Help! CONRAD JOHNSON DF1 CDplayer-preamp

dray177 · 28th January 2010, 02:33 PM

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 :

and this MAB8441P :

analog_sa · 28th January 2010, 03:16 PM

Quote:

Originally Posted by dray177

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

Not likely at all.

dray177 · 28th January 2010, 03:27 PM

Quote:

Originally Posted by analog_sa

Not likely at all.

Please, explain you a bit more...
I am ready to understand.

Raymond

Mooly · 29th January 2010, 06:04 PM

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

dray177 · 29th January 2010, 06:56 PM

Quote:

Originally Posted by Mooly

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

jimmytwos · 30th January 2010, 02:06 PM

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

dray177 · 02:47 PM

Quote:

Originally Posted by jimmytwos

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

tiefbassuebertr · 30th January 2010, 03:10 PM

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

dray177 · 30th January 2010, 03:29 PM

Quote:

Originally Posted by tiefbassuebertr

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

Mooly · 30th January 2010, 03:35 PM

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 ?

28th January 2010, 02:33 PM	#1
dray177 diyAudio Member Join Date: Apr 2008	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 : and this MAB8441P :

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Upgrading the Conrad Johnson Premier Fourteen preamp	Tino_diy	Tubes / Valves	10	12th March 2012 02:13 PM
Conrad Johnson ART preamp question.	robmil	Tubes / Valves	24	16th February 2011 02:59 PM
Conrad-Johnson PV6 Preamp	paulcurrie	Tubes / Valves	3	17th April 2004 07:11 PM
Conrad johnson topology	Stefano	Tubes / Valves	14	1st August 2003 04:32 AM
conrad johnson help	efoda	Tubes / Valves	3	24th January 2002 03:23 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

29th January 2010, 06:04 PM	#4
Mooly diyAudio Moderator Join Date: Sep 2007	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

30th January 2010, 02:06 PM	#6
jimmytwos diyAudio Member Join Date: May 2007	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

30th January 2010, 03:10 PM	#8
tiefbassuebertr diyAudio Member Join Date: Jul 2005 Location: D-55629 Schwarzerden	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

30th January 2010, 03:35 PM	#10
Mooly diyAudio Moderator Join Date: Sep 2007	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 ?