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Troubleshooting Philips CDM4/24 Laser in BeoCenter 9000

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Menahem Yachad
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Menahem Yachad Posted: Thu, Dec 27 2018 7:23 PM

I have a BC9000 in for restoration. I am now at the calibration stage.

The first problem I had was that the laser adjustment does not rise above about 10mV, for the adjustment to 50mV. This has the Hall motor. 

I have confirmed the Decoder PCB fully OK, in my test machine, using my test machine's CDM4 and Servo Assembly.

Menahem


Menahem Yachad
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I am always very wary of replacing a laser immediately, because there is always the real probability that the Servo PCB is faulty, and a new laser will simply burn in short order.

So, Philips (B&O uses Philips Lasers) Service manual has a procedure to test the Servo PCB laser circuit BEFORE installing a new laser, using 2 resistors, a Green LED and an On/Off switch.

Laser voltage to the Green LED must show about 2.3V, with a momentary brightness when changing switch positions.
I connected the test circuit to the Servo PCB, and was astounded to see 8.3V.
The LED was super bright, I'm sure to the point of burning, so I switched off immediately.
Reviewing the Schematics, my primary suspect was the BC338 NPN 6108, which controls the laser supply.
I replaced it with a BC639, and the LED Test circuit now behaved as I am accustomed to it, showing 2.26V, and brightening momentarily when switching. 
Also the Laser control circuit operates perfectly, as during the switching, the Laser Voltage momentarily rises to 2.6V, which is immediately brought down to 2.26V.
So the Servo PCB Laser circuit is just fine.

Menahem Yachad
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The laser adjustments were still not improving, and I checked that the laser is actually working - the RED light is there, quite clear.

So, I am not yet convinced that the laser is shot.

I examined the Focus lens, and noticed that it is very stiff, and cannot move up and down.

So I disassembled it to clean it.

Now, when I push the lens manually, it now moves freely up and down, but when switching on the machine, the lens does NOT move up or down, as it would search for a focus point on the CD.

The Focus Coil measures 22 Ohms, within the Service Manual spec.

Because the Focus Lens was stuck, I suspect the TCA0372 OpAmp, which controls the Focus circuit, and am now troubleshooting that.


Weebyx
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Weebyx replied on Fri, Dec 28 2018 8:33 AM

I can see on your picture, that you have not used the correct Philips/Vishay C2103 capasitor ?

I actually thought that you might never get a servo PCB functioning perfectly without using this specific C2103 ? The many 35/45/65/7000 cd's I have seen not working, always first came back to life perfectly after using the correct capasitor ?

Is there any reason as to why you are not using the correct one ?

/Weebyx

Menahem Yachad
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I have serviced many of these Servo PCB's, and they all work just fine with Panasonic FC, FM, or Nichicon HE or PW 105°C Low-ESR capacitors.

I'm sure that any other equivalent reliable capacitor would work just fine, as well.

Having scoped that circuit (among many others), the waveform confirms there is absolutely no "magic" in the blue Philips capacitors, and there is NO technical justification to NOT use any other high-quality capacitor instead. 

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Dillen replied on Fri, Dec 28 2018 10:27 AM

Menahem Yachad:

I'm sure that any other equivalent reliable capacitor would work just fine, as well.

My experience from doing hundreds of these drives, is that nothing but a Philips/BC capacitor can be guaranteed to work.
And I have tried A LOT of different capacitors, mainly because I at some point had difficulty finding old stock Philips caps.
I cannot see any difference on the scope either, but there definitely IS a difference in functionality.

It's the only axial capacitor on the board, all others are radial (and not even Philips brands in most machines).
That blue axial was chosen for a reason.

The technical justification lies in the capacitors filtering properties. I have a feeling that the keyword is "ringing", but with no scope images to
show it, I cannot be sure.
Its capacitance is less important. You could even fit a 47uF.
The bad original C2103 capacitors will usually still measure fine as capacitors and carry on wonderfully if tested in other circuits.
It's like their filtering properties "wear out".

At some point I found a cheap chinese brand capacitor type that also seemed to work.
It turned out to only last for about 50-100 playing hours for each replacement. It "wore out" even faster - but still worked fine as a capacitor
in other circuits.

I would also replace C2103 with a blue Philips/BC as the first thing if on my bench.

Martin

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Exactly right Martin. If that blue Philips is not there for a good reason, why use it?

When Anthony Garza originally told me about the problem, many years ago, he insisted that I replaced the c2103 with a Blue Philips. He knew something even then.

Regards Graham

Menahem Yachad
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Gentlemen

I'm glad this subject has been opened.

Firstly, if there is empirical proof that the Blue Philips cap is better, I will be the first in line to start using them again.

However, until now, all I have seen is "He said", and "They said".

That doesn't constitute engineering proof.

 

For the history of WHY Philips used these capacitors, we need to look at the BIGGER picture of the corporate alignment of the European companies in the 1970's and 1980's, which was an extremely turbulent time in the Electronics industry, with the Japanese making destructive inroads into the markets controlled by Philips, Grundig and others.

I worked for Grundig right at that time, so I remember it extremely well, shutting down the productions lines in Germany, and moving them to Portugal.

 

Does anyone ever remember seeing Radial Philips capacitors in any electronic equipment of that era?

Nope.

Why not Philips Radial caps in B&O (B&O was partly owned by Philips for some time)?

Philips made ONLY Axial capacitors, and they made absolutely CERTAIN to use their OWN in-house Components (where possible) on their PCB's. That's why (failing any technically-proficient position) we see that Blue capacitor in Position C2103. 

 

Has anyone ever taken a good look inside other high-quality European equipment (besides B&O), such as Studer?

What's inside are Roederstein Radial caps. You won't find a single Philips capacitor inside. Competition issues, during a VERY tough time.

BTW, B&O used Philips Axial caps, and Roederstein Radial caps.

 

So Philips had to make a purely commercial decision who to use for Radial caps (during a time when money was in VERY tight supply).

I'm sure they looked at Roederstein, but they made the (excellent, in hindsight) decision to go with Nichicon.

 

If any of you have worked on any Studer equipment (as I have), you already know with absolute certainty that every one of the hundreds of installed Roderstein caps is beyond shot. 

And if we look at Philips' CDM PCB's - the same ones used in B&O's players - we see that ALL the Nichicon caps are just fine, while the Blue Philips caps are completely shot.

 

Now, before throwing out more "But He said"s, permit me to ask ONE simple question.

Is there anyone out here, who has done EXACTLY the following test procedure to PROVE, once and for all, that the Blue Philips cap is superior for position C2103?

 

1. Installed a new Blue Philips cap of 33uF or 47uF onto the Philips-manufactured Servo PCB, and had the laser return to normal operation.

THEN

2. Removed the Blue Philips cap, and installed a high-quality 33uF or 47uF Nichicon (Philips' primary outside choice) in the same position, and then witnessed a complete failure to work?

 

If there IS somebody who has that empirical proof, please stand forward.

 

If there is nobody who has that proof, I cannot accept conjecture or "He said", as a pertinent argument.

Engineering is based on pure facts, not conjecture or opinions.

 

At the end of this troubleshooting, I will do EXACTLY that test, and let you all know how it goes.

 

And if I am proved wrong for having used a Nichicon cap INSTEAD of a Philips cap, I will be the first to admit it.

 

Until then, kindly let's stick to facts.

 

Menahem

chartz
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chartz replied on Sat, Dec 29 2018 5:00 PM

Hi,

I use BC axial caps as well. Some retailers still stock them near me so it’s a no-brainer.

I just admit that other, possibly better caps, don’t work well here, with CDM 2/4 transports becoming noisy, erratic, picky.

Whatever the reason is, the BC works every time, so let’s be humble and accept that. 

Well I am and I do!

 

Jacques

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Dillen replied on Sat, Dec 29 2018 6:01 PM

Menahem Yachad:

Is there anyone out here, who has done EXACTLY the following test procedure to PROVE, once and for all, that the Blue Philips cap is superior for position C2103?

 

1. Installed a new Blue Philips cap of 33uF or 47uF onto the Philips-manufactured Servo PCB, and had the laser return to normal operation.

THEN

2. Removed the Blue Philips cap, and installed a high-quality 33uF or 47uF Nichicon (Philips' primary outside choice) in the same position, and then witnessed a complete failure to work?

 

If there IS somebody who has that empirical proof, please stand forward.

Here.

Not sure if that's enough to consider it imperical proof, though, but as mentioned above, the capacitors seem to "wear out", - some sooner, some later.
Most capacitors, even ones of the "popular" and/or "trendy" brands cannot be guaranteed to work. And even if one might seem to work, it won't be for long.
Fit a blue axial Philips/BC (and it could easily be an old stock Philips from the late 1980s, as long as it's unused!) and the drive will play on for
at least the next decade.
That's my experience.
That's the facts as I experience it and that's what I have to share.

Philips did make radial caps in the 1980s.
These - or some just like them - were around back when I built a lot of electronic home constructions in the mid-late 1980s: https://www.tedss.com/2020021545

I find them in Beogram CDX etc. power supply boards, Beocenter 2100/2200/4000 power supplies etc. and I'm sure I have also seen them in some TVs etc. but I have mainly found them in other brands units - even in JVC/Panasonic.
B&O went primarily, it seems, for ROE, Nichicon and (unfortunately, but it keeps us busy) Samwha, though some of the latter seems to age surprisingly well compared to others of the same brand. 

The radial capacitors I see most often used for the CdM servo boards are Nichicon, most often the blue VX-type but I have also seen others.
I like to replace them all while in there, though in most cases replacing C2103 alone makes the drive play.

I don't recall ever seeing a ROE (Roederstein) capacitor on a servo board.
Perhaps that's because, in a CdM 2/4 drive, the only thing made by Philips is the laser block, the mechanicals parts in some drives (I have seen it in jukeboxes) and perhaps some ICs.
It never says Philips anywhere else.

I find the black 1980s/1990s ROE caps many other places (Dolby circuits in Beocord 2000/3300/3500/4500, Beocenter 700x series tape
controller etc. in large numbers) and I like to replace them on sight.

You did A LOT of work on this drive and you generally seem to replace A LOT of components.
There's always a risk of inadvertent human failure involved, and the more work done, the higher risk.
It can never be guaranteed that replacing C2103 brings the drive back in business, but as stated earlier I see it as a point to bring
in order before diagnosing anything else. If it still doesn't play, at least you can rule out this very common issue.

I know they cooperated on many projects, TVs, VCRS and CD-players, but I didn't know that B&O was partly owned by Philips at some point.
When was that?

Martin

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Menahem Yachad:

Gentlemen

 

Is there anyone out here, who has done EXACTLY the following test procedure to PROVE, once and for all, that the Blue Philips cap is superior for position C2103?

 

1. Installed a new Blue Philips cap of 33uF or 47uF onto the Philips-manufactured Servo PCB, and had the laser return to normal operation.

THEN

2. Removed the Blue Philips cap, and installed a high-quality 33uF or 47uF Nichicon (Philips' primary outside choice) in the same position, and then witnessed a complete failure to work?

 

If there IS somebody who has that empirical proof, please stand forward.

 

If there is nobody who has that proof, I cannot accept conjecture or "He said", as a pertinent argument.

Engineering is based on pure facts, not conjecture or opinions.

 

At the end of this troubleshooting, I will do EXACTLY that test, and let you all know how it goes.

 

And if I am proved wrong for having used a Nichicon cap INSTEAD of a Philips cap, I will be the first to admit it.

yes

Until then, kindly let's stick to facts.

 

Menahem

I don't want to argue and I don't have the knowledge or experience to call it empirical rather than anecdotal evidence, but I conducted your test a couple years ago on a faulty BG CD3300. Minimal work done and replaced the known servo cap with a Nichicon. Still didn't work. I didn't spend anymore time with it, ordered some NOS philips axial caps (yes, NOS caps seems like a terrible idea) and when I pulled the Nichicon cap used my PEAK ESR meter and I matched one of the NOS philips to the Nichicon cap I pulled (yes, I know that peak meter isn't perfect for this). Worked immediately. Ran for a few weeks until a new belt arrived, opened it up, stuck the Nichicon cap back in just for fun, ran for 1 CD then wouldn't read. Put in another Nichicon cap, no go. The philips cap back in, worked. Replaced the power supply caps and called it good. A friend has been using it pretty regularly since and has had no issues.
I fall into the DGAF camp about who said what about what and who perceives something as fact or not. I work in medicine and am comfortable with a level of ambiguity and disagreement. I've had luck with the other dozen or so NOS philips caps in other B&O CD players so I just use them.

Menahem Yachad
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Thanks Growler for your experience.

Up until now, every time I've used a Nichicon HE or PW cap in position C2103, I have had no issues whatsoever.

My own machine is with me since new in 1987, and overhauled once about 10 years ago, with all Nichicon caps. Still works perfectly today.

There are many different versions of the Servo PCB's, while AFAIK, there are only TWO versions of the decoder PCB's (at least in B&O machines).

So this Servo may be a version which requires the Philips cap..

I'm open to trying it.

 

Martin,

In the early 1990's, Philips owned 25% of B&O, which saved B&O from shutting its doors.

In 1998, B&O triumphantly bought that 25% share back from Philips, after making a superb financial recovery under Knutsen's leadership.

In 2015, B&O was looking for a new cash injection, but Philips wasn't interested that time around, after B&O sued Philips for predatory pricing practices regarding the sale of TV screens to B&O, between 1996-2006.

 

Regarding that capacitor link, it's actually not a Philips, it's a Sprague. The Series 63 belongs to Sprague (made in the USA).

Sprague, Roederstein and BC-Philips are all daughter companies of Vishay, and production of certain series has been moved to different plants to consolidate.

That means that a 63 of Sprague is now manufactured in the BC-Philips plant in the USA, for example.

Many Roederstein cap series have also been moved to BC-Philips.

I have a business contact who works at Vishay, and he drops me all these bits of useless information, every now and then.

 

Menahem

 

 

 

Menahem Yachad
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Sorry

I just wrote a whole bunch of crap about that capacitor link.

That link was of the Philips 037 series, which was previously made in Europe, and then transferred to production in the USA, and is now discontinued.

So what's for sale, is all obsolete stock. 

If that doesn't bother you, no problem, but if you read the datasheets, shelf-life is quite limited, if there is no current flowing through them (even in a super hot 85°C storage room in Nigeria - LOL).

The relevance of that shelf life to US is that a vintage  machine which has been sitting for 20+ years in an attic, has suffered complete breakdown of all its capacitors.

I prefer to buy only current production capacitors.

BC-Philips still has the 031 85°C and the 138 105°C axial series in production.

Menahem Yachad
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I installed a new CDM4 laser, and it is now working.

I also installed a Philips 47uF 25V Axial capacitor (Series 138, which is the 105°C version of the Standard 031 85°C cap), for the purposes of comparison. That's what I had in stock, so that's what I used.

There IS a performance difference between the 47uF 25V Nichicon HE and the BC 138 47uF 25V, but it's NOT what I expected.

Firstly, they BOTH work, playing many discs, RedBook and RW.

They both give a Cat's-Eye RF amplitude of 1.8Vp-p - see the picture, and Focus Offset of 393mV.

 

BUT!!!!

 

Using the BC138 at C2103:

On a RedBook CD, if I adjust the Laser Strength Poti (supposed to be 50mV) more than about 48mV, the player starts rattling, and shuts down.

I now adjust downwards, and the player is still playing fine at about 15mV, at which point the Cat's Eye is now 1.4Vp-p.

I finally settled for an optimum adjustment of 32mV, and a Cat'sEye of 1.8Vp-p.

 

Using the Nichicon HE at C2103

On a RedBook CD, if I adjust the Laser Strength Poti (supposed to be 50mV) more than about 60mV, the player starts rattling, and shuts down.

I now adjust downwards, and the player is still playing fine at about 25mV, at which point the Cat's Eye is now 1.4Vp-p.

I finally settled for an optimum adjustment of 46mV, and a Cat'sEye of 1.8Vp-p.

 

I then reinstalled the Philips cap, and that's how it is now.

The machine is still open, while I think about this.

 

So, if I appeared to be a  pain, insisting on technical proof, I apologize, and I am very pleased to now have absolute proof of the differences.

 

However, if Philips requires the Laser Strength to be 50mV, and that's achievable only with the Nichicon HE, then where does the Philips cap leave us running at such a low 32mV voltage - Is the current too high in this case? P = V x I.

 

Comments are invited!

 

Menahem


Peter
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Peter replied on Mon, Dec 31 2018 1:58 PM

Menahem,

that topic became very interesting thanks to your knowledge and experience.

Please forgive me a supid question: where the Laser Strength Poti is located ?

Dillen
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Dillen replied on Mon, Dec 31 2018 2:31 PM

The most unfortunate issues are;

1. The circuit design around the trimmer for the laser current adjustment has a FAR to large span.
It easily allows for current settings more than high enough to kill any laser. And even a
very brief setting of a to high current will turn the laser black forever.

2. Some manuals give a wrong testpoint for measuring the current (measured as a low voltage somewhere else).
There seems to be more than one wrong testpoint given in different manuals, and at least one of these testpoints will
never reach the specified voltage, no matter how high you attempt to set the trimmer. Simply because the
stated testpoint isn't related to the laser current at all.

As I'm sure you can see, these two issues combined burned a lot of lasers, because DIY-owners and
tech guys unaware of the manual typos, in desperation, turned the laser current far to high.

My general advice is NOT to touch the setting of the trimmers at all.
If you replace the capacitors, and make sure to fit a blue axial Philips/BC type for C2103, there will be no need for adjusting.

The laser current adjustment is found on the servo board together with another adjustment (usually focus offset).
Changing their settings won't "upgrade" or improve anything. It won't read faster or play better and it won't make a dead laser work or
compensate for bad capacitors. It will only make things more difficult to get back right (and potentially do permanent damage to the laser).

Replace the capacitors - use the correct blue type for C2103, and leave everything else well alone.

Martin

Menahem Yachad
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Peter

Thank you.

That's NOT a stupid question at all. This can get quite confusing, if not familiar with these equipments.

If you look at the VERY FIRST PICTURE in this thread, you will see the SERVO PCB. That SERVO PCB is mounted directly UNDERNEATH the CDM2-4 laser.

 

On that SERVO PCB are TWO White Potis - those are the replacements made by Piher, Model PTC10.

The Poti on the LEFT is the Laser Strength Poti 4K7Ω, labeled 3106 - normally set to 50mV, according to the Service Manual Procedure.

The Poti on the RIGHT is the Focus Offset Poti 22KΩ, labeled 3146 - normally set to 400mV, according to the Service Manual Procedure.

 

There are also OLDER SERVO PCB's, which have ONLY ONE Poti.

That is the Laser Strength Poti, and it is 1KΩ. There is NO Focus Offset Poti on those.

 

To the LEFT of the Poti 3106, you will see the capacitor 2103, which was the subject of this entire discussion.

 

I'd still like feedback and opinions from the other gurus, about my findings on this test.

I've had it running with the Philips Axial cap at 32mV for over 12 hours now, superb musical fidelity, and no signs of any skips or any other types of failures.

 

Menahem

Menahem Yachad
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Dillen:

2. Some manuals give a wrong testpoint for measuring the current (measured as a low voltage somewhere else).

There seems to be more than one wrong testpoint given in different manuals, and at least one of these testpoints will
never reach the specified voltage, no matter how high you attempt to set the trimmer. Simply because the
stated testpoint isn't related to the laser current at all.

Martin

 

Thank you for that.

That is VERY valuable information.

 

AFAIK, the Laser Strength measurement is across R3102, a 472 SMD resistor, same circuit position on Pin 28 of the IC 6101 TDA5708, no matter which SERVO PCB version.

Is that correct or not?

To tell the truth, that is the position I remember by rote memory, since starting to service these Philips-based machines about in 2003, and I've never checked any other manual, if it says differently.

So either ALL the machines I've ever serviced should be defective, or they should ALL be just fine.

I certainly am required to recalibrate the potis, for the simple reason that on a complete restoration, the original unstable carbon potis are junked, and I replace them with Piher Cermet units, far more reliable and precise than the originals.

I never shy away from doing any calibrations on any equipment which I service. I have the equipment and the experience to do the right job, first time, and that is my ethic, even if I am insistent sometimes ;-).

joeyboygolf
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AFAIR the wrong test point was quoted for the offset adjustment.

"AFAIK, the measurement is across R3102, a 472 SMD resistor, same circuit position on Pin 28 of the IC 6101 TDA5708, no matter which SERVO PCB version". I agree with this statement.

Regards Graham

Menahem Yachad
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Thanks Graham

So what IS the CORRECT testpoint for the Focus Offset?

Menahem Yachad
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I have gone through ALL my CDM2 and CDM4 manuals (about 20 of them - B&O, Philips, Grundig, Marantz, Toshiba), and I cannot find any discrepancy about the Focus Offset Measuring point.

They ALL state to measure for 400mV across Component 2136 (470nF film capacitor), which is actually measuring from Testpoint 27, TDA5708 Pin 6 (FElag) to Ground.

That's how I've ALWAYS done that measurement.

So are they all wrong, or is that the correct Testpoint?

Menahem Yachad
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I've found something here.

Follow me carefully on this:

 

Reviewing the Technics SL-PG340A Manual, which has the CDM4, and uses the TDA8808 (instead of the TDA5708), see attached pics of B&O Servo PCB and the Technics Servo PCB.

The TDA8808 is functionally identical to the TDA5708, except that it is a lower voltage version.

 

Both circuits are identical, but pay attention:

The blue component is a 120KΩ resistor, and that's the component which Technics states to measure across for 400mV.

The orange component is a 47nF capacitor, and that's the component which Philips states to measure across for 400mV.

 

So who's right?

Technics or Philips?

Philips could have very easily made a typo, by specifying 2136 instead of 3137.

 

I'm going to do the test on this machine right now, and see what happens.


Menahem Yachad
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Technics Service Manual for Focus Offset Adjust - Measure across the BLUE Resistor

Philips Service Manual for Focus Offset Adjust - Measure across the ORANGE Capacitor

 

 


Menahem Yachad
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For comparison now, see the Philips Service manual extract:

Technics Service Manual for Focus Offset Adjust - Measure across the BLUE Resistor

Philips Service Manual for Focus Offset Adjust - Measure across the ORANGE Capacitor


Menahem Yachad
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OK, Done.

Nice exercise, but that confirmed that the Technics manual is identical to the Philips manual.

 

Examining the Actual Technics PCB, the Testpoint is ACTUALLY the JUNCTION between the 120KΩ resistor and the 47nF capacitor, then to Ground.

It's NOT across the 120KΩ resistor, as I had previously interpreted.

 

Therefore the Technics Testpoint is the same as the Philips Testpoint.

So, that would confirm that ALL my Philips manuals are correct.

 

Just for reference, I'd still like to see the Manual with the Wrong Testpoints, if any of you have that available.

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Dillen replied on Tue, Jan 1 2019 12:40 PM

I like to give safe advice.
What I do in my repairshop is not always what I recommend DIY'ers to do at their kitchentable.
Messing with the trimmer settings can, as mentioned above, do a lot of harm and I would never
recommend anyone doing this, unless they know exactly what they are doing and have
the necessary instruments, tools, test-CDs etc.

Adjusting is rarely needed, anyways.
And should it be needed, I would recommend owners to let a skilled tech guy take over.

Martin

Menahem Yachad
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Martin,

Of course, that is the safe way.

But here on the Workbench, it's the first place I turn to when I have a query, because I know that there are other men here on a highly-experienced technician's standard who can understand where I'm going, and probably have been there before.

It's also the place where DIYer's can actually learn from solid hands-on experience, not just theory in a book.

I know of some DIYer's here who have been encouraged to invest in proper equipment, and made the advancement to not being scared any longer of doing the correct work. That is the best gift that the Workbench can give members.

This exercise was super experience, putting to rest some doubts which I had, regarding these capacitors, and understanding the differences and technical limitations between them. 

And without my equipment and experience, and good feedback here, I would not have been able to go there.

So thanks to all who participated, including all those who just followed on..

Menahem

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If DIY-ers persists on replacing the (oxidized )trimmers as they expect that they drift depending on heat, they also can measure the values of the old trimmer. Measure the old removed trimmer with it's setting and transfer this onto the new one. Sometimes it needs some calculating when the new trimmer hasn't the exact same value as the old one. It should be a safe starting point. It sometimes helps where you don't know how much effect it has when you turn the pot to the left or right side as it could make a huge difference.

For idle currents it is mostly safe to set the trimmers to 0 ohm. But for that you need to know how the traces are located on the PCB.

BTW, I have a service manual where the measurement has been (handwritten) corrected. I have to look that one up. For me, it also often is enough the replace the old capacitors with new ones. I  measure the old cap C2103 first for it's value/ESR. Then I know when it's way out of it's spec it should make a difference when putting a new one on the PCB.

joeyboygolf
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I can't remember and I have disposed of all my manuals!

Menahem Yachad:

Thanks Graham

So what IS the CORRECT testpoint for the Focus Offset?

 

Regards Graham

Die_Bogener
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The adjust is done in "Test Mode Number 3".

Open and Play will move the swing arm, the disc rotates and the drive trys to read data, the laser is on and you hear music. If it stops, the laser could not read data. Either the laser itself has problems or the rotation speed. In this mode the focus offset is adjustet to 400mV measured across 30C2136 (there is a mistake in the service manual, they are talking about 30R2136, that's wrong...) or very easy: IC6101 Pin6 to chassis ground.Adjusted with trimmer 30R3146

The adjustment during this service mode for the laser current is 40mV for a CD5500 (if a CDM4 drive is installed, CDM2 is completely different...), 50mV for the CD6500/7000, the trimmer 30R3106 is used and measured is across 30R3102 or easy 5V Pin28 of IC6101 to the wire bridge next to the foil connector.

The boards for a 2-pin motor and a 4-pin motor are different... The poti for the lasercurrent R3106 is stated 1K in the old manuals, but 4,7K on the newer versions... and there are further undocumented changes.

 So the laser current ist adjusted for the 4-pin motor (usually CD5500) to 40mV and for the 2-pin motor to 50mV (CD6500+7000)

The blue philips works great, just replace it and it will work. Why? I dont know, but it behaves different to every actual "low ESR" type, the adjustment of the laser current will be different.

I think, the lower the laser current, the better the test quality of the system. and usually you will measure the lower currents with the blue Philips..

 

Martin 

 

 

Menahem Yachad
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Jerusalem, Israel
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Martin,

Haven't heard from you for a LONG time!

Thanks for that excellent info, regarding the 40mV for CDM4 and 50mV for CDM2, if I understood you correctly.

Just to confirm, are you referring to the Hall Sensor motor in Both cases of the 2-pin and 4-pin?

Menahem

 

Die_Bogener
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Yes, 2-pin and 4-pin means the motor for the CD drive. I found different values for this adjustment and thought, that the laser itself could be different between a CD5500 and a CD7000.

But that is wrong, the laser is the same, but the boards are different depending on the motor and have different electronic smd parts. Because of that, the values of the laser are different, because of different resistors sensing the current.

My health is not good, i'm doing just little B&O ... but still here Smile 

Menahem Yachad
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Jerusalem, Israel
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Martin

I wish you good health.

You always offer us excellent tips on good maintenance, and your opinion is always valued highly! 

chartz
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Burgundy, France
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chartz replied on Tue, Feb 12 2019 5:47 PM
Hi,

Just got a QUAD CD 66 for the princely sum of 40 €.

Not working, of course. The seller said, “Bad laser”. Mmm. I’ll take it anyway Sir. Absolutely mint in original box.

The usual 47uF Philips blue of course. Tried something else, pah, useless. Now a Vishay, 47uF 40 V is in place and hey presto everything working fine.

CDM4/16

Jacques

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