Help Required : Revox B126 CD Player - diyAudio
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Old 25th October 2010, 11:12 AM   #1
dtm1962 is offline dtm1962  Canada
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Default Help Required : Revox B126 CD Player

I am trying to put the final touches on a repair of my Revox B126 CD Player.

The symptoms:

1) The player will play about 40% of my discs perfectly... no skips etc. It will play these discs over and over with no problem....

2) With about 55% of the discs it will spin the disc somewhat faster than normal for 3 seconds and then just stop... not recognizing the disc.

3) With 5% of the discs it will spin the disc fast and then slow and then fast and then slow with a frequency of switching of about 1 second. Once in a while it will play these discs but mostly it will go thru this fast/slow activitiy for more than a minute without stopping or until I stop via LOAD button.

All of the active devices (Opamps/servo control chips/transistors) for the drive except for the LM324 Opamp & Hall Effect sensors on the CD Disc drive have been changed out. 2 Laser assemblies have been tried with the same results. The 4.7Kohm & 22Kohm pots have been changed out as well.

All the electro caps have been changed out including the notorious 33uF have been replaced.

Any idea what this points to as a problem????

I am at the end of my rope for this one as I am going to sell this unit for parts but I really don't want to do this as it is such a beautiful machine.

Please suggest anything I can try!

Thanks in advance
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Old 26th October 2010, 03:53 AM   #2
amc184 is offline amc184  New Zealand
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Still not going, eh? Bummer. You've kind of exhausted the troubleshooting tips I can easily explain, by this stage I would be probing around in it with an oscilloscope following my nose. There is one more thing you can try though; I have a few servo boards around compatible with your player. I can lend you a working servo board which would at least isolate where the fault is. PM me if you're keen.
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Old 26th October 2010, 06:06 AM   #3
nac134 is offline nac134  Canada
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Sounds to me like a transport problem. Are there any tiny little trim pots on the laser head? Also, if you load a disc and then stand the player up vertically, does the problem go away (this can tell help you identify a motor or bearing problem)?
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Old 26th October 2010, 11:44 AM   #4
dtm1962 is offline dtm1962  Canada
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Default Difficulty Reading the TOC MAY be the Fault - READ ON

I was just thinking now..... That I am sure I remember the laser reading the TOC (# of Tracks & Total Time) when I loaded the disc before the failure!. Now I don't get TOC but I get -XX.XX left on disc & Track # ONLY AFTER I press PLAY and change the display options!

Does anyone have a B226 or B126.....that they can tell me if there is TOC (# of Tracks & Total Time) when you LOAD the disc.

Please let me know as this may be a symptom of ?
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Old 27th October 2010, 04:47 AM   #5
dtm1962 is offline dtm1962  Canada
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Default CLosure...

I believe that the TOC issue is non-existent as I reviewed the owners manual and it works the way it actually does.

I made a few fine adjustments today and I got the player to read 95% of the discs I tried including CDR's. For some reason it won't play a couple new commercials discs from the same artist/CD manufacturer, but will play some scratched up CDR's ? weird!

So I am closing this off as I believe the laser is weak and it will probably need a new laser to ultimately play as new.

Thanks for all your help.
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Old 27th October 2010, 04:57 AM   #6
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Hello. I have experienced the exact same problem with a Technics CD player. The problem was with the optical pick-up system, either from dust and dirt that covered the optics or from the aging of the laser diode. I increased the current trough the laser ( by a tiny amount ) and that made the problem go away. I wont go into further detail.
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Old 27th October 2010, 07:29 AM   #7
poynton is offline poynton  United Kingdom
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Quote:
Originally Posted by dtm1962 View Post
................ For some reason it won't play a couple new commercials discs from the same artist/CD manufacturer, but will play some scratched up CDR's ? weird!

....................
I once had a CD player with incredible taste (Akai, I think) !!

It would only play the 2 Eric Clapton CDs I had and no other at all.


No matter what I tried, it stayed the same.
So I put it on the junk pile at my shop and sold it to a Japanese student.
Maybe he knew something I did not ?


Andy


.
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Old 27th October 2010, 07:43 AM   #8
amc184 is offline amc184  New Zealand
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Maybe he just really liked Eric Clapton.

Seriously though, I have had the same symptom where the player doesn't show the number of tracks (though on my players it would just display 99). It was due to the laser mechanism being on its last legs. If you want to test for that problem, measure the laser current consumption. To do this, check the voltage drop over resistor 3101. If it's higher than about 800mV, the laser mechanism is stuffed.
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Old 27th October 2010, 11:40 AM   #9
dtm1962 is offline dtm1962  Canada
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Hi ANton:

I believe you are correct... that it is very sensitive with the weak laser etc.

I basically sold it for $125 (cheap) with the understanding that the laser is weak and ultimately needs a new laser. I believe I have over $300 into it now with the cost of the unit + parts so I have to move on......

Thanks,
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