Sony MHC-RV22 CD section problem - diyAudio
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Old 19th July 2008, 07:11 AM   #1
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Default Sony MHC-RV22 CD section problem

I have a SONY MHC-RV22 mini hifi system with MP3 and VCD play back.It about 3 years old now and there seems to a problem with it that it tends to skip and stutter during play back of MP3 files. i took it to the service center and they said that its CD optical pickup control know as the BD-49 board was faulty. they replaced it but still the problem comes up at times. I have the service manual for it and thanks to these sony guys this set has an inbulit error logging system. The optical pickup showed the errors of continuous defocussing while reading TOC and tracking not ON. I repalced the lens assembly with a new one (it uses the KSS-213D, and i was able to find a made in jaoan component). the focus error had decreased (comes up once in a while) but the tracking error still comes up. how do i set the tracking on and set the focus correct. also how to set the laser diode current from the preset on the lens, where do i measure it. i'll try to check up the eye patterns on a scope ( i have an old 15Mhz Phillips dual scope).
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Old 19th July 2008, 11:09 AM   #2
Mooly is offline Mooly  United Kingdom
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Hi,
The laser power is factory adjusted --- do not alter pot. Does it still skip on discs ? You really need a manual to adjust. Some models have more adjustments than others. Tracking gain and focus gain can be very non critical. For focus gain if you turn the up the pot (while playing CD) you should hear "white noise" coming from the pickup itself. Back the pot off until noise (hiss) just disappears. For tracking gain you need to identify and 'scope the tracking error waveform. Adjust the pot until the low frequency "fundamental" in the waveform is just at the point of appearing, then back off fractionally. Is there an E-F balance pot ? -- manual required for that really unless you tweak it gently having first marked it's position. This is a super critical adjustment.
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Old 20th July 2008, 01:04 PM   #3
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Thanks Mooly for the help ans suggestions, i have a service manual for the system and have an oscilloscope also, will try to check it out as you suggested.
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Old 21st July 2008, 06:11 AM   #4
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I just replaced the optical lens with a OEM part and found some dry solder joints on the connecting boards. resoldered the joints and the system worked fine. i even used a CDRW MP3 disc an it was working great. i just made a new CD-R of MP3s. the system read the TOC and displays the albums (folders) but cannot play any file. the play command executes and the system returns to the root. checked the error log which displayed an error of statup time limit exceeded. I burned the new discs at 24x in a DVD burner using a philips media. could there be some problem with the media or writing process. i have other CD-R MP3s burned in the same DVD burner at 48x using the same and other media, they play fine. my computer reads the media without any problem. may be i think there are some compatibility issues in burning CDs in DVD burned (especially at slow speeds). i'll check at 48x writing speed. if you all have any other reasons in mind please suggest them.
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Old 21st July 2008, 06:27 AM   #5
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Hi,
Pleased to hear you got it working. There could be compatability problems -- it's hard to say.
I don't myself use MP3 files on CD but do burn quite a few CDR's on the PC. As an experiment a while ago I tried burning at different speeds from slowest to fastest and then played the discs back on an old Philips CD player while looking at the recovered RF (Eye pattern). The faster the burn (in my case) the cleaner and better defined the signal was.
Sorry can't be more help now. Go through the manual and see if any specific adjustments relate to playing discs with compressed files. Any adjustments could become far more critical.
Let us know how you get on.
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Old 22nd July 2008, 11:25 AM   #6
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Play it upside down and see what happens.
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Old 22nd July 2008, 02:07 PM   #7
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I was able to rectify the problem of the system playing different discs by changing the optical pickup with a new sony KSS-213D i seemed to have lying around. I adjusted the laser power as per the label by measuring the voltage drop across an emitter resistor for the laser drive transistor. It plays all discs (CD and MP3s) both burned fast or slow. there still a problem when the player stutters, i checked the error log and it listed the errors as continuous defocussing while reading TOC and tracking not turned on. This system does not have any potentiometers for setting the tracking gain or focus gain, it just does not have any potentiometers for any settings. The system has a separate board mounted below the optical assembly that control the laser assembly and the sled.spindle motors. I'll check if i can replace the RF/focus IC on the board (its an 30 pin SMD CXA 2581NN-T4) if i can find it else i'll need to replace the complete board which will be a bit costly affair.

There is not much of a problem with writing CDs at different in a CD or a DVD burner. However my personal experience is that a CD burner is more reliable for writing CDs than a DVD burner. May be it may be due to the smaller burning spot size of the DVD burner and the slow spin speed of the CD compared to a DVD. I've seen that a number of times that a DVD player stops reading DVDs but reads CDs, just clean the spindle motor brush contacts (removing any carbon deposits) and the player reads DVDs without any problem. PC DVD drives donot have this problem as they use a 3 phase spindle motor with no brush contacts ( a type of brushless motor in which the magnet rotates and the coils are fixed. uses hall sensors for the 3 phase signal generation)
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Old 22nd July 2008, 05:09 PM   #8
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I can't really advise any more on this-- other than too say it won't be the IC (99% sure on that). Are you sure it's OK mechanically, no sticking sled or int sled motor, a bit of dirt between the teeth on any gears etc. I doubt the problem is "electronic" in the sense of a failed component.
Let us know how you get on.

Edit-- I dont know how accurate the inbuilt fault codes are. Try clearing them and then disconnect the sled drive with it playing and see what it flags up.
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Old 23rd July 2008, 04:40 PM   #9
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Thanks for the suggestions Mooly, evn i'm a more of an practical worker more inclined to the analog part of electronics, i believe in tinkering with things a bit and working the old fashioned way than rely on just some newer digital diagnostics (really fail when u r trouble shooting your PC) I'll check up the sled mechanism and motors along with the gears, as soon as i get some time (just busy with my submission of my Ph.D. thesis in electronics, by the way my topic was much related to physics and electronics, i worked on conducting polymer photo voltaics). i was planning to change the complete pickup assembly along with the mechanism but, the complete sony KSS-213D mechanusm is just not available now, it was earlier but only laser unit available now. will get back to u as soon as i test out your suggestions.
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