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Old 21st October 2010, 11:25 AM   #1
liquias is offline liquias  Israel
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Join Date: Jul 2004
Location: israel haifa
Default CD Alignments

Hi guys,
This revolves around two issues.
Recently I have done some extensive repair work in my CD player (Sherwood CD1000C).
CD player now works, it plays CDs and everything, but I am quite sure it is not aligned properly.

First issue is mechanical:
During mechanical repair, I had to lift the plate from the spindle motor, and I am not sure if I replaced it to the correct hight.
How do I know what the correct hight is, and what is the best way to adjust the hight to that level ? also what are the tolerances for "correct hight" ?

Second issue is electronic:
I have recently replaced the pickup, and followed the instructions in the service manual as best as I could, to align the new pickup unit to the player.
I cannot run all procedures, as described in the SM, since some of them involve some equipment I do not have. I have a 'scope and oscillator, and of course, a DMM. But I don't have a jitter level meter nor an "auto level meter" (what is that ?) to follow every alignment instruction in the service manual.

I have a strong feeling I am over driving something in the pickup (it sounds funny - some high pitch sound - woooo is audible when stating to play a CD or when the player reads the TOC). and I wouldn't want to shorten the new pickup's life span. pickup is a kss210a and the alignment procedure is attached.

I have some experience with replacing pickups and usually if I get into the alignments I only adjust the RF "eye pattern" to look as best as possible. This one is different though.

Any suggestions ?
Attached Files
File Type: pdf cd1000c alignment.pdf (161.5 KB, 81 views)
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Old 21st October 2010, 04:08 PM   #2
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Join Date: Oct 2006
The noise from the laser is from either the focus or tracking coils, or both. Manuals, especially older ones, always have you over crank the focus & tracking gains. The proper procedure is to, while looking at the 'rf' or 'eye pattern' on the scope, turn down(hiss gets quieter) each one, focus & tracking gains, until you start to see the pattern on the scope go wobbly, then turn each gain back up to a little bit higher than where the pattern goes stable again. You should do this with several different cd's and cd-r's(if it plays them) to be sure you dial in the best gains. At this point, the noise should be low enough to be inaudible from a foot or so away with lid off. Oh, and focus offset is probably also mis-prescribed. Adjust focus offset to get the tallest & clearest rf pattern on the scope(usually corresponds with a dip in focus coil noise level).
As for the platter height, it is not super critical with this sort of transport, but, with the laser at home position with it's dust cover partially under platter rim, there should be about 2mm space between, which would put the disc surface about 4mm from the lens, more or less. If it is having no trouble playing, it's clearly in range.
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Old 23rd October 2010, 01:32 AM   #3
liquias is offline liquias  Israel
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Join Date: Jul 2004
Location: israel haifa
Dear stephensank,
I tried following your advice as best as I could, and I think I got some pretty good results.
I started out by adjusting the focus bias just as you described, and I did find a spot in which there was a noticeable "dip in the noise" just as you described. this was exactly the spot where the eye pattern was the tallest and clearest.

Then I went to adjust the focus gain and the tracking gain. generally I looked for the places where the eye pattern went wobbly and then got back a little.
Again I heard the noise "dipping" a little lower with each "sweet spot".

I have one more adjustment trimmer marked "e.f. balance". I am not sure exactly what this one does, but again I tried to adjust it to the most stable and tallest eye pattern.
What does this one do ? How should I adjust it ?

In any case, the player is now much more silent, both while starting the read cycle (like when reading the TOC) and while reading the track's contents (playing music).

I checked the player with several CDs and everything seems to be in order.

BUT, this is not all !
I have a CD-r which is seriously damaged - It actually corroded at some spots. other player I have still manage to read the TOC from this disc and find the beginning of the songs, but the Sherwood was NEVER able to read this disc.
after all the adjusting everything I could, I popped in the CD-r and the player read it completely, with no problems!

I hope the pickup's life span is now out of danger.

Well, I guess all that's left for me to say, is THANK YOU !
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Old 23rd October 2010, 03:23 AM   #4
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Join Date: Oct 2006
If you have no trouble skipping tracks forward & backward, the ef balance is ok. If it has to hunt before hitting a track either way, then it should be adjusted. To get precise ef balance, you need to find the TE tracking error output signal testpoint & hook the scope to it. With a disc running in Pause mode, set your scope time/div slow enough & your vertical gain so that you can clearly observe the + & - going spike in the signal, which is the servo telling the laser to stay on the same 'groove' at each disc rotation. Adjust the ef balance so that the spike is equal height above & below the center line. You now have precise ef balance.
And, yes, it does sound like you hit the other adjustments right on the money. Torture discs like that beat up cd-r can be very good tools for testing.
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Old 26th October 2010, 10:17 PM   #5
liquias is offline liquias  Israel
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Join Date: Jul 2004
Location: israel haifa
Dear stephensank,
I am sorry for the delayed reaction, I've had very little time these last couple of days.
I don't think searching is problematic. Pickup is searching continuously, with no clicking or mechanical interruption. It might be a little slow, I still need to check this out, I'll probably get to it tomorrow.
I was wondering, if the eye pattern can help with the e.f. balance adjustment too?
Second thing I wanted to ask was, if e.f. balance is not set correctly, can this shorten the life span of the pickup ?

Again, Thank you, for everything.
yours,
liquias
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Old 27th October 2010, 02:19 AM   #6
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Join Date: Oct 2006
If the ef balance is way off, the eye pattern will get kind of wobbly, but that you can't adjust finely enough to get accurate setting. The TE test point should not be hard to find. On older players, it was often marked "TEO"(tracking error output), if there was also a TEI(input) point, but would as often be marked just TE or, rarely, TER. If you also have a tracking offset trimpot, which rarely needs tweaking, proper method is to simply check TE/TEO point with dc voltmeter in STOP mode, and adjust for 0VDC.

Neither ef or tracking offset adjusts will have any effect on laser life whatsoever. Only thing that affects laser life, really, is the laser power adjustment. All of the other adjustments are about disc reading ability.
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