Hi all,
I'm getting strange issues with this unit and would ask for any suggestion about how to fix them.
Problems:
After loading the disc, I can hear the disc spinning and the unit searching for the TOC but seldom it is displayed on first try, and a "00:00 00" is displayed.
If I keep trying to play, some disc TOC are read while it seems impossible to get it with some others.
After getting the TOC on the display, again, sometimes the playback is successful, sometimes it is not and the drawer typically opens (!).
Besides, sometimes I got incosistencies between the tracks playing and the info displayed.
Anyway, once locked, the unit play fine without any skipping.
I thought to replace all the elco capacitors of the servo unit. I have also bought a chinese spare for the pickup (of course sold as original, but not original), but it's still in its box.
Any advice is welcome,
Stefano
I'm getting strange issues with this unit and would ask for any suggestion about how to fix them.
Problems:
After loading the disc, I can hear the disc spinning and the unit searching for the TOC but seldom it is displayed on first try, and a "00:00 00" is displayed.
If I keep trying to play, some disc TOC are read while it seems impossible to get it with some others.
After getting the TOC on the display, again, sometimes the playback is successful, sometimes it is not and the drawer typically opens (!).
Besides, sometimes I got incosistencies between the tracks playing and the info displayed.
Anyway, once locked, the unit play fine without any skipping.
I thought to replace all the elco capacitors of the servo unit. I have also bought a chinese spare for the pickup (of course sold as original, but not original), but it's still in its box.
Any advice is welcome,
Stefano
A little update.
Today I removed the PCB and started swapping the electrolytics (in a previous tweaking step I had already bypassed all of them with orange drops) with what I had available, looking for higher Voltage, Temp and Capacitance.
I still have to remove 5 of them (and bypass), but while working I stared at 4 small blue caps caring for "buffering" power supply to the dac. They are marked on the BOM as "C Capacitor 1.5MF 25V. Now, at 49, I still have to understand the logic behind printed units of measure. In engineering and physics we're taught prefix with M are 10 power 6 and not 10 power -6: 1MF would be a cap as large as a Truck!!! But assuming it is a damned ceramic 1.5mF and after reading Jung&Marsh papers on caps, they must go! Now, would you suggest me to swap for some film cap (a tight fit, I believe) or what about some Panasonic OS-CON??
I'm really curious to listen to the DAC with better caps, since I already was very satisfied by the previuos iteration: let's hope I can re-assemble it again
Stefano
Today I removed the PCB and started swapping the electrolytics (in a previous tweaking step I had already bypassed all of them with orange drops) with what I had available, looking for higher Voltage, Temp and Capacitance.
I still have to remove 5 of them (and bypass), but while working I stared at 4 small blue caps caring for "buffering" power supply to the dac. They are marked on the BOM as "C Capacitor 1.5MF 25V. Now, at 49, I still have to understand the logic behind printed units of measure. In engineering and physics we're taught prefix with M are 10 power 6 and not 10 power -6: 1MF would be a cap as large as a Truck!!! But assuming it is a damned ceramic 1.5mF and after reading Jung&Marsh papers on caps, they must go! Now, would you suggest me to swap for some film cap (a tight fit, I believe) or what about some Panasonic OS-CON??
I'm really curious to listen to the DAC with better caps, since I already was very satisfied by the previuos iteration: let's hope I can re-assemble it again
Stefano
Attachments
Thank you Mooly!
I was hoping that exchanging el-caps serving the pickup might cure the issue (I read the wonders of exchanging the 5 caps in the cdm-1). That's why I'm exchanging all the el-caps. I will share any follow-up after assembling the unit again (job scheduled in the weekend(s)). I'm now waiting for some freshly bought 2200uF/63V Nichicon FW, to replace the nasty 1.5mF/25V ceramics supplying the DAC, and will bypass them with films.
Thanks for any hint,
Stefano
I was hoping that exchanging el-caps serving the pickup might cure the issue (I read the wonders of exchanging the 5 caps in the cdm-1). That's why I'm exchanging all the el-caps. I will share any follow-up after assembling the unit again (job scheduled in the weekend(s)). I'm now waiting for some freshly bought 2200uF/63V Nichicon FW, to replace the nasty 1.5mF/25V ceramics supplying the DAC, and will bypass them with films.
Thanks for any hint,
Stefano
Thank you Kay Pirinha! (Prosit!)
I thought that a degraded laser was more prone to skip, while this thing - once locked - was playing fine, and thought that the inconsistency between displayed track and playing track was not related to the laser.
Anyway I'll let you know. I love this player for sentimental reasons, but after some modifications the sound of the humble MN-35502 (MN-35502) was very good (at least to me ) and I bet that without ceramics around the dac, it will be able to perform even better!
I thought that a degraded laser was more prone to skip, while this thing - once locked - was playing fine, and thought that the inconsistency between displayed track and playing track was not related to the laser.
Anyway I'll let you know. I love this player for sentimental reasons, but after some modifications the sound of the humble MN-35502 (MN-35502) was very good (at least to me
) and I bet that without ceramics around the dac, it will be able to perform even better!
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I'm curious, too, as I've got some similar issues in my Primare V-10 DVD player.
Best regards!
For general service work you don't really need official discs which are expensive because they are guaranteed to meet specifications such as reflectivity, eccentricity, general surface defects etc. The content looks the same as any other disc when viewed on a scope.
Any disc you use should be a good quality commercial pressing NEVER a CDR or RW.
If you try a dozen different discs in a player, all should meet the spec for reflectivity which is confirmed by all giving similar amplitude of the RF signal. If one disc does give different levels then that is the odd one out (whether lower or higher than the average) and that disc should be discarded for test purposes.
The images here show typical signals and these would be the same whether using an expensive test disc or a typical music disc.
Sony CDP790 and KSS240 Restoration Project
Any disc you use should be a good quality commercial pressing NEVER a CDR or RW.
If you try a dozen different discs in a player, all should meet the spec for reflectivity which is confirmed by all giving similar amplitude of the RF signal. If one disc does give different levels then that is the odd one out (whether lower or higher than the average) and that disc should be discarded for test purposes.
The images here show typical signals and these would be the same whether using an expensive test disc or a typical music disc.
Sony CDP790 and KSS240 Restoration Project
I used to have some Sony lens fluid but that is long gone
Honestly... here is what I use... you want about 70% pure water, 30% Isopropyl and one single small drop of detergent per 10ml. Its not critical but don't overdo the detergent. One small drop in the water.
The lens should look bright and sparkly when viewed with a bright torch. Make sure the cotton bud (use good ones) is only lightly damp, not wet.
What is on the disc music wise doesn't matter. They all look the same on the scope. Just pick reputable big name labels and the vast majority of those will meet the specs easily.
Honestly... here is what I use... you want about 70% pure water, 30% Isopropyl and one single small drop of detergent per 10ml. Its not critical but don't overdo the detergent. One small drop in the water.
The lens should look bright and sparkly when viewed with a bright torch. Make sure the cotton bud (use good ones) is only lightly damp, not wet.
What is on the disc music wise doesn't matter. They all look the same on the scope. Just pick reputable big name labels and the vast majority of those will meet the specs easily.
Your JVC player uses "Optima6S" laser unit. This one, and Optima150, suffers from the same problem. They lose a small amount gain all of a sudden, when being played for some years. Only trick for both of them (except for exchanging them), is to increase the gain a little bit with the potentiometer on the laser unit itself. Try to adjust the pot a couple of millimeters clockwise (if I remember correctly. Could be CCW, it was such a long time ago) and test a CD. If not enough try a couple of mm´s more. I never encountered one, where I had to throw the laser away. They always worked afterwards.
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I always recommend a good traditional analogue scope for general fault finding. They are tough and don't have you guessing whether what you are seeing is some artefact of the scope or not.
A 30 Mhz dual beam type would cover pretty much any fault-finding and design work for audio.
Names to consider include Hameg, Gould, Trio, Hitachi, Tektronix
A 30 Mhz dual beam type would cover pretty much any fault-finding and design work for audio.
Names to consider include Hameg, Gould, Trio, Hitachi, Tektronix
Almost OT but yesterday evening I listened to my CD94 (I bought it 2nd hand some years ago, with some tweak and TDA1541s1) to the very same tracks I had listened last time with the modded humble 574 (both via headphones out, with Beyer DT1990) and the sense of being there was greatly reduced.
I'm not saying cd94 sound was bad, but the 574 was on another level. So, I HAVE to get it fixed BTW, on the board and on the MN35502 datasheet I see 2 mylar caps on (parallel to) the outputs of the DAC and I think that next listening session on the jvc will be without them.
Then I'll consider to improve the 94 or perhaps better the philips304mkII I have lying around, by applying what I've read on the forum.
I'm not saying cd94 sound was bad, but the 574 was on another level. So, I HAVE to get it fixed
BTW, on the board and on the MN35502 datasheet I see 2 mylar caps on (parallel to) the outputs of the DAC and I think that next listening session on the jvc will be without them.Then I'll consider to improve the 94 or perhaps better the philips304mkII I have lying around, by applying what I've read on the forum.
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