JVC boombox
Running well for many years.
New laser unit should usually solve reading problems. PS ok
Besides cables what else can be at fault. Electronics on main board?
Running well for many years.
New laser unit should usually solve reading problems. PS ok
Besides cables what else can be at fault. Electronics on main board?
You may try to replace c906 with a good 100nF MKP.
Does laser fire-up at TOC reading ?
Regards,
Tibi
Does laser fire-up at TOC reading ?
Regards,
Tibi
Replaced C906 electrolytic cap with 0.1 uf mkp cap. Still display 00. Laser beam good, checked using camera
There are plethora of parts that may generate this behaviour. It is very hard to diagnose without good tools.
I'll try to give some indications:
1. Check optical cable and connectors CN901. These may oxidate and generate such problems.
2. Check power supply voltage and noise. Voltage must be around 8V. What matter most is noise. This must be under 100mV. If there is noise, replace 7808 and/or electrolytic capacitors. Use an oscilloscope.
3. Check voltage after board regulator made with Q902 and IC903, see pin 11. This must be 5V +/-100mV. Noise must be very low, under 5mV. You may increase C952 to 1000uF/16V and replace C916 to a low ESR/ESL like Rubycon ZA/ZL, Oscon, Polymer etc.
4. Laser noise may be affected by C932 = 47uF. Use a low voltage, top quality cap here, with very low leakage. You may increase this to 100uF. Tantal or Organic Polymer.
5. Check if any pcb trace is oxidated or broken. Original JVC PCB is extremely low quality. Use a multimeter to measure thin traces.
6. Original JVC board make use of a ceramic resonator. This is very jittery and will degrade fast. Replace X901 or use an external low jitter clock.
There are other parts that may induce "no TOC" behaviour, but this are main ones. Hope this will help you.
Regards,
Tibi
I'll try to give some indications:
1. Check optical cable and connectors CN901. These may oxidate and generate such problems.
2. Check power supply voltage and noise. Voltage must be around 8V. What matter most is noise. This must be under 100mV. If there is noise, replace 7808 and/or electrolytic capacitors. Use an oscilloscope.
3. Check voltage after board regulator made with Q902 and IC903, see pin 11. This must be 5V +/-100mV. Noise must be very low, under 5mV. You may increase C952 to 1000uF/16V and replace C916 to a low ESR/ESL like Rubycon ZA/ZL, Oscon, Polymer etc.
4. Laser noise may be affected by C932 = 47uF. Use a low voltage, top quality cap here, with very low leakage. You may increase this to 100uF. Tantal or Organic Polymer.
5. Check if any pcb trace is oxidated or broken. Original JVC PCB is extremely low quality. Use a multimeter to measure thin traces.
6. Original JVC board make use of a ceramic resonator. This is very jittery and will degrade fast. Replace X901 or use an external low jitter clock.
There are other parts that may induce "no TOC" behaviour, but this are main ones. Hope this will help you.
Regards,
Tibi
Thanks Tibi
Already have a citizen clock installed and power supply cap upgraded before. All voltages are ok.
Poor quality PCB may be the cause. May not be able to find
the fault or oxidized part.
.
The ST3 is no good?
Does anyone have an updater list och which products that are useable?
Nevermind, It was cheap so I bought it anyway.
If I get it working I might even invest in a remote.
If I get it working I might even invest in a remote.
Of course. Look what I found a few meters from my office. It has been sitting there for some years at least.
Could anyone tell me how to use the Program button on the Display pcb?
Or it is no use for CD transport!!
Thanks,
Mark
Or it is no use for CD transport!!
Thanks,
Mark
Crystal ageing... I had that not fault but somehow irregular behaveiour if i can sad so. I replaced original after some years with better crystal. Or build a new master clock generator and connect to XTIN pin...
Already installed master clock, output checked OK.
Adjusted laser trimmer and it worked for awhile, and after sometime
Toc error came back.
In fact have 2 units have similar behaviour
Have you checked the physical alignment? Try a new mechanism and see if that helps, they are cheap and common. It may have been bumped or something, and has gone out of whack. Also double-check the caps controlling the laser tracking and focus (you'll find descriptions in LA9242M datasheet).
Hello, on the subject of tracking issues or the transport not reading correctly when using serperate powersupplies:
I modded the PCB to have 8 volt for the motors and 5 volt, as the method discribed in this thread (cut 5 volt line to chips). After this my transport did not read discs well. It was very bad.
Then I connected the grounds of my 2 regulators. And voila no more tracking issues.
When I dont connect the new 5 volt line, the transport does not power up. Meaning that the trace was cut succesfully.
Has anyone had the same issue?
Has anyone supplied different chips with 5 volt and did it work without connecting grounds on the regulator that were fed by different transformers??
*My account has been locked for some reason i have 0 persmission to post, reply, or to message anyone. Had to make a new account. Moderators?
I modded the PCB to have 8 volt for the motors and 5 volt, as the method discribed in this thread (cut 5 volt line to chips). After this my transport did not read discs well. It was very bad.
Then I connected the grounds of my 2 regulators. And voila no more tracking issues.
When I dont connect the new 5 volt line, the transport does not power up. Meaning that the trace was cut succesfully.
Has anyone had the same issue?
Has anyone supplied different chips with 5 volt and did it work without connecting grounds on the regulator that were fed by different transformers??
*My account has been locked for some reason i have 0 persmission to post, reply, or to message anyone. Had to make a new account. Moderators?
Hi Rikkert, I believe Tibi Vicol did extensive tests with powering Shiga with up to 5 separate regs - this was possible on the new PCB the he designed with our help. He ended up not recommending using this many regs, although I have no exact memory as to why. Perhaps he will be so kind as to explain this further, or maybe have a search through the thread. There is a ton of great info here, just buried below heaps of posts with no lasting value.