CD4 - Play button does not always work.

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zbyszek
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CD4 - Play button does not always work.

#1 Beitrag von zbyszek » 06.03.2017, 11:00

Hello,

I have an issue with my CD4 player.
On some CDs, when I press the Play button, it does not start playing and behaves as if the Return button was pressed (Display shows the "Disc" text only, and the LED above the Return button is shining).
When I press the Play button again, it starts playing normally.

Has any of you had a similar issue?
PS500, CD4, T2, CSV 13, Regie 501k, Regie 510, L60

juergen
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Re: CD4 - Play button does not always work.

#2 Beitrag von juergen » 29.03.2017, 21:10

Hello zbyszek,

I am not sure I fully understand your problem description. The LED status you describe ("disc" indicator and LED above the "return" button are on) is the default state my CD4 shows when it is idle, with a disc inserted. I do not have to press the "return" button to reach that state.

So are you saying that your CD4 sometimes ignores the "play" button completely, and behaves like no button was pressed at all? If so, are you sure that this occurs for specific disks, while others are not affected? A bad contact in the switch seems the most likely cause, but that should of course be independend of the specific CD that was inserted. What happens if you press the "play" button a bit stronger and longer -- does it react more reliably then?

Best regards,
Juergen

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Re: CD4 - Play button does not always work.

#3 Beitrag von Paparierer » 29.03.2017, 22:53

Hi Zbyszek,
does this happen not in between listening to a cd, but when you put a new fresh disc in the player?
Then it may not be a problem with the <play> button, but with
- the disc sensor,
- the power supply or
- the laser itself.
I'm just guessing but some knowing specialists here should be able to locate the cause of the problem.

Yours, Gereon
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juergen
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Re: CD4 - Play button does not always work.

#4 Beitrag von juergen » 30.03.2017, 22:07

Good points from Gereon, but I think
  • The disk sensor is probably working fine. If it would not detect a disk, the "disk" indicator would not light up.
  • The laser is probaby not to blame either. If a disk has been detected by the disk sensor and you press "start", you should hear the motor spinning up, and should see "track 1" in the display right away. I believe that the player only tries to read the disk after those actions, and hence the laser would only come into play at that later point in time.
The power supply could theoretically be the culprit, but I think the button itself is the more likely cause for this intermittent fault. Try the "press it harder" test. ;-)

zbyszek
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Re: CD4 - Play button does not always work.

#5 Beitrag von zbyszek » 31.03.2017, 20:15

Thank you for your answers.

The issue is not with the Start button not being pressed strong enough.
The player recognises that the Start button was pressed, because it starts spinning the disk.
However, it does not start playing the disk, but stops spinning and behaves as if the disc ended (or the Return button was pressed).
When I press the Start button again, it starts spinning the disk and plays it normally.

The issue is very random in its nature. Sometimes a disc will play normally, and sometimes this issue will occur.
PS500, CD4, T2, CSV 13, Regie 501k, Regie 510, L60

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Re: CD4 - Play button does not always work.

#6 Beitrag von juergen » 31.03.2017, 20:50

Ah, so it does start spinning the disk! That's the part I had not picked up from your initial post.

At that point, the CD4 switches on the laser and actually tries to read the disk (table of contents). Apparently it can't always read the disk properly. Your observation that some specific disks are affected makes sense too, then.

Does the problem also occur for commercially produced (stamped) CDs? If only home-burnt CDs give you problems, your CD4 may well be within specifications -- the old CD players were not designed with writable CDs in mind, and may not handle them robustly.

Have you already cleaned the lens of the pickup? Remove the top lid of the enclosure to get to it, using a hex key. Let's hope that this will do the trick. (If it should be the laser starting to wear out, that one is very hard to obtain and expensive for the CD4.)

EDIT: There are other potential causes too. The hub supporting the CD may have slipped in height, which may bring the laser to the edge of its focusing range. Discussed here for the CD3, but I believe I have seen it described for the CD4 as well: http://www.braun-hifi-forum.de/viewtopi ... =701#p7208" onclick="window.open(this.href);return false;.

Stephan
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Re: CD4 - Play button does not always work.

#7 Beitrag von Stephan » 02.04.2017, 09:48

Good Morning,

The issue is a known issue. I remember there is a bulletin on the Service CD.
I am just relocated and could not find the CD. Probably someone else could have a look please?

Regards

Stephan

zbyszek
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Re: CD4 - Play button does not always work.

#8 Beitrag von zbyszek » 02.04.2017, 11:14

Indeed, there is a bulletin listed on the radiodesign.de page. None of the links is working though.

I will be grateful if someone shares the info on the fix for this issue.
PS500, CD4, T2, CSV 13, Regie 501k, Regie 510, L60

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Re: CD4 - Play button does not always work.

#9 Beitrag von juergen » 02.04.2017, 15:16

Many thanks for making that connection, Stephan!
The service bulletin seems to be spot-on, and the cause is more subtle than expected. Translation of the service bulletin:

Issue: CD4 does not start up upon first "Start" command (after power-on and insertion of a CD); it starts normally only after a second "Start".
Cause: Servo amplifier is detuned.
Fix: Connect oscilloscope to test point "FE" and GND. Adjust servo amplification via VR102 to exactly 0.3V DC, according to service instructions (page 6).

The service manual for the CD4/2 (which is the only one I have) clarifies that one should adjust the average DC offset measured on test point FE; there is some "noise" signal superimposed to that. Contrary to the service bulletin, the service manual recommends 0.2V DC. Maybe it was found later that this value is borderline, and hence the service bulletin recommends the higher value?

Regards,
Juergen

zbyszek
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Re: CD4 - Play button does not always work.

#10 Beitrag von zbyszek » 02.04.2017, 15:59

Thank you for your help. I have fixed the issue. :D

The service manual for CD4 gives the same 0.3V value.
Before adjustment, the value was 0.6V.

Also, the measurement has to be done while a CD is playing. When stopped, the value is higher, around 0.45V
PS500, CD4, T2, CSV 13, Regie 501k, Regie 510, L60

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