Troubleshooting CD Players
- Thread starter dr*audio
- Start date
Rotel RCD-945AX Backlight
Just picked up a mint condition Rotel RCD-945AX for 20 dollars. Sounds real nice, but the backlight does not function. The display is working and I took it apart, but I don't see any light to change. Kind of new to this stuff and would appreciate some help solving the problem
Just picked up a mint condition Rotel RCD-945AX for 20 dollars. Sounds real nice, but the backlight does not function. The display is working and I took it apart, but I don't see any light to change. Kind of new to this stuff and would appreciate some help solving the problem
dr*audio
Fish fingers and custard!
The backlight should be behind the LCD. Sometimes you have to de-solder and remove the display.
jeffpaletz
AK Subscriber
Technics SL-P2 still skipping
I have a Technics SL-P2. I've changed the belts that drives the sled and moves the CD tray back and forth. I've cleaned the rails and the screw drive and the plastic part that rides the screw drive and connects to the laser assembly. I've oiled the top of the drive spindle motor area and made sure the chuck is not not riding too low and rubbing on its holder. I cleaned the top of the laser lens with a damp eye glass cleaning cloth The CD player spins up and reads the TOC quickly on all disks with no issues and it also goes from track to track if you press the skip ahead or back buttons without any problems.
This CD player can play a few disks all the way through without skipping at all, consistently. However it skips on most disks anywhere on the disc. I really like this CD player because of how you can program tracks to play and it matches the rest of my silver faced equipment.
What else do you suggest I do?
Thanks in advance for your help and thanks for providing all this information on this forum.
I have a Technics SL-P2. I've changed the belts that drives the sled and moves the CD tray back and forth. I've cleaned the rails and the screw drive and the plastic part that rides the screw drive and connects to the laser assembly. I've oiled the top of the drive spindle motor area and made sure the chuck is not not riding too low and rubbing on its holder. I cleaned the top of the laser lens with a damp eye glass cleaning cloth The CD player spins up and reads the TOC quickly on all disks with no issues and it also goes from track to track if you press the skip ahead or back buttons without any problems.
This CD player can play a few disks all the way through without skipping at all, consistently. However it skips on most disks anywhere on the disc. I really like this CD player because of how you can program tracks to play and it matches the rest of my silver faced equipment.
What else do you suggest I do?
Thanks in advance for your help and thanks for providing all this information on this forum.
Last edited:
dr*audio
Fish fingers and custard!
When you cleaned the rails that the pickup slides on, what did you clean them with, and did you lubricate them, and with what?
jeffpaletz
AK Subscriber
Technics SL-P2
I used 91% isopropyl alcohol and used Lubriplate to relube the rails. I spent the last couple of hours cleaning off the Lubriplate with 91% Isopropyl Alcohol and used liquid bearings synthetic lubricant to relube the rails that the pick up rides on which solved the problem on short disks 45 minutes or less. It still skips on longer disks. I connected a digital meter to the motor that drives the screw drive and it shows voltage ranging from 0.68 to 0.86 though there are very short spikes that are shown on the analog scale that reach about 1.2 volts. They are so short that the digital display doesn't show them. When playing longer disks the analog portion of the meter spikes to 2.0-3.0 volts when it is skipping.
Why do you suppose longer disks skip only while playing the sections longer than 45-50 minutes? I opened up the unit and put more liquid bearing on the rails but that didn't help. I ordered a can of DuPont teflon silicon spray from Amazon today so it should be here on Thursday. Lowes was out of stock on it and I could not find it locally anywhere. Do you recommend that I clean off the rails again and spray the teflon silicone on the rails? Any other recommendations?
UPDATE: As of this morning it's skipping on most disks again.
I used 91% isopropyl alcohol and used Lubriplate to relube the rails. I spent the last couple of hours cleaning off the Lubriplate with 91% Isopropyl Alcohol and used liquid bearings synthetic lubricant to relube the rails that the pick up rides on which solved the problem on short disks 45 minutes or less. It still skips on longer disks. I connected a digital meter to the motor that drives the screw drive and it shows voltage ranging from 0.68 to 0.86 though there are very short spikes that are shown on the analog scale that reach about 1.2 volts. They are so short that the digital display doesn't show them. When playing longer disks the analog portion of the meter spikes to 2.0-3.0 volts when it is skipping.
Why do you suppose longer disks skip only while playing the sections longer than 45-50 minutes? I opened up the unit and put more liquid bearing on the rails but that didn't help. I ordered a can of DuPont teflon silicon spray from Amazon today so it should be here on Thursday. Lowes was out of stock on it and I could not find it locally anywhere. Do you recommend that I clean off the rails again and spray the teflon silicone on the rails? Any other recommendations?
UPDATE: As of this morning it's skipping on most disks again.
Attachments
Last edited:
dr*audio
Fish fingers and custard!
The sled voltage will rise like that until the sled moves and corrects the tracking error. The voltage should not be above 1V. Higher voltages either means the sled is binding somewhere, or the sled motor is bad. Remove the gear that drives the sled so you can move the sled back and forth freely and check for friction. It should flop back and forth by itself if you tilt the player. If not, keep cleaning and moving the sled back and forth until nothing comes off on the Q-Tip. Then lube it with a light oil a couple drops on the rails on each side of the pickup, then move the sled back and forth to spread the oil. then check the friction again.
If the sled moves freely, the motor is bad.
jeffpaletz
AK Subscriber
Any source for the motor? What is the part number? My sled flops back and forth with no problem. I have two of these with the same problem. What goes wrong with the sled motor? Is there a way to fix it?
Last edited:
dr*audio
Fish fingers and custard!
The brushes wear out. Fix it by replacing it. Best bet is to find a motor online somewhere that is the same physical size with the same dimension mounting holes, center to center. In most cases the part number is on the motor, and you can Google it. You want the lowest voltage motor you can find. There are 2 main motor manufacturers, Mabuchi and Matsushita that are commonly used. The Matsushita motors are crap. Mabuchis are better. If it's a Matsushita you probably won't be able to find that same motor and will have to replace it with a Mabuchi.
jeffpaletz
AK Subscriber
Any idea why some disks play fine and some don't and skip? Would the motor being bad cause that to happen? I ordered a couple of sled motors from partstore.com. They show them as out of stock but available as a special order. I'll be surprised if they become available though.
Last edited:
dr*audio
Fish fingers and custard!
There may be other issues that cause it to act differently with different discs, but the high sled voltage is a smoking gun. If you have a scope you can check the rf level to give you an idea of the laser output. Most players will have 1.25 - 1.5V P-P with a good laser and older commercial CD. Newer commercial CDs and CDRs have lower reflectivity.
Rotel 945 Backlight
Finally found the time to take it apart. I don't see and lights behind the LCD display. But there does appear to be enough room to mount a couple to LCD light bulbs. Would this work. When I shine my flashlight behind the display I can see the display or am I still missing something. Thanks![IMG_3493[1].jpg](https://audiokarma.org/forums/data/attachments/494/494809-e5b52090909015a0952e0c2f333e64af.jpg "IMG_3493[1].jpg")
![IMG_3494[2].jpg](https://audiokarma.org/forums/data/attachments/494/494810-66739dcf275db7c0f38acdc9c73e256a.jpg "IMG_3494[2].jpg")
Finally found the time to take it apart. I don't see and lights behind the LCD display. But there does appear to be enough room to mount a couple to LCD light bulbs. Would this work. When I shine my flashlight behind the display I can see the display or am I still missing something. Thanks
jeffpaletz
AK Subscriber
Technics SL-P1-P2 compatibility
I noticed that the mother board of the P1 and P2 have the same sockets to connect the front display and control panel. Even though the P1 doesn't have the ability to work with a remote or have the headphone jack and volume control the P1 mother board has the socket to work with these functions. When I connected the P2 front to the P1 chassis, the remote control works fine, the Headphone jack and volume control work fine, but the display does not light up. Any idea what needs to be done to make this work? The P1 is from December 1984 and the P2 is from August 1985. The mother boards look somewhat different though they have the same sockets. The P1 mother board is part number SRDPN001N21 and the P2 is SRDPN001N31. I don't know if that's because they are different models or because of a design change during the manufacture of these CD players.
I got a working SL-P1 CD player which I planned to put the disk playing mechanism into my P2. On the P1 mech I cleaned the old lube off using 91% alcohol, changed the belts and relubed it using the Teflon spray you recommended above. The disk mech works perfectly in the SL-P1 but skips when I put it into the SL-P2. I presume that there must be some adjustments that need to be made to get it to work property when it's placed in a different model player. I don't have the ability to make those adjustments.
I noticed that the mother board of the P1 and P2 have the same sockets to connect the front display and control panel. Even though the P1 doesn't have the ability to work with a remote or have the headphone jack and volume control the P1 mother board has the socket to work with these functions. When I connected the P2 front to the P1 chassis, the remote control works fine, the Headphone jack and volume control work fine, but the display does not light up. Any idea what needs to be done to make this work? The P1 is from December 1984 and the P2 is from August 1985. The mother boards look somewhat different though they have the same sockets. The P1 mother board is part number SRDPN001N21 and the P2 is SRDPN001N31. I don't know if that's because they are different models or because of a design change during the manufacture of these CD players.
Last edited:
dr*audio
Fish fingers and custard!
Just take the sled motor from the donor unit and put it in the old mechanism. That will be easier than trying to make something work that was not meant to, without having the proper test equipment. If it still skips then, replace the drive transistors for the sled motor. I had that happen on one of my Technics players.
jeffpaletz
AK Subscriber
I'm very reluctant to take the sled motor out of a perfectly functioning unit. I checked the service manual and the motherboard part number is the same as in the P1 even though the manual is for the P2. I also connected the P1 front panel to the P2 player and the P1 panel worked as it should. Any ideas on getting the P2 panel to work on the P1 player?
Last edited:
jeffpaletz
AK Subscriber
I spent the morning swapping the motor from the P1 to the P2. The P2 still skips so I put the motors back where they came from. P1 still works fine. P2 plays some disks fine and skips on other disks.
jeffpaletz
AK Subscriber
I don't own as oscilloscope but I can get access to one and help using it. What is the process for adjusting the Technics SL-P2 with an oscilloscope?
