DAC V3" GB Interest
Your friend can probably drive his receiver/amplifier with the computer's headphone outs until you two are done building it.
That's just what I would do. Oh, wait . . . That's what I did do when my CD player died!
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Old 25th May 2013, 07:46 AM   #4
sangram is online now sangram  India
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@marce: I am of the same opinion as you and have already told him that this will be a shot in the dark, and that the chances of total success are slim. Though the player cost about $550 new, my friend got it for about $300 from the first owner, so it didn't pinch as much. He lost an amplifier to lightning last year, and that has to be gutted and redone from scratch (using modern circuitry). I asked him to get his wiring and switches checked, maybe now he might consider doing that as well.

@Byron: My first suggestion to him was to get a DAC and use the player as a transport, the reaction was pretty negative. This is our last shot and if it doesn't work he will simply put it away till he can afford a DAC. Times aren't good for either of us else I would have considered building a DAC for myself and 'loaning' him my Buffalo. He already has a lovely soundcard - he got a E-mu 0404 for really cheap but it's boxed away.
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Old 29th May 2013, 03:08 PM   #5
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hi , im using a CA640C as a transport so i dont need the analog section of the player , is there an easy way to disconnect the analog stage from the transformer ?
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Old 29th May 2013, 03:28 PM   #6
sangram is online now sangram  India
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I'm not sure there is, actually. The higher voltage winding powers the entire output board (digital + analog) and is regulated down to the required voltages by 3-terminal 78xx regs. The master clock is also one the same board and powered by the same transformer (yuck!).

The rectifiers for the analog and digital are probably separate though, so simply desoldering those will probably work, or even disconnecting the supply regulators for +/-15V?
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