I have a Revox B226 that powers up, tray mechanism works good, disk starts to spin up then stops before playing. After extensive forum research I am working my way down the list. Done so far:
Recapped all electrolytics
Reseated all IC’s and ribbon cables
Made small adjustments to the motor spindle Torx bolt
Let the machine warm up over an extended period
Cleaned the laser lens
Going to probe all regulated supply voltages today
Need to replace the L272M in the IC5 position
Some questions:
1) What do you guys use as a replacement for the discontinued L272M in the IC5 position?
2) what are the blue caps of death (BCOD)? Are they electrolytic or the blue non polarized caps?
3) How much of an adjustment are we talking about on the spindle height adjustment torx, 1/4 turn.....?
4) Can I see the eye pattern with a digital o scope? Does this apply if it does a short spin up but won’t start playing?
5) Any other ideas?
Thanks,
George
Recapped all electrolytics
Reseated all IC’s and ribbon cables
Made small adjustments to the motor spindle Torx bolt
Let the machine warm up over an extended period
Cleaned the laser lens
Going to probe all regulated supply voltages today
Need to replace the L272M in the IC5 position
Some questions:
1) What do you guys use as a replacement for the discontinued L272M in the IC5 position?
2) what are the blue caps of death (BCOD)? Are they electrolytic or the blue non polarized caps?
3) How much of an adjustment are we talking about on the spindle height adjustment torx, 1/4 turn.....?
4) Can I see the eye pattern with a digital o scope? Does this apply if it does a short spin up but won’t start playing?
5) Any other ideas?
Thanks,
George
4) The eye pattern can be easily seen with any cheap analogue ‘scope but in my experience only a really good digital ‘scope will show you eye pattern well enough to take measurements and make adjustments. Assuming your ‘scope can see the eye pattern you might catch a glimpse of it as the pickup tries to focus but I don’t think it will help you much.
First things to find out:
does the pickup arm move to the start position?
Does the laser turn on?
Does the lens try to focus?
Is the disc spinning at the correct speed to start?
The manual is as good as they get, Good luck!
First things to find out:
does the pickup arm move to the start position?
Does the laser turn on?
Does the lens try to focus?
Is the disc spinning at the correct speed to start?
The manual is as good as they get, Good luck!
Hi George,
Asimo is right. I had to get a Keysight MSOX3104T before I could see a usable eye pattern. You can get a mess of one on cheaper DSO's, but you are way further ahead with an analogue oscilloscope for that.
For reference, mine cost $25 K here in Canada (all software options unlocked). So I am not kidding.
I've done CD repair forever - since CDs came out. You can get yourself into a lot of trouble "recapping" equipment. Did you blow up the L272M by chance?
Don't know anything about a blue cap of death. Many people who write about repairs on the internet don't know what they are talking about and are complete idiots. I would respectfully suggest you get your expensive CD player into the hands of a really good audio technician. Not a computer repair guy, or TV repair guy. Someone who actually knows what they are doing. It will be cheaper than you causing damage. No offense, but you are not qualified to work on this equipment.
-Chris
Asimo is right. I had to get a Keysight MSOX3104T before I could see a usable eye pattern. You can get a mess of one on cheaper DSO's, but you are way further ahead with an analogue oscilloscope for that.
For reference, mine cost $25 K here in Canada (all software options unlocked). So I am not kidding.
I've done CD repair forever - since CDs came out. You can get yourself into a lot of trouble "recapping" equipment. Did you blow up the L272M by chance?
Don't know anything about a blue cap of death. Many people who write about repairs on the internet don't know what they are talking about and are complete idiots. I would respectfully suggest you get your expensive CD player into the hands of a really good audio technician. Not a computer repair guy, or TV repair guy. Someone who actually knows what they are doing. It will be cheaper than you causing damage. No offense, but you are not qualified to work on this equipment.
-Chris
I have 50 years of electronics experience designing, building and repairing amplifiers and related circuits. That said this is my first CD player.
One thing that is not clear to me is if the player needs to detect a cd in the transport to complete the start up sequence, track locking, focusing and reading the TOC.
The spin up rate is around 900 rpm.
The laser assembly does move into the inner track area at start up but its not very convincing, I can move it easily with my finger after it gets there.
With no CD in the transport the laser assembly does not start the vertical focus search process after the assembly travels to the inner track area.
I recorded a video of the laser at start up with my iphone in the dark and I did not see any output. I do not have a laser power meter. Again, no CD in the tray.
"Did you blow up the L272M by chance?"
Not that I know of. All of these problems are the same before and after the recap and power rail testing. Since the L272M is out of production, what do you suggest as a replacement?
No offense taken but I usually am not qualified on new projects because I love to learn new things and this project is no exception, been doing it for 50 years.
Thank you,
George
Hi George,
Fair enough, but CDs can be a little different than audio amplifiers. That said, most techs I run into don't even understand how amplifiers really work. It's scary out there!
Ignore the IC replacement until you know for sure you need one.
Okay, RPM near the center should be around 500 RPM. Normally, the sequence is home the laser head and pull back slightly, look for focus lock and lock the focus servo, spin CD and go for a recovered clock lock, lock the spindle motor servo (speed), then close tracking servos and read the TOC.
It sounds like you aren't getting a clear eye pattern, so your spindle motor never locks and it runs away. Focus lock does occur, but it might be off.
Adjustments normally are good enough for it to run unless someone has twisted pots. So the most likely issues are bad spindle motor bearing, or low laser power. On some players the spindle table can ride down the shaft, so resetting the height might fix it. The important thing to remember is that it is normally NOT an electrical adjustment. Leave the pots alone, especially the laser power control (APC). That is typically on the head.
-Chris
Fair enough, but CDs can be a little different than audio amplifiers. That said, most techs I run into don't even understand how amplifiers really work. It's scary out there!
Ignore the IC replacement until you know for sure you need one.
Okay, RPM near the center should be around 500 RPM. Normally, the sequence is home the laser head and pull back slightly, look for focus lock and lock the focus servo, spin CD and go for a recovered clock lock, lock the spindle motor servo (speed), then close tracking servos and read the TOC.
It sounds like you aren't getting a clear eye pattern, so your spindle motor never locks and it runs away. Focus lock does occur, but it might be off.
Adjustments normally are good enough for it to run unless someone has twisted pots. So the most likely issues are bad spindle motor bearing, or low laser power. On some players the spindle table can ride down the shaft, so resetting the height might fix it. The important thing to remember is that it is normally NOT an electrical adjustment. Leave the pots alone, especially the laser power control (APC). That is typically on the head.
-Chris
Since the laser assembly does move to the inner track area and the disk starts spinning it must have achieved focus lock but then the disk speed is incorrect so there is no disk motor servo lock or it locks to an incorrect rpm.
Can the laser power be marginal such that the player can focus but then not read the disk data for spindle motor and/or tracking servo lock?
Can this behavior be associated instead with tracking lock so the laser is focused and does have enough power but cant read the data for motor servo lock because it cannot track and hence cannot read data?
Thanks,
George
Can the laser power be marginal such that the player can focus but then not read the disk data for spindle motor and/or tracking servo lock?
Can this behavior be associated instead with tracking lock so the laser is focused and does have enough power but cant read the data for motor servo lock because it cannot track and hence cannot read data?
Thanks,
George
When the IR light output from the laser is too low the most frequent symptom is total failure to achieve focus lock. This usually results in a “no disc” indication from the system control MCU, putting the player into “stop” mode. The MCU in some players may be programmed to rotate the spindle motor a few turns during the focus search. This behavior usually appears to be somewhat “lazy” in comparison the the rapid acceleration in RPM that usually occurs when everything is working right. Direct side-by-side comparison to a working CD player is often useful.
When focus lock is achieved then the spindle motor is commanded to start rotating. If the spindle motor is faulty it may not be able to achieve sufficient RPM for the player to reach the CLV (constant linear velocity) phase-locked state. Faulty spindle motors are a common problem in low-cost consumer-grade players with a tiny DC spindle motor that uses a commutator & brushes. That said, the elaborate brushless spindle motors in high-end players can also develop problems.
Is the disc spinning slower than normal? Or faster than normal?
(when compared to a working CD player)
The spindle motor must be capable of rapidly accelerating the disc to a speed somewhat faster than 500 RPM for a brief length of time just after focus lock is achieved. Then it should settle to steady RPM close to 500 RPM and next there should some small “back and forth” motions of the carriage as the controller locates and reads the TOC data from the beginning of the disc. When everything is working the playing time of the disc & number of tracks should appear on the player’s display at this time.
When the disc is rotating there should be some RF signal (eye pattern). Observing the eye pattern with an oscilloscope is the best thing to do next when the player will get to this point where the disc is rotating.
-EB
The laser goes to the inner track home position but it’s not held there very forcefully, I can easily move it along the radial arc.
I can’t see that the laser is on even with a close up video with my phone. I am building a simple photodetector circuit just to verify that it turns on.
I have seen it hunt for focus but not every time or the vertical travel is so small that I don’t see it reliably
The disk starts spinning and continues for around 10 seconds and the rpm ramps up to around 900 before it quits. It does not read the TOC.
I only have DSO’s so I can’t look at the eye pattern. I am studying the service manual and getting ready to start probing some test points. I recapped all of the electrolytics.
My conclusion so far is that the player cannot achieve track/radial servo lock.
George
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Hi George,
The laser can in fact be weak enough to achieve focus lock, but not strong enough to provide an eye pattern that it can lock to. The expected laser output power is typically around 0.080 mW, three beam systems run around twice that. I have a laser power meter that I have used since just after CD players came out in case you were wondering. This is real life observations, not reading on the internet.
Sometimes the flex cable can go intermittent. The head is positioned weakly to the area near the spindle motor. The fact that you can move it easily merely means the tracking servo is not locked (no surprise here folks).
The eye pattern is like a blood test. It speaks volumes about what is going on. You really need to observe the eye pattern and maybe take a picture of it. Beg, borrow or steal (kidding) an analogue oscilloscope. You need 0.5uS/div horizontal, vertical sensitivity should be no problem on any scope. Most dual trace, 20 MHz oscilloscopes will be able to display the eye pattern.
I had two 'scopes on my bench for years. One DSO and one analogue. My need for the analogue 'scope disappeared when I bought my Keysight MSOX3104T (freaking expensive!!!!), but it takes that level of DSO to observe an eye pattern. Any of the DSOX3000 series 'scopes should be fine for this. Having said that, my analogue 'scope is still better for looking at an eye pattern. The very best 'scope I have seen for looking at eye patterns are the Philips, or Fluke-Philips 'scopes. Better than Tektronix, I used a Philips PM3070 and also a PM3065. The only negative thing I can say about those 'scopes is that when they are turned on, FM tuners have a hard time.
Keysight recently came out with an EDU series of instruments (4 to be exact). I won a power supply, but I want to see a 'scope to check out how useful it is. I'll report back once I have had a chance to run it through some paces. I always test a CD eye pattern when I check out a new 'scope.
All:
You should check out this series of equipment, and the 1000X series of 'scopes. The EDU meter and function generators are packed with features and high quality performance. You really get a lot for the buck with these. The power supply is very low noise and has very useful ranges, which is why I selected it. It will replace an HP 6236A I've had since the 1970's that still works extremely well. I think I can make a case for an upgrade though.
Anyway George, in a nutshell. You really need to observe and maybe take a picture of a clear eye pattern. The eye pattern can be a mess, but we need a shot of a clean trace showing whatever. My bet is that the amplitude is too low.
I do remember one fault on these. The suspension for the lens sags. If you adjust it so it gets a focus lock, it will lose lock when it switches to the focus servo. You said you adjusted that setting. You may be set wrong now and the original fault may have been the sagged suspension. You should never touch adjustments. Figure the CD player was working at one time with the adjustments the way they were. Messing with adjustments merely gives it another reason why it doesn't work. Please return that adjustment to close to where it was and try again. I know for a fact that you can adjust it to a point where it will lock to the CD surface, then lose that lock when the servo switches on. I have done it myself years ago (in the 1990's). The fix? A new transport. I was doing overflow work for Studer/Revox at that time and had access to everything. The new CD mechanism did fix the problem and I was told that it was one failure mechanism for that transport.
I guess you could store it upside down for some years to restore it. No idea how long that would be. I hope that isn't your problem.
-Chris
The laser can in fact be weak enough to achieve focus lock, but not strong enough to provide an eye pattern that it can lock to. The expected laser output power is typically around 0.080 mW, three beam systems run around twice that. I have a laser power meter that I have used since just after CD players came out in case you were wondering. This is real life observations, not reading on the internet.
Sometimes the flex cable can go intermittent. The head is positioned weakly to the area near the spindle motor. The fact that you can move it easily merely means the tracking servo is not locked (no surprise here folks).
The eye pattern is like a blood test. It speaks volumes about what is going on. You really need to observe the eye pattern and maybe take a picture of it. Beg, borrow or steal (kidding) an analogue oscilloscope. You need 0.5uS/div horizontal, vertical sensitivity should be no problem on any scope. Most dual trace, 20 MHz oscilloscopes will be able to display the eye pattern.
I had two 'scopes on my bench for years. One DSO and one analogue. My need for the analogue 'scope disappeared when I bought my Keysight MSOX3104T (freaking expensive!!!!), but it takes that level of DSO to observe an eye pattern. Any of the DSOX3000 series 'scopes should be fine for this. Having said that, my analogue 'scope is still better for looking at an eye pattern. The very best 'scope I have seen for looking at eye patterns are the Philips, or Fluke-Philips 'scopes. Better than Tektronix, I used a Philips PM3070 and also a PM3065. The only negative thing I can say about those 'scopes is that when they are turned on, FM tuners have a hard time.
Keysight recently came out with an EDU series of instruments (4 to be exact). I won a power supply, but I want to see a 'scope to check out how useful it is. I'll report back once I have had a chance to run it through some paces. I always test a CD eye pattern when I check out a new 'scope.
All:
You should check out this series of equipment, and the 1000X series of 'scopes. The EDU meter and function generators are packed with features and high quality performance. You really get a lot for the buck with these. The power supply is very low noise and has very useful ranges, which is why I selected it. It will replace an HP 6236A I've had since the 1970's that still works extremely well. I think I can make a case for an upgrade though.
Anyway George, in a nutshell. You really need to observe and maybe take a picture of a clear eye pattern. The eye pattern can be a mess, but we need a shot of a clean trace showing whatever. My bet is that the amplitude is too low.
I do remember one fault on these. The suspension for the lens sags. If you adjust it so it gets a focus lock, it will lose lock when it switches to the focus servo. You said you adjusted that setting. You may be set wrong now and the original fault may have been the sagged suspension. You should never touch adjustments. Figure the CD player was working at one time with the adjustments the way they were. Messing with adjustments merely gives it another reason why it doesn't work. Please return that adjustment to close to where it was and try again. I know for a fact that you can adjust it to a point where it will lock to the CD surface, then lose that lock when the servo switches on. I have done it myself years ago (in the 1990's). The fix? A new transport. I was doing overflow work for Studer/Revox at that time and had access to everything. The new CD mechanism did fix the problem and I was told that it was one failure mechanism for that transport.
I guess you could store it upside down for some years to restore it. No idea how long that would be. I hope that isn't your problem.
-Chris
900 RPM is fast enough. This suggests the spindle motor is OK
Having the disc continue to spin for 10 seconds is a sign that the controller is attempting to read the TOC data from the disc. It wouldn’t spin the disc for 10 seconds if there was no detectable RF signal. It really is necessary to view the RF signal eye pattern with a ‘scope. I have both digital & analog oscilloscopes. It wasn’t terribly difficult to fiddle with the settings of my DSO sufficiently to get a usable display of a CD player eye patterns. They don’t look precisely the same as the display on an analog ‘scope. But the DSO is more than good enough to diagnose issues with amplitude, noise, & excessive jitter.
In my opinion this is a tracking isssue. Some items that will help with diagnosis:
Is the rotational RPM constant or does it vary constantly during those 10 seconds of spindle rotation?
What does the laser carriage do during this 10 seconds of motor operation?
Does it move?
If it does move, how large are the movements?
Does it swing all the way across the entire disc?
Does the disc transport make clicking sounds?
-EB
I fully agree. From my previous incarnation as an audio repair shop owner, I confirm that a laser power meter is a valuable tool. Especially for the restoration of vintage CD players. There’s 100’s of posts about “bad laser diodes.” But there’s no substitute for measuring the actual mW of IR light produced by the laser pickup. Another critical item to measure is the laser current (Iop) when attempting to adjust the mW level of light output. I’ve fixed CD players which were totally unable to initialize a disc by a 5 degree rotation of a laser APC trimpot. While monitoring both Iop and uW of light I rotate the trimpot in tiny increments. So far I haven’t destroyed any laser diodes. But I confirmed which laser diodes were bad and which were still perfectly good. There are plenty other things which can prevent an optical pickup from functioning. That said, confirming proper uW light output from the optical pickup is crucial.
I’m restoring an Onkyo DX-120 which failed at the focus search. I measured <150 uW from its TAOHS-style optical pickup. Service manual states >250 uW is required for proper functioning. I raised it to 275mW. Now the machine initializes discs & plays them. RF signal is 2.8V P-P. This is close to service manual value of 3V P-P.
I will soon be posting eye patterns from my Onkyo DX-120 CD player.
I may have identified a case of “sagging suspension” in my Onkyo DX-120. Follow-up will be in my Onkyo DX-120 thread.
-EB
Hi EB,
Your Onkyo needs a new laser head. Never play with the APC control - ever!! You can do it to diagnose a bad head in marginal situations, but the head will fail soon once the current is increased. Also, you will hit a value where the laser diode fails, and does so suddenly. Also, you are allowed a 10% increase in Iop due to use (wear), above that the head is considered to be past it's useful life. (read bad).
Wannabe service techs read this stuff and I have seen several machines where the "tech" turned up the laser power and charged the customer for the "fix". I have also seen good heads killed by idiots playing with this control. If there is any hard and fast rule, do not touch the pots mounted on a laser head.
Good luck with your machine, but you do need a new head. Please do not ever breathe the fact that you touched the APC control. Idiots will head for it in droves and I'll see a bunch of machines needing heads where they wouldn't normally.
-Chris
Your Onkyo needs a new laser head. Never play with the APC control - ever!! You can do it to diagnose a bad head in marginal situations, but the head will fail soon once the current is increased. Also, you will hit a value where the laser diode fails, and does so suddenly. Also, you are allowed a 10% increase in Iop due to use (wear), above that the head is considered to be past it's useful life. (read bad).
Wannabe service techs read this stuff and I have seen several machines where the "tech" turned up the laser power and charged the customer for the "fix". I have also seen good heads killed by idiots playing with this control. If there is any hard and fast rule, do not touch the pots mounted on a laser head.
Good luck with your machine, but you do need a new head. Please do not ever breathe the fact that you touched the APC control. Idiots will head for it in droves and I'll see a bunch of machines needing heads where they wouldn't normally.
-Chris
Understood.
I do suspect this optical pickup of having issues. In fact it may have more than one issue. That said, I'm listening to it right now. It is now playing clean unscratched discs perfectly.
It's been a while since I've had a CD player with one of these TAOHS optical pickups on my workbench. The service manual refers to it as a TAOHS-DG2. But there's only a serial number and factory Iop/uW label on the pickup itself. This pickup looks different than other TAOHS pickup photos on diyAudio. There seem to be quite a wide array of different mounting options. Maybe that's what all the different suffixes (like -DG2) are about.
I do recall replacing these TAOHS-series pickups back in the day, sometimes while the CD players were still in-warranty. Onkyo wasn't the only brand to use them.
My Onkyo DX-120 restoration thread will get updated as I progress with it.
-EB
Excellent choice.
I have four CD players with Philips swing-arm optical pickups sitting next to my workbench. When time permits (hopefully very soon) I will test them and post photos of their eye patterns.
-EB