Help! CONRAD JOHNSON DF1 CDplayer-preamp - diyAudio
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Old 28th January 2010, 02:33 PM   #1
dray177 is offline dray177  France
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Default Help! CONRAD JOHNSON DF1 CDplayer-preamp

It's my second thread now !

I have a scarce DF1 Conrad Johnson CDplayer / Preamp from the begining of the eighties.
And with this issue :
- the CD turntable motor is continuously spining at high speed as soon as power is ON,
- however it is still possible to read CD ( sonically very nice ) when you press "play" button : then all things are OK,
- and it is possible to get next, preview & pause functions without problem,
- but if you press "stop" or "eject" buttons, spining problem on CD disc motor comes back as at the begining.

This DF1 Conrad Johnson is a tweaked common Philips CD350 player with a typical Conrad Johnson treatment for D/A & preamp stages.

I think problem is due to the defective IC 8bits microcontroller : MAB8441P-T042

Have you ideas about that ?
I need your help.
To consider it as an old scrap, grieves me !!

Raymond

my DF1 :
Click the image to open in full size.

and this MAB8441P :
Click the image to open in full size.
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Old 28th January 2010, 03:16 PM   #2
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Quote:
Originally Posted by dray177 View Post
I think problem is due to the defective IC 8bits microcontroller : MAB8441P-T042


Not likely at all.
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Old 28th January 2010, 03:27 PM   #3
dray177 is offline dray177  France
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Originally Posted by analog_sa View Post
Not likely at all.
Please, explain you a bit more...
I am ready to understand.

Raymond
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Old 29th January 2010, 06:04 PM   #4
Mooly is offline Mooly  United Kingdom
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Were there some problems with the servo PCB under the pickup on these... electroylitics ? and poor joints. There was more than one motor type used too I seem to remember, DC motor, hall effect DC brushless etc.

I have an old CD150 and it looks the same as your lol

Edit... Agree with analog sa... it won't be the Micro, guaranteed
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Old 29th January 2010, 06:56 PM   #5
dray177 is offline dray177  France
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Quote:
Originally Posted by Mooly View Post
Were there some problems with the servo PCB under the pickup on these... electroylitics ? and poor joints. There was more than one motor type used too I seem to remember, DC motor, hall effect DC brushless etc.

I have an old CD150 and it looks the same as your lol

Edit... Agree with analog sa... it won't be the Micro, guaranteed
- You are right Mooly ! Philips CD150 looks like near this DF1 !
- Servo PCB under pickup ( CDM4/28 ) is OK and no bad connections exists.

The only problem is ( consider that, it reads disk perfectly ) the CD turntable motor never stop and runs at high speeds when it is'nt in a reading operation.
For this reason, I think there is a problem with program memory chip as this MAB chip, located just behind face-plate : after CD recognition, CD run must be stopped, till play button will press...

In addition excuse my poor English !
Raymond
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Old 30th January 2010, 02:06 PM   #6
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hi, spinning at high speed indicates no clock input, i think? check saa7220.. chip. either could be a bad chip or the solder joints. if you press on the chip and the player works correctly this is normaly dry joints.

jim
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Old 30th January 2010, 02:31 PM   #7
dray177 is offline dray177  France
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Quote:
Originally Posted by jimmytwos View Post
hi, spinning at high speed indicates no clock input, i think? check saa7220.. chip. either could be a bad chip or the solder joints. if you press on the chip and the player works correctly this is normaly dry joints.

jim
Thanks Jiim

With "saa7220.. chip", you have in mind ERCO SAA7020 ?
I changed it before and spinning speed on the CD motor is still in live !

Today my problem is it's impossible to buy these MAB8441P-T042.
Dönberg Electronics in Irelan have many MAB8441 but not this T042 type ( I think it's a specific program edited for this chip ).
If a diyAudio Member know where it is possible to buy it without a $300 minimum order requirement, my gratitude will be acquired for a long long long time

Raymond

Last edited by dray177; 30th January 2010 at 02:47 PM.
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Old 30th January 2010, 03:10 PM   #8
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As part carrier you need an ordinary CD player (from Philips/Marantz e. g.), that uses exact this MAB8441P-T042 as MCU

There are many lists on the web, where to find the Brand, model-No, laser pick up and DAC chip set. But we need also the MPU/MCU types and the PCM-Decoder/Servo controller/RF-amp list for cases as your's above describted.

Unfortunately I cannot discover such lists.
therefore I have start this thread:

Starting cross reference for LSI processors and display drivers of cd player models
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Old 30th January 2010, 03:29 PM   #9
dray177 is offline dray177  France
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Quote:
Originally Posted by tiefbassuebertr View Post
As part carrier you need an ordinary CD player (from Philips/Marantz e. g.), that uses exact this MAB8441P-T042 as MCU
... ...
Andreas,
VERY NICE your website : http://www.tiefbassuebertragung.de/49628.html

Raymond
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Old 30th January 2010, 03:35 PM   #10
Mooly is offline Mooly  United Kingdom
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Have you tried to fault find by looking at "why" the motor is receiving a run command or what is turning the motor on ?
It's "never" the chip usually...
Do you have a circuit ?
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