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Replacement of Philips SAA7824HL
Replacement of Philips SAA7824HL
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Old 8th April 2019, 06:17 AM   #1
Kait is offline Kait  Estonia
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Default Replacement of Philips SAA7824HL

Hello to all,
I have a consonance 120 cd player that won't read any cd.
After some investigations and measurements I've come to thinking that it might be philips saa7824HL causing the problem.
So I would like to get some information, is saa7824hl a simple replacement or does it need some kind of programming or configuration to get it working?
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Old 8th April 2019, 06:37 AM   #2
Mooly is offline Mooly  United Kingdom
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Replacement of Philips SAA7824HL
The chip would be a direct swap although any normal adjustments (if there were any) in the player would still need to be performed.

Chips like these are usually the last suspect when fault-finding… that doesn't mean its not faulty, just the least likely.
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Old 8th April 2019, 07:57 AM   #3
Kait is offline Kait  Estonia
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Thank you Mooly.

I know it's very unlikely fot this chip to fail, but I have run out of ideas...

The problem is that after inserting the cd, there is no spinning, no focusing movement of the lens and no laser light.
The only thing it does, is moving the laser head for about 2-3 seconds towards the end of the cd (further away from start switch).

The servo borad includes saa7824hl, mm1469 and ba6208 that controls the tray motor. Unfortunately the original service manual that Consonance has sent me doesn't include any information of the cd servo board.

I have measured voltages on all the supply lines of saa7824lh & mm1469 with DMM and they seem to be within tolerances(according to datasheets).
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Old 8th April 2019, 08:09 AM   #4
Mooly is offline Mooly  United Kingdom
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Replacement of Philips SAA7824HL
If the lens isn't performing a focus search routine then I suppose its possible it could be the IC but I would still check other things first.

Make sure that all the inputs to the system control are correct, such as things as any tray switches etc.

Its also always worth going around every pin on the chip with a scope and seeing that what is expected is actually present. Using a scope rather than a DVM for measuring DC voltages can sometimes be more revealing.
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Old 8th April 2019, 08:42 AM   #5
Kait is offline Kait  Estonia
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Quote:
Originally Posted by Mooly View Post
If the lens isn't performing a focus search routine then I suppose its possible it could be the IC but I would still check other things first.

Make sure that all the inputs to the system control are correct, such as things as any tray switches etc.

Its also always worth going around every pin on the chip with a scope and seeing that what is expected is actually present. Using a scope rather than a DVM for measuring DC voltages can sometimes be more revealing.
Well, I know, the scope would be appropriate for this kind of job but at the moment i'll have to get by without it.
A few photos of the servo board:

Click the image to open in full size.
Click the image to open in full size.
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Old 8th April 2019, 09:01 AM   #6
Mooly is offline Mooly  United Kingdom
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Replacement of Philips SAA7824HL
I've no quick answers I'm afraid. The first thing to look at is why the lens doesn't do a focus search routine. That involves checking the system control really does recognise that the drawer is shut and that the logic inputs to tell it so are correct.

If that is OK then look at the focus output signal from the chip that will go on to drive the focus coil drive amplifier. Although the laser should also be lit at this point, looking for laser light isn't always conclusive simply because it can be hard to see.

In other words concentrate on the focus search not happening and not the laser not lighting.
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Old 8th April 2019, 09:22 AM   #7
Kait is offline Kait  Estonia
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There is no voltage output at pin 80(laser output) of saa7824
The the drawer acts as it should. Open and closed positions are recognisedsed at least display is showing them correctly.
As far I understand, there is some kind of "start disc reading" input present at SAA chip, because it's sending out sledge motor command for MM controller.
I'll try to replace the SAA chip and hopefully it will work..
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Old 8th April 2019, 10:10 AM   #8
Kait is offline Kait  Estonia
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Quote:
Originally Posted by Mooly View Post
In other words concentrate on the focus search not happening and not the laser not lighting.
Thanks for information and I'll take another look at this circuit.
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Old 8th April 2019, 11:42 AM   #9
Mooly is offline Mooly  United Kingdom
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Replacement of Philips SAA7824HL
OK

If you are sure the SAA is receiving all the right info then I guess you have to change it to be certain.
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Old 12th April 2019, 06:06 AM   #10
Kait is offline Kait  Estonia
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I've replaced saa7824hl with saa7826hl which I found on some board lying around and got it working. Does anybody know the differences between 7824 and 7826?
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