I agree with you, which is why I said for people to check that in the first post. I have seen one bad CDM-2 (which I unfortunately threw away), but that one may have had bad optics (the focus assembly had problems).
Even still, the CDM-0s and CDM-1s are getting very old, and I'm hoping there'll one or two out there.
Even still, the CDM-0s and CDM-1s are getting very old, and I'm hoping there'll one or two out there.
Laser diode position is only one of the factors though as the photodiode pickup array has to be precisely aligned to the laser, and in all the Philips CDM's I've seen the array looks like it has been positioned in a jig (to match the specific laser diode fitted) and then glued in place.
I think that may have to do with the way CDRs are written by some software, and the firmware in the player, rather than the CDM-0 mechanism.
The redbook requires 2 full seconds of P-subcode flag before the start of a track, not all cd writing software adheres to this.
My Grundig CDM-0 and CDM-1 play CDR without fail. Never skip, never slow to seek.
That certainly sounds like a valid theory, and it is something I had considered. This is why I want to try it on mechs with worn out lasers, where there is nothing to lose.
I guess this could be the case, I can't disprove it. However, my CDM-0 based player has read every CD I've asked it to. I suspect is more likely tired servo electronics.
Hi
I have two cd-players Yamaha CDX1100 and CDX910 which, problem is the laser, in both cdp's cd's are not spinning. I have look everywhere to buy new pickups but no luck.
My question is, can these lasers which you are mentioning can fix them by replacing only laser in the pickup??
I would like to try by changing the laser at least on 1100, because should sound better than my players I already have.
regards
bekim
I have two cd-players Yamaha CDX1100 and CDX910 which, problem is the laser, in both cdp's cd's are not spinning. I have look everywhere to buy new pickups but no luck.
My question is, can these lasers which you are mentioning can fix them by replacing only laser in the pickup??
I would like to try by changing the laser at least on 1100, because should sound better than my players I already have.
regards
bekim
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Are you sure it's the lasers that are at fault? Have you seen any data to suggest that the laser mechanisms of either player use the particular laser diode this thread is about?
Hi
with cdx910 for sure is laser 100%, even a friend who is expert on cdplayers confirms. But, even with the 1100 he told me that laser is fore sure, light is very dim...
I don't know laser you have will fit on these players, I'm trying to find in Europe supplier for lasers, and no luck so far. Everything with lasers directs me to Asia.
Yamaha CDX1100 has MLP7 pickup, I still didn't disassemble it to see what kind of laser has.
Yamaha CDX910 has TAOHS-JP3 pickup, same case, I didn't disassemble it yet..
I was looking to find pickups, this is the reason..
thanks
bekim
with cdx910 for sure is laser 100%, even a friend who is expert on cdplayers confirms. But, even with the 1100 he told me that laser is fore sure, light is very dim...
I don't know laser you have will fit on these players, I'm trying to find in Europe supplier for lasers, and no luck so far. Everything with lasers directs me to Asia.
Yamaha CDX1100 has MLP7 pickup, I still didn't disassemble it to see what kind of laser has.
Yamaha CDX910 has TAOHS-JP3 pickup, same case, I didn't disassemble it yet..
I was looking to find pickups, this is the reason..
thanks
bekim
Hi!
I'm a fan of the old Philips CD players and would be very interested in learning how to revive old CDM0 and CDM1 lasers. They don't fail very often but I've got a couple that don't work.
Only problem is that I'm not sure it's the laser that's dead - most of the time, I can still see the red spot through the lens. I've tried replacing the capacitors but no luck reviving a dead one yet.
Would be very interested in working with you to see if we can learn something here!
I'm a fan of the old Philips CD players and would be very interested in learning how to revive old CDM0 and CDM1 lasers. They don't fail very often but I've got a couple that don't work.
Only problem is that I'm not sure it's the laser that's dead - most of the time, I can still see the red spot through the lens. I've tried replacing the capacitors but no luck reviving a dead one yet.
Would be very interested in working with you to see if we can learn something here!
@ bekim
Again, I have to ask; have you seen any data to suggest that the laser mechanisms of either player use the particular laser diode this thread is about? Otherwise, it's not really relevant to this thread.
@ khjen
The only certain way to tell if the laser is the problem is to eliminate all the other variables. I test a lot of CDM-2s and CDM-4s, and I have a dedicated loader / servo / decoder setup for testing each type. I know my test setups are more or less infallible, so if there is a fault, it must be the laser mechanism.
However, there are other things that go wrong with the laser mechanism apart from decay of the laser diode. You also have:
Again, I have to ask; have you seen any data to suggest that the laser mechanisms of either player use the particular laser diode this thread is about? Otherwise, it's not really relevant to this thread.
@ khjen
The only certain way to tell if the laser is the problem is to eliminate all the other variables. I test a lot of CDM-2s and CDM-4s, and I have a dedicated loader / servo / decoder setup for testing each type. I know my test setups are more or less infallible, so if there is a fault, it must be the laser mechanism.
However, there are other things that go wrong with the laser mechanism apart from decay of the laser diode. You also have:
- Failed focus drive. The objective lens should bob as it tries to focus on a CD. These do jam occasionally, the symptom will be that the mech won't focus (and hence won't read the TOC). Try bumping the objective lens free.
- Excessive friction in the RAFOC pivot. The symptom of this is that the mech will focus and often read the TOC, but not track. Try re-oiling the upper and lower RAFOC bearings, and check the RAFOC is not being fouled by something (ribbon cable, etc).
- tried it in a known good system,
- adjusted the focus offset and laser current correctly,
- checked the RAFOC swings freely, and
- checked the objective lens is moving
The players with CDM-O/1 mechanisms all seem to support several firmware-selected service modes. (e.g. turning power ON while holding << and >>) This lets you check eyepattern and photodiode matrix signals without the variations introduced by the servos.
One other fault I have found is the rubber end-stop perishes, then the laser doesn't 'park' in the TOC area of the disc anymore - it goes too close to the centre hole and tries to do a Fucus Lock there - which fails. You can just stick in a tiny piece of thin rubber sheet to fix it.
One other fault I have found is the rubber end-stop perishes, then the laser doesn't 'park' in the TOC area of the disc anymore - it goes too close to the centre hole and tries to do a Fucus Lock there - which fails. You can just stick in a tiny piece of thin rubber sheet to fix it.
D'OH! I just saw that, and too late to do an edit now. I have not now, nor ever had, any affiliations to seaweeds.
amc184:
How do you adjust the laser current? It is controlled by the servo and depends on the reflected light from the CD. The laser, CD, photodiodes, servo make up a closed loop system. The laser current depends eventually on the reflectivity of the CD itself, and there are big variations. I checked it with several commercial CDs. There are two variants: the pits on the silver CDs are covered with aluminium, and the gold coloured ones are covered with gold as far as I know. Even the aluminium CDs exhibit big variance from sample to sample. Gold CDs have much more relectivity. And there are the organic composed rewritable CDRWs, they exhibit rather low reflectivity. One needs a reference CD with controlled reflectivity for proper adjustment of the laser current. Do you have such reference?
How do you adjust the laser current? It is controlled by the servo and depends on the reflected light from the CD. The laser, CD, photodiodes, servo make up a closed loop system. The laser current depends eventually on the reflectivity of the CD itself, and there are big variations. I checked it with several commercial CDs. There are two variants: the pits on the silver CDs are covered with aluminium, and the gold coloured ones are covered with gold as far as I know. Even the aluminium CDs exhibit big variance from sample to sample. Gold CDs have much more relectivity. And there are the organic composed rewritable CDRWs, they exhibit rather low reflectivity. One needs a reference CD with controlled reflectivity for proper adjustment of the laser current. Do you have such reference?
Oshifis- You are quite correct regarding how the philips servo controllers operate. This is why, whenever I do a laser current adjust on a radial arm tracking CDM, I use a large number of cd's & cd'r's & shoot for the best middle ground on the current. I believe trying to get a CDM-0 thru CDM-9 to play cd-rw, though, is unrealistic, and I don't think it's possible to get cd-rw play without hurting ability to play cd, unless you are very lucky.
I tested a bunch of CDs, and found one that was about average. I've then adjusted all the mechs I've worked with using that CD.
You can get the benchmark CDs, but they sound expensive, and I wouldn't know where to get one. Maybe one day...
As the service manual says though, it's 50mV +/- 5mV, so the value your adjusting to isn't that precise. I always adjust to exactly 50mV, so even if the reflectivity of my CD is a bit off, I'm likely to be in the correct range.
You can get the benchmark CDs, but they sound expensive, and I wouldn't know where to get one. Maybe one day...
As the service manual says though, it's 50mV +/- 5mV, so the value your adjusting to isn't that precise. I always adjust to exactly 50mV, so even if the reflectivity of my CD is a bit off, I'm likely to be in the correct range.
The laser current is totally independant of the CD. This is such a fundamental point it needs clarifying.
The laser diode, the LT022C has an inbuilt photo diode on the same die as the laser that monitors the OPTICAL output of the laser. The APC (automatic power control) loop keeps the OPTICAL output from the laser constant. The CD has no bearing on this.
The confusion comes from setting the power by monitoring the "current" from the photo diode array. You are setting the laser power BY REFERENCE to the reflected signal. Remove the CD and the laser power is still set at that same level.
If the laser current had been detemined by the reflectivity of the disc, which it isn't, then any CD would produce a similar photodiode current as the power would compensate automatically. I have often though this would be an ideal situation but in practice is fraught with difficulty. The laser would have to operate within safe limits, no reflected light (no CD) and the power would try and increase destroying the laser. Remember laser diodes can be destroyed in a matter of pico seconds with current spikes and that is one reason the power is monitored as it is on the die itself.
Other manufacturers used to recommend a "laser power meter" ... a calibrated photo diode and meter basically to monitor the "light" emmited from the objective lens.
Yes, there is so much misinformation regarding laser power. Leader made an excellent LPM which incidentally is incredibly simple in concept and design. I have the schematic someplace. I ended up making a simple LPM using polycrystalline solar cells from a solar powered wrist watch separated into individual 3mm square cells and an old VU meter. It did the job quite well.
🙂 Our service dept had to have a LPM to gain full Sony service "status" in the early days. TBH it was never really used... the quality/amplitude of the RF output viewed on a scope was always the deciding factor and with KSSxxx types perhaps a confirmation of the laser diode current which was always quoted as part of the pickup serial number. If you had to turn up the power to get RF at the correct amplitude and the optics were clean then the thing was failing anyway and would need replacement sooner or later.
What concerns me with replacing the diode on the Philips is whether the alignment is critical to obtain maximum "emmited light" from the objective lens. It's no good having it all apparently working OK if the laser is running at a higher than normal power. This isn't meant to discourage anyone from trying, just something to be aware of... and perhaps test by keep reseating the diode and see if the RF output and "quality" (the photodiode array current that Philips recommend you monitor) fluctuates at all while keeping the laser power adjustment untouched. Maybe even rig one up with a homemade meter as restore-john suggests and try it.
What concerns me with replacing the diode on the Philips is whether the alignment is critical to obtain maximum "emmited light" from the objective lens. It's no good having it all apparently working OK if the laser is running at a higher than normal power. This isn't meant to discourage anyone from trying, just something to be aware of... and perhaps test by keep reseating the diode and see if the RF output and "quality" (the photodiode array current that Philips recommend you monitor) fluctuates at all while keeping the laser power adjustment untouched. Maybe even rig one up with a homemade meter as restore-john suggests and try it.
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I fully realise that the laser supply is controlled by feedback from the integrated monitor diode. I thought the the reflectivity of the CD being read effected the response of the monitor diode somewhat, by picking up both the reflected and direct light. I stand corrected, that's what the forum is for.
The fact is, at least on the CDM-2 (which is the only mech I have been able to dissect in detail), you cannot 'align' the laser diode. It has a land that it is glued into, but the glue is almost unnessesary, as it is a press fit. However, the photodiode panel can be aligned. That sounds like a trivial difference, but it means that the position of a new diode installed into a CDM-2 will be very close to the original one. From what I make of the datasheet, the positioning of the crystal wafer within the metal can package is actually very precise. The beam angles are not, but again, due to the physical design of the RAFOC, this should not matter.
So what I am saying is yes, the system was factory aligned, but I think it is possible to replace the diode without significantly altering that alignment.
We shall see anyway. I have been talking with khjen, and it looks like he's going to send me something.
I'm actually not sure if I agree. It depends on how much the life is reduced. These diodes last a long time at their nominal output, and they're not exactly expensive. Did you see how many I had in the photo?
The fact is, at least on the CDM-2 (which is the only mech I have been able to dissect in detail), you cannot 'align' the laser diode. It has a land that it is glued into, but the glue is almost unnessesary, as it is a press fit. However, the photodiode panel can be aligned. That sounds like a trivial difference, but it means that the position of a new diode installed into a CDM-2 will be very close to the original one. From what I make of the datasheet, the positioning of the crystal wafer within the metal can package is actually very precise. The beam angles are not, but again, due to the physical design of the RAFOC, this should not matter.
So what I am saying is yes, the system was factory aligned, but I think it is possible to replace the diode without significantly altering that alignment.
We shall see anyway. I have been talking with khjen, and it looks like he's going to send me something.
I'm actually not sure if I agree. It depends on how much the life is reduced. These diodes last a long time at their nominal output, and they're not exactly expensive. Did you see how many I had in the photo?