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Old 1st March 2002, 10:17 AM   #1
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Default Philips CDM-1

I have just bought a reVox B226S and I was wondering how hard it would be to get spare part for the CDM-1 transport?

It isn't broken.... yet, but it is a cool transport that I would like to have a long life.
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Old 6th March 2002, 04:00 PM   #2
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Hello Flemming J P,
from memory think this is older type mech and laser assy.
Philips/Marantz were original supplier - Also other comsumer equipment parts suppliers.
Various model Phillips CDP mechs went into a lot of different audio systems - even Taiwan type 4in1 systems.
In servicing a lot (hundreds) of Philips and Marantz cdps,
I found overwhelmingly dry joints and mechanical faults before faulty laser assembly.
Common mechanical problem was stiff pivot bearings - if bolt and bearing race type back the nut off 1/2 - 1 turn so arm pivots freely, if 2 ball bearing type remove and bend springy plate slightly so less pressure on bearing balls, clean bearing surfaces and relube with Dexron auto transmission oil.
You will need Torx screwdriver for working on these.
Also clean lens carefully with dry cotton bud - no solvents - may remove optical coating.
Another cheap source maybe is second hand/old Philips/Marantz machines from loppemarket etc. or local repair shops will usually have an old written off machine they might part with.

Hope this helps,
Regards Eric McMillan.
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Old 15th March 2002, 04:13 PM   #3
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Default mechanical problems

Goodday Eric,

how do you recognize stiff bearings? My CD-931 which uses a CDM9/65 started to develop skipping, almost always on tracks 1 and 2, at first only onesome disks and only when it was still cold, i.e. not yet warmed up by the amp it used to sit on, later on practically all disks and also when warm

I found the pivot arm to move freely, at least to my feel. I checked the output of the tracking and focus servos, and the output looked ok, i.e. +/- several 100 mV of offset, depending on where on the disk I was and a low frequency modulation of about also several 100 mV. Hence I concluded there was no mechanical problem. The eye pattern also looked ok to me.

I found the grounding and decoupling to be terrible on the focus and tracking amps. When I redid that, the player worked ok for a couple of months but then everything began once again.

I can get a supposed replacement transport (CDM9/44) for about 100 Euro but that seems to big an investment for an unsure outcome. I have basically written off the player but wouldn't mind a cheap cure.

1) Is there any way to check my diagnosis that there was no mechanical fault?
2) I thought it might be the laser diode loosing power, Elso tends to agree. Do you have any experience in readjusting the laser power?

Greetings,

Eric
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Old 16th March 2002, 03:35 PM   #4
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Default Cdp Repairs

Hello Capslock and all,
Quote:
1) Is there any way to check my diagnosis that there was no mechanical fault?
2) I thought it might be the laser diode loosing power, Elso tends to agree. Do you have any experience in readjusting the laser power?
If you give the swing arm a flick it should bounce off the end stops back and forth nicely a few times - not much stiffer than this and they don't like it.
Spin motors also give problems - low currents cause/allow oxidation of commutator or something - causes slowish enough spin up of disc to cause error - Pioneer cdp suffers this badly/regularly - A cure is, disconnect any connection from the motor to any pcbs, with disc loaded so as to give flywheel, apply 10V or so and spin motor upto a medium speed and quickly swap polarity - the disc will slow and then reverse - do this cycle a dozen times and this should give better motor performance.
Also droplet of Dexron ATF in all bearings including slides and motor shaft.
To adjust laser current, first step is with a fine permanent marker (go and get it now before you start to tweak anything !!!!!!), make sure you mark the laser power trimpot position accurately and tweak it either way in steps of 10 degrees or so - too low and no tracking and too high can cause photo diode preamp overload - carefull tweaking and you can get it. Also hold an ear close and have a close listen to the sound emitted by the lens actuators - 'fine' tune it this way - this can subtely alter the audio output.
The first repair step however is to resolder any joints that you don't like the look of - power supplies, connnectors, surface mount ics, driver stages, anything that runs hot, etc..... be thorough - Philips soldering process sucks bad in my experience........ use good solder...... Multicore Savbit 2% copper solder wets nicely and sounds good to me......
If you can make it work that is great, if you have a bunky laser assembly that's just too bad, but it can be good fun trying - I hope that you have had fun learning by experience and thereby better equipped for the next time.
Experience ? - Several thousand cd playeys of all types during 25 or so years repairing all sorts of makes and types of hi-end and domestic and pro audio stuff - and video and tv and just about anything else that plugs in or runs on batteries etc.............
Also some pretty interesting experimenting too.
If anybody has any such questions please feel free to ask - maybe I can help.

Regards, Eric.
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Old 18th March 2002, 10:05 AM   #5
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Default CDM9

Hi Eric,

thanks for all this useful information. I tried the spinning motor part, will reassemble the transport before I start operating on the pivot arm.

The CDM9 is the tiny unit with the chrome-alloy chassis. The pivot arm with the laser assembly seems to have a default null position at about 1/3 of its possible path from center to edge. This position seems to be defined by some sort of rotational spring mechanism. When I give the arm a kick towards the center, it won't even reach the far-end stop, it will simply bounce off the center stop, travel slightly beyond the null position and then return to it. When I kick it to the far-end stop, it will bounce back, bounce against the center stop and come to rest at the null position.

Is this normal? I still assume that a stiff bearing would produce very high servo output voltages, which I don't see.

By the way, this is the first pick-up on which I haven't seen a pot to adjust the laser power. Maybe I will see it when I disassemble the spring that holds the bearing.

The lubricant that you describe, do you know what it contains? Or is it really automobile transmission oil? I would have tried some WB40, but was not sure about its outgassing properties.


Greetings,

Eric
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Old 18th March 2002, 01:56 PM   #6
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Default Not the ******g WD40

Hello capslock, in the older mechanisms, the laser current/coil current ribbon cable causes the the swing arm to come to rest around 1/3rd way out from center.
It should pivot freely between end stops and come to rest gently.
This ribbon is glued to a chassis plate and can become unstuck, and foul the swing arm preventing the arm going all the way to the center of the disc - no read TOC, no play disc.
The laser power pot is somewhere on servo pcb.
"To adjust laser current, first step is with a fine permanent marker (go and get one now before you start to tweak anything !!!!!!)".
Dexron ATF is indeed automotive automatic transmission oil - years ago somebody told me that it has bronze dissolved into it to prevent bronze/brass thrust plates from erosion.
I have been using it for 15 years on fine mechanicals without grief - sewing machine oil oxidises and turns to gum - even seizing small DC motor bearings.
WD40 is only suitable for undoing seized nuts or for lubing your front gate - the inventors of this **** should be shot.
Also it will creep throughout the whole chassis, getting onto belts and pulleys etc, and also evaporates and recondenses onto other parts including lenses.
DO NOT USE THIS TRASH - you have been told

Hope this can help - let us all know what you find,

Regards, Eric.

PS - Don't ever use belt grip either - yep, I've seen it all !
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Old 18th March 2002, 08:19 PM   #7
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Default car oil and pots

To my name-fellow:

Well, all I have handy for is some super high quality engine oil for my car. My ask my colleague who is a car repair nut for some transmission oil, automatic transmissions are not common here...

The whole Philips CD-931 PCB does not have a single pot, as it was one of the first CD players to use fully digital servo circuits (believe it or not, I just bought a new cheapo Kenwood changer with Sony Chipset that still has three pots for tracking offset and gain and PPL gain).

On more modern Philips players with the CDM-12 transport, the laser power pot is situated on the ribbon cable, along with either a TDA???? or some discrete circuit.

Greetings,

Eric
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Old 19th March 2002, 09:56 AM   #8
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Default more tips & results

The chip that can sit on the ribbon cable is a TDA1302 photo diode amp and laser diode driver.

When you do the spin-the-motor-hard trick, use an old CD-ROM as a flywheel, by all means! The magnetic puck in my CDM9 does not really center all to well, so the rotation is slightly excentric. At the high rmps induced by appling 10 V to the turntable mote, the disk would sometimes hit the tray. This ruined the surface of the disk. Fornutately, I used a CD-ROM that I had made for listening in the car, so I can make another copy.

The ribbon cable seems to be causing the self-centering effect but it is not glued to the chassis, but clamped in a position well-defined by the design of the chassis. I have not yet taken apart the mount/bearing assembly as the TORX key needed is so small it is not in my set. I have, however, loosened the spring a little. See what happens... Having a measureable criterion like "AC voltage on tracking servo output not to exceed 500 mV" would be really helpful, though. Any experience?

On second thought, I don't think it is the laser that causes the skipping. I have one type of CD-ROM raw disk that seems to have such a low reflectivity that many older and some new audio players won't play it. On the Phillips, it caused no more and no less problems than any regular CD. If the laser was dying, the problems would have been more pronounced with this type of CD-ROM...


Eric
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Old 19th March 2002, 01:42 PM   #9
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Hello Eric, (good name!)

" At the high rmps induced by appling 10 V to the turntable mote, the disk would sometimes hit the tray. "

Aaahh, you did not read closely enough - " apply 10V or so and spin motor upto a medium speed and quickly swap polarity - the disc will slow and then reverse " - see !, it says medium speed!

In jap machines, a cause of track 1&2 mistracking is piece of junk on turntable causing the disc to wobble (disc is spinning fastest here) and causing lens to run out of travel, or focus servo to run out of frequency response and/or clipping, also DC offset.
Another cause is buffer under run causing interrupted audio, caused by slowish spin motor (bad commutator contacts).
To tell properly you need a CRO to look at the focus and tracking coil drive signals and the EFM Signal (Eye-Pattern).
This should tell you whats is going on.
I have replaced plenty of jap pickups where the emitted red light looks to be ok, but will not give a good enough efm signal to work.
I understand that the focus and tracking photo diodes can become noisey or something.
There was also a Yamaha pickup with a s/mount PD preamp ic that went faulty.
Sony Kss-240 pickups with preamp and PDs on the same chip can go bad too - a lot !.
Photo diodes seem to be a bit unreliable in other applications too.
I have also recovered some pickups by removing lens assy covers and cleaning internal prism surfaces - this is pretty tricky but.

Maybe this can help.
Regards, Eric von Downunder.
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Old 19th March 2002, 02:07 PM   #10
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Default CRO & junk

What is a CRO? I have looked at the focus and tracking driver outputs with a DSO (digital sampling oscilloscope) and as I said, there is no sign of overdrive, at least amplitude-wise.

The turn-table, or rather the magnetic puck is definitely junk. It has too much play, so it can clamp onto the turn-table knob it different positions. When the CD has been loaded by the tray mechanism, the puck will ususally (but not always) wobble by 1-2 mm. I can use my fingernails to adjust it so it wobbles by only 1/10th of that. Vibration of the metal turntable chassis is substantially reduced. However, there was no correlation whatsover between the positioning of the puck and the skipping problem...


Eric
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