Arcam Alpha 8 CD problem - diyAudio
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Old 9th January 2015, 11:21 PM   #1
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Default Arcam Alpha 8 CD problem

New member and first post is looking for help, sorry

I decided to try and use my Alpha 8 CD player yesterday, after quite some time. Last time I tried to use it, it seemed to take some time to recognise discs and the it would frequently skip portions of various CD's, so I left it alone.

Today I decided to investigate so removed the top cover to observe what happens when a disc is inserted. It goes through the following process

Drawer closes
Transport moves up
Laser moves to centre of disc
There is a repeated whirring / slowdown sound which changes with the speed of the disc. The disc does not get up to full speed
I have not been able to observe the ( red ? ) laser

I have played about with x-box transports and tweaked laser output in the past, have access to a multimeter, have done component level soldering including IC (but not GBA), have no scope and a basic / rudimentary understanding of how the electronics work.

It seems to me that the laser mechanism may need replacing, but rather than go out and just buy one, it would be great if you could confirm my diagnosis, offer suggestions for other checks to perform and warn me of any installation / alignment issues I may have to face.

The player is fully dismantled and I did find one small piece of white plastic loose upon dissassembly. I have not yet identified exactly where it has come from but there are a number of similar pieces elsewhere on the transport. In the picture below it is placed on the black part of the transport Is this important or not ?



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Old 10th January 2015, 11:55 AM   #2
Mooly is offline Mooly  United Kingdom
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Have you cleaned the lens thoroughly ?

It could well be the pickup at fault but I also seem to recall many Arcam products suffer from dried out electrolytics in the power supply. Might be worth checking.
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Old 10th January 2015, 11:06 PM   #3
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Thanks for the thoughts. I'm pretty sure the lens is clean as I have a large bottle of IPA but I will recheck that.

This one has already had some of the caps replaced as I had a hum/buzzing sound about 5 years ago. The caps that had failed were located under the DAC if I recall quickly.

Is it possible to test the voltage that feeds the laser ?
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Old 11th January 2015, 08:30 AM   #4
Mooly is offline Mooly  United Kingdom
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The laser will be fed from the 5 volt supply and a scope is always the best check because it shows noise and ripple as well as the voltage. A meter may well show a correct 5 volts even in the presence of ripple.

Measuring the voltage to the laser wont reveal much (unless there is a gross problem) because the laser is current fed and incredibly tightly controlled with an optical feedback loop within the pickup itself.

You need to confirm all the rails in the player are good. A meter will show obvious issues but if non are found then without a scope check it still doesn't mean they are actually OK.

The fact its had cap issues would be a good reason to suspect there could be similar issues now or a missed cap from earlier.
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Old 11th January 2015, 08:25 PM   #5
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I would leave it powered on overnight and see what happens in the morning. You mention that you haven't used it for some time and current flow may help restore some faulty contact, cold solder joint or condition a faulty capacitor. If you get it up and running, that means the laser pickup and transport are OK but the player requires some overhauling.
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Old 11th January 2015, 10:01 PM   #6
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I have been able to spend a little time on the player today.

After spending a little time studying the service manual to locate test points I decided to reassemble the player and see if it worked after cleaning the lens.

It did, well sort of
  • The first CD played fine (and sounded great)
  • The second CD played fine, then it skipped on track 6. I cleaned the CD and it played without issue
  • I then put a new CD is (Xmas present). It struggled to recognise the CD, did the laser focussing many times and when it did eventually play it skipped tracks.
  • I put the CD into a DVD player and it played fine, so it doesn't appear to be a faulty CD
  • After a couple of hours I removed the CD from the DVD player and put it in the Arcam which recognised and played it fine.
I looked at the laser when closing the tray with no disc inserted. The red laser was there but looked very feeble to me, more like a glow than a "dangerous" laser.

Although the CD hasn't been played for sometime I wouldn't say that the electronics were generally cool because it resides just above my amp, which might be a problem (and am now going to get some sorbothane feet to act as spacers to increase airflow). Nonetheless it is always possible that the process of re-connecting the cables may also have restored an oxidised contact.

Should my next steps be to complete the work on ascertaining / checking the test points for the different supplies with my multimeter, or does the additional information above point in a different direction ?

Many thanks for all the help so far.
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Old 12th January 2015, 07:57 AM   #7
Mooly is offline Mooly  United Kingdom
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The laser light is near infra red which is why it looks feeble... it is our eyes that can't see it properly.

Most likely issues are caps... I can't specifically say which they would be, just that Arcam products have a certain reputation... and perhaps poor joints but they would typically be around regulators and other "non standard" parts.

You really do need to use an oscilloscope on this... that is the correct diagnostic tool. We are just making educated guesses at the moment.
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