ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Back in 2012 on the old workbench forum, I (kind of) got my first CDX working. The unit required the door hinge fix on the eject switch side and I was able to get the CD player working for a short while. Then it started acting up (working intermittently). Resolving that it was an alignment problem with the hinge switches, I put the CDX up and worked on other projects. Later, I received a second CDX that had good hinges.
I spent the last week trying to get one good functioning CDX out of the two. I actually had the unit playing CDs for one night. The next morning, it wasn't working again.
So far, I have resoldered the griplets on the two main boards of the first CDX. The second CDX looks to be a later version and has nicer looking griplets. For now I haven't touched those.
The problem I am having right now is the CD motor spins all of the time. When the lid is open, I checked all of the switches and they measure as expected. Yet the motor spins. Two days ago the CDX unit started functioning correctly. I could turn power on, open the lid, observe the motor wasn't spinning, insert a CD, hit play and the unit would start right up. It sounded really good when it works. The next morning I turned the unit on, inserted another CD and was surprised the the motor was already spinning the platter. So it broke overnight.
So at various times I have seen both of my CDX main chassis operate correctly while, right now, they both behave the same and will not stop turning.
That makes me suspect the problem is common to both so it would have to be in the common pieces of my latest tests...which are the lid components: eject assembly, lid door motor assembly and control panel assembly. The only thing is - I have seen it work with those same components. Maybe a loose wire somewhere?
As I said earlier, the two switches on the door open motor assembly and the one switch on the door eject assembly appear to be operating correctly. I can measure continuity and open on the switches as the door hinges go through their travel.
I tested powering on both of my CDX chassis disconnected from everything else. I would have thought that without any connections to the switches or control panel, the motor would not spin the platter. But in both units, the platter starts turning.
Here is the service manual schematic for the motor stop. The laser switch in my test is disconnected. With power on the CDX, I measure 12 VDC between the two pins the switch closes.
In looking at the schematic and with the Laser Switch connector out, 63-2 and 63-1 are open. I thought that would prevent the motor from turning. With that connection off, I measure -5.8 to -6 VDC at 63-2 and +6 to +8 VDC at 63-1. The closing of the door will close the Laser Switch which joins those two voltage points. So with it open, the motor should not spin, right? I must be missing something here though...because both units measure the same here and behave the same.
Sounds very much like a rivet via fault or a cracked solder joint in the power supply area.It can sometimes be difficult to guess at what will happen in a circuit if one or more ground points are disconnected.
Martin
I'll have to just dig in deeper. I did measure some various signals and with nothing connected to the main chassis, I see a +6 VDC on the DO signal which is the state of the signal in Play mode. With everything disconnected, I would expect that signal to be low (not in Play mode).
Can you tell me if the platter motor should be off if the CDX main chassis is turned on by itself (no connections to the lid motor control board or control & display board)? If the connector for the laser switch inputs is removed, should a working CDX power up with the motor not running?
I agree with Martin John. And please do those ominous griplets. They are responsible for the strangest issues - from degraded or crackling audio to odd servo problems.
When you press PLAY, the motor will indeed turn immediately as the player is looking for the TOC. It will stop only if no CD is detected by the laser.
I say, do the solder job!
Jacques
I'm not sure what to make of this yet (will have to sleep on it) but I was able to manually coax the CDX into working. I suspected part of the problem is in the initialization of the laser head and the other logic that controls the motor. When the CDX is failing, the platter immediately starts spinning and I can see some up an down movement on the laser head (light pen?). To be able to put a CD in place, I have to disconnect power, open the door, insert the CD, then close the door. After that I can turn power on. At this point the CDX tries to read the CD, detects nothing and briefly displays a question mark. I began running these tests with the bottom of the CDX case removed. I have to add some support underneath so the laser mechanism isn't obstructed. This allows me to see what is going on since I have to have the lid in place to hold down the CD. I was able to see that the laser head wasn't moving. So I helped it along a little and that reset something. The motor came to a stop. I pressed play but the CDX didn't go into play mode. The motor also didn't turn. I have seen that before and it usually meant the worm gear controlling the door closed position needs adjusting. I did that, tried the play button as I adjusted and the CDX began playing. I ran through a few tracks then tried a test of ejecting the CD and reinserting it. That worked fine. The next test was to turn power off the CDX, then back on. I did that and the CDX started up okay.
The CDX is not fixed of course. I have been here before. When I had the CDX working a couple of nights ago it went through this same scenario where all of a sudden it got into the correct mode where it came up with the motor not turning and the laser head adjusting correctly to a CD.
Maybe there is a problem with the laser head control. Something in the timing of things during start up? Could the laser sometimes stop in a position it can't start correctly from? Is the problem a mechanical adjustment problem on the laser head?
One of my next steps is to repeat the test tomorrow with the same CDX chassis I got working tonight. Then try the other CDX chassis and see if the same coaxing can get it playing again. I know it also works because I also had it playing a CD a few days ago.
chartz: I agree with Martin John. And please do those ominous griplets. They are responsible for the strangest issues - from degraded or crackling audio to odd servo problems. When you press PLAY, the motor will indeed turn immediately as the player is looking for the TOC. It will stop only if no CD is detected by the laser. I say, do the solder job!
In one of my earlier posts in this thread I mentioned that I had reworked the griplets on the two boards of my first CDX unit. That didn't help.
Regarding the start up - Keep in mind, the motor starts turning with the CDX door open. I don't think it should do that. You can't insert a CD with the motor spinning. When I have got the CDX into working mode, I can see the unit start with the motor not turning. To help trouble-shoot the problem, I expected the CDX to start with the motor not turning if I turned it on with no cables connected (to the door motor, laser switch, load switch, control and display panel). If none of those things are present, I would expect the motor to not start and the laser head not to look for anything. That doesn't appear to be the case though as both of my CDX units behave the same.
If it moves the laser lens up and down to seek focus, the lid contacts or related circuit is not working correctly.
Dillen: If it moves the laser lens up and down to seek focus, the lid contacts or related circuit is not working correctly.
Yes, it's a possibility indeed. But on both machines? What are the odds?
Have you tried re-assembling the thing?
I am using the same lid components on both CDX units during this testing. Earlier, I measured continuity on the three lid switches (laser switch, lid switch and load switch). I put my continuity meter leads back on the connectors receiving the signals and exercised the lid to see the switches open and close. The first time (couple of days ago) that I got the CDX to work I had been probing around the load switch. So maybe that is the culprit. I don't think it is the laser switch because I can disconnect the connector for that switch and it does not prevent the motor from running or the laser from trying to focus. I have used deoxit on those switches and they look clean. On the side with the door motor, laser switch and lid switch, I did take that apart as I had to replace one of the gears. I didn't disassemble the eject mechanism as it works good (mechanically). However, I can go through them again.
Update - as expected, the CDX is not working now after sitting for a few hours. It's very strange how it can kick into working mode and be fine for a while, then stop. That kind of points towards something that warms up and cools down. I may have to just take one of the CDX chassis and re-solder everything. That's also why I was wanting to know how the main unit should start up if none of the switches or control panel are connected. If it is switch related, then with the switches disconnected, shouldn't the main CDX unit think the door is open and start up in an "off" state? Why does the laser head try to look for a CD when the laser switch is open (disconnected)?
It's a goofy machine.Maybe a little cooling spray could help locate an eventual thermal fault.
Dillen: It's a goofy machine.Maybe a little cooling spray could help locate an eventual thermal fault. Martin
I agree, it is goofy. If I hadn't already heard it and liked its performance (when working), I probably wouldn't mess with it. But...I have heard it and I like the way it sounds and looks. Do you know what the motor and laser head should do when the unit is turned on with the lid removed (no lid switches or control panel)? If I knew for sure that the unit should come up with everything off, then I could troubleshoot just the main assembly electronics without the lid connected. it's kind of a pain with the lid in the way.
This afternoon I decided to run a couple more tests.Using the CDX main chassis I have been focused on (the one I had working yesterday), I verified it still doesn't work correctly with the lid and all connections in place.Next, I disconnected and remove the lid completely (again) and verified the platter motor turns when power comes on.
Adding something different to the test, I connected up the other CDX lid (and control/display board). That means a different set of switches (lid, laser, load). Another thing about this set of lid components - the door motor assembly is disassembled because I pulled the bad gear. I went ahead and wired everything up to the CDX main chassis, then turned it on. The same problem is there. With this new set of switches, I can manipulate them manually very easy as they are exposed. I was unable to find a combination of the switches that would affect the platter motor. It just keeps turning.I also noted that when I turned on power, the laser head would try to focus.With that test over, my next step was to switch out the CDX main chassis with the other one (my first one and the one where I re-soldered the griplets).I first noted the same behavior where the motor comes up turning immediately when power is applied and nothing connected to the chassis (no lid components). It behaves the same as the other one.
Now I connected up the lid components. I got the same result of the motor always spinning but I notice on this combination of components that the laser does not try to focus at start up, with the lid open like the other chassis did.
Here is a picture of this crude test set up. In both set of tests, the CD interior light functions in response to the door lid switches opening and closing.
I decided to dig in and measure what the CDX turntable motor control voltage is.
In observing the turntable motor as I powered the CDX on and off (with no lid components attached), I can see that sometimes the motor turns clockwise, sometimes it turns counter clockwise and sometimes it starts out stopped for a second or two...then turns clockwise.So checking the voltage at the motor control at the Pre Amp + Laser PCB, I measure +5.053 VDC when the turntable goes clockwise (looking from the bottom of the CDX) and -5.841 VDC when it goes counter clockwise. For the brief, occasional times the motor doesn't turn, I measure 0.285 VDC.
Here is a picture of the typical mode it starts up in.
From the Pre Amp + Laser PCB I traced back to the Servo board circuit that drives it. I am not sure why the CDX motor starts up in different states other than it could be due to none of the lid components being attached. I would think that the logic would be to not allow the motor to operate if the lid components were not connected. I will re-measure these nodes tomorrow with the lid in place. However, in my earlier trouble-shooting, I observe the motor turning all the time when the lid is attached...so it will be interesting to see.
Here is the schematic showing the servo circuit that controls the turntable motor. I have put in red, the voltages I measure at those places when power is on the CDX and no lid components are connected.
I re-measured the CDX turntable motor control circuit with both lids and both main chassis assemblies today. Here is a new picture of the schematic with the voltages from the other CDX assembly. There are differences in the voltages but the result in both cases is the same - the turntable motor is always in turn mode. I am thinking that both CDX units have their own problem that affects the motor drive. During these tests, I can see that the CDX logic it responding to the door hinge switches and I have tested two sets of door hinges. So I think the problem is somewhere in the main chassis assembly. On the schematic, it shows some expected values. The values that are circled are for the Stop condition. The values in a rectangle are for Play. My CDX units are supposed to be in the Stop mode, but stopped as in stopped with the lid open. The schematic may be describing Stop for a CD inserted with the door closed. The Stop I am looking for should produce a voltage at 23-5 between about +-1.2 VDC. That what I observed when the motor came up stopped a couple of times. I wasn't able to reproduce that condition today though. However, I can see that the motor will start turning as soon as it gets +5 or -5 across 23-5 and 23-6. I guess the next step is to start looking at the signals that feed pins 5 and 6 of the MC1458 OpAmp.
After looking at those last measurements something didn't look right to me so I re-measured them. The update shows the CDX 002 (as I have named it) with voltages that are in line with the schematic listed values. Those are the Stop mode voltages but are the same on this unit regardless of the position of the door switches.
The control voltages on the Servo board for the turntable motor look pretty much like they should except for the final output at 23-5 (+5.071 VDC). That should be down under 1 volt I believe. So if the controls for those signals leading up to the 6209 OpAmp are in the correct states, then the motor control problem must be elsewhere. I decided to look at the Motor Stop signals on the Servo board to and from the Motor Stop board. I had originally looked at the Motor Stop board first because it made sense that it would control the stopping of the motor. On my first look I couldn't see how that worked. So I measured the voltages on the CDX involved in the turntable motor and the Motor Stop board.Here are the signals on the Servo board. I get the same voltage values with the lid open or closed.
Here is the Motor Stop board with the measurements there.
With the measurements I have made, it doesn't make sense to me why the CDX is putting the turntable motor in that turning state. The are other lines ___ ___ like DO that go from Motor Stop 64-1 and Servo 29-1 to Servo 29-3 and on to Decoding 33-3. The CDX Circuit Description Manual does say that DO is used to determine if the motor is actually stopped or not. My measurement shows that it is high, so it is in Play mode.At this point I concluded that the problem is in the logic of the boards somewhere difficult to find. My decision now is to go ahead and re-solder the griplets of this CDX (CDX 002) unit. I had done that on the first unit and not had any success. But I decided it was the easiest thing to try at this point before going any deeper into the board. The boards on the CDX are a strange mixture of old, full-sized components soldered to the boards and tiny surface mount components. That makes trouble-shooting the components a little trickier. So, time to re-solder the griplets.
Okay Jacques and Martin....Apparently, the griplet re-soldering fixed the CDX. I did just the servo board first, it didn't fix the problem. Next I did the Decoder board. When I reconnected everything, there it was - the motor powers on stopped. The stopped voltage was less that a volt. I put the cover back on and tried a CD. The CD played.
This is a goofy piece of audio equipment for sure. I wish I had just soldered one griplet then tested before I moved to the next one. It would have been nice to know which part of the circuit was actually causing the problem.
Another strange thing was that I have two CDX units that fail in the same way (motor wouldn't stop spinning), yet the problem must be two separate issues with the main assembly. I thought that was not a likely scenario and the problem must be something common to both. That theory started falling apart when the problem remained regardless of what lid I used.
So I still have the second (CDX 001 in my earlier references) unit that I will put away for now until I get a door motor gear for it. On that unit I had already reworked the griplets but I guess I will have to retry that again. Of course there could be an actual failed component on the unit...but it had worked as recently as last week.I will see if this working unit (CDX 002) continues to work tomorrow.
FYI, here is what I measure on the Motor Stop board when the circuitry is working (CDX is on and the motor is not running).
Well done John. I admire your perseverance!
The vias or griplets I always do by inserting a piece of wire through the hole and solder on both sides. Just to be sure.
Philips CD104 machines (upon which CDX is based) suffer the same problem.
Thanks Jacques.I am happy to report the CDX is still working great today.
Today I went back an ran a circuit simulation of that motor control. I see now how that DO signal from the Decoding board controls the motor drive on the Servo board. So it makes sense why the griplet re-soldering didn't work until I did that (Decoder) board. Now I know if the turntable motor won't stop turning, the first thing I need to do is check the control signal (DO) from the Decoding board. That other CDX appears to have the same problem but I had already re-soldered those griplets with new wire through to connect the layers. That unit could still have a bad connection or some component actually failed. I'll take another look at the second CDX this weekend.For now though, I am enjoying the working CDX and I think is was well worth the effort to get the problem solved.
-sonavor
I dug back in to the other CDX unit (the one I refer to as CDX 001 because it was the first one I worked on).
This CDX 001 unit is the one I had already repaired the griplets on but behaves the same as my (repaired) CDX 002 unit. So the griplets should be fine. To double-check them I tested continuity between all of the griplets to each other and the ground plane as well as the trace side where the griplets connect to. No problems were found.
The next step was to power up the CDX and check the DO signal. Sure enough, it was high (+6.2 VDC). It should be low. I also checked right at the signal source (Comparator LM339N device), IC 6508 - pin 13. Checking the other 6508 pins I noticed that pin 5 was +7.5 VDC. It is supposed to be fixed at +2.5 VDC.
I decided to pull the 6508 chip and tie the pin 13 DO signal to the pin 12 (ground). That will make sure the DO signal is low and prevent the motor from turning. I observed it did nothing. The DO signal was still high.
I took the unit apart again and checked the 6508 pin 12 ground pin to the board ground. It should measure continuity with the griplets and ground plane. It didn't. Tracing the IC grounds around the trace side, I found that the IC grounds were connected between 6508 (pin 12) and 6501 (pin 14). 6501 pin 14 is supposed to connect to the griplet that is nearby it. When I checked for continuity between those two pins, I got nothing. I could see the board trace (less than 10mm) connects them but they aren't connecting. So I created my own jumper between the griplet pin and the 6501 pin 14 lead.
The CDX 001 unit now powers on with the motor off as expected. The Decoder board 6508 comparator chip has a low on pin 13 (output for DO) and the 6508 pin 5 signal is now back to +2.5 VDC as expected.
Jacques is gracious enough to send me a spare CDX door motor drive gear to replace the broken one on this unit. Once it arrives I will reassembly this CDX 001 unit completely and expect it to work.
Here is a picture of the schematic showing the CDX DO signal to the Motor Stop. The red circled area is where the missing ground caused problems for the DO signal.
Here is the CDX Decoder board repair I had to make to reconnect IC 6501, pin 14 (ground) with the griplet pin. The jumper is soldered to the IC pin. A better fix might be to install a 14-pin socket for IC 6501 and solder the jumper to the socket pin 14 (instead of the actual IC). But for now I will leave it like this and put this unit up until the new door motor gear arrives.
What I like and look up to John is that you actually do your repairs in a very insightful way, while we amateurs "just do the griplets" and pray. Most of the time, it works, but not always!
Thanks for your time and the invaluable illustrations and thorough explanations.
chartz: What I like and look up to John is that you actually do your repairs in a very insightful way, while we amateurs "just do the griplets" and pray. Most of the time, it works, but not always! Thanks for your time and the invaluable illustrations and thorough explanations.
I´m always following Johns threads, always interesting, thank you John
Collecting Vintage B&O is not a hobby, its a lifestyle.
Thanks for the comments Jacques and Søren. One great enjoyment of this forum is with the information members share as projects are worked. I like contributing as I learn about these old audio components. This really is about the only way a vintage audio enthusiast can learn about equipment that is long out of production. I am still very green when it comes to audio repair knowledge but I feel I have learned a lot in the last two or three years. Nothing beats getting hands-on and working with something.
Today I decided to see if I could go ahead and rig this CDX unit to play a CD. I was able to use my fingers to keep the disc secure as it started turning and accelerated to play speed. Sure enough, the laser read the disc and began playing. A very good sign. Here is a picture of the disc playing. One thing to note, when you operate the CDX with everything apart like I have it setup here, you must make sure to raise the main chassis off the surface so the laser mechanism underneath can move. I mention that because it may not be obvious in the picture that the chassis is raised off the table.
What a lovely picture! Good work as always John!
//Bo.A long list...
I would have guessed the top of the unit had to be engaged to play a disc.
No. CDM0 and CDM1 will play with no clamp!
This weekend I received the gear from Jacques for the CDX door.
Thanks again Jacques !
I see another thread on the Beoworld Forum that asks about Beoworld losing its mojo. When it comes to the workshop, this is really The Forum to come to. Whatever you call it (mojo, energy, activity), there is a really supportive group here and it is great to have. Maybe other areas of Beoworld feel like they have lost something but for repair questions this is it. As modern electronics gets more and more into micro, surface mounted internals, those pieces may end up too difficult for the "do it yourself" repair guys (like me) to work on. In the meantime, I think there are plenty of vintage repair units out there to keep me busy.
FYI - I don't have anything against modern entertainment systems. I just prefer the older stereo systems for listening to and working on.
Getting back on topic, here is the replacement gear from Jacques (in the bag) and the broken one.
Now for the reassembly.First the replacement gear so the belt can be attached to the motor.
Next, the main drive gear that operates the door hinge.Note: I had to loosen the Laser Switch to get the white gear in place.
The next step is to attach the door hinge.
Now the metal washer and C-clip for the white drive gear. I should have noted there is a small metal C-clip on the yellow replacement gear that Jacques sent as well.