How to make correct adjustment of CDM4

Status
Not open for further replies.
Jump to Latest
T

Tubeee

Member
Joined 2003
#1
Hi all pro,

There are two vars(potmeter) combo with CDM-4 laser pickup system (on the pcb beneath the CDM-4), 4K7 and 22K. As I know these VARs are for the adjustment of laserdiode output and focus.

Questions are:

How to make precisely adjustment. Does anyone has related service manual?

If I change a new CDM-4, do I need to re-adjust these var to a correct value? (I think my CDM4/19 is dying)

need your kindly help....
 
#2
What a hardcore diy'er do on a rainy saturday-night:

Having nothing better to do(?), I took the old laser out of my CD-16 (CMD4-d36) and swapped the internals(laser) from a new CDM4.19. :bigeyes:
Only the platter-motor differs (exept the metal...)🙂

And everything works well, playing now...

Arne K
 

Attachments

  • cdm4-x.jpg
    cdm4-x.jpg
    35.7 KB · Views: 4,062
#3
Hello Rudolf Broertjes,

I just search your previous post:
http://www.diyaudio.com/forums/showthread.php?postid=120456#post120456

I think that's what I want to know now:

I have the adjustement procedure for tracking & focus with the two test points (50mV and 400mV).
Click to expand...

Where is these two test points: (or which registors?)
50mV is for tracking (laserdiode output)
400mV is for focus.

Is this done by using amp-volt meter to measure specific registor and check the amp cross it?

thanks
 
#6
There are always 22K and 4,7K pots and all the chips are usually the same.

The model in question is Marantz CD 883 but I have a couple of other ,diffrent machines and with CDM4/19 laser/drive it's always the same.

In fact this Marantz CD 883 is identical inside to the Marantz CD 65MKII ,just the same main board.

I have similar procedure for CDM 2/10.It goes ..."measure acros this resistor near that chip...and so on"

I need similar procedure for CDM 4/19

Bartek
 
#11
sorry, my head is little bit hard....

i have a cdm 4-19 in my cd 10 that have problems to read toc to many years... after two minutes this problems disappears...
i want to check it , but i've not understand where i have to check the tensions...
first point) the schematic tells that i've to adjust 3501 to 50mV, but in the schematic 3501 is a fixed resistor... and where i have to measure this voltage? across the resistor?
Maybe i have to trim the 3520 (4.7k trim) and measure across the 3501? (probably i think this is correct... but i don't want to kill my cdm... 🙂 ).
second point) trimmer 3568 22k, the schematic tells: in combination with 27 400mV... but where? in the test point 3829 (across the capacitor 470n 2561)?
Thanks in advance for any response and very thanks to Rbroer for the piece of schematic...

question for Cobra 2:
.....and swapped the internals(laser) from a new CDM4.19.
Click to expand...
Where have you found a new cdm 4-19 ??? 😉
Do you know where i can find a new laser or some spareparts for my cdm4-19??
Thank you...
bye to all
 
#13
Halo to all.

I finally managed to adjust my cd player (big thanks to Rudolf).

All the resistors and caps values are exactly the same as Rudolf posted in his schematics but the numbers on my PCB were totaly diffrent.
A little instruction is needed becouse the pictures are not 100% clear.
50mV has to be trim with 4,7K pot and measured across 4,7K resistor (points "1" and "2") and 400mV has to be adjusted with 22K pot on point "27" to ground.

I found the 4,7K resistor on my board and "27" point on my board happend to be the pin number 6 of TDA5708.
These two parameter vary from one CD to another and from track to track.I used the newest,best condition CD I had in my collection and adjusted on the beggining of the first track.

Also strange 3029 point/part on the way to "27" on the picture didn't exist on my player at all.Rudolf said It might be some pin or test point,but no such thing on my board.

I just thought some may use my expirences.

All best

Bartek
 
#14
I got mine from "till" ...
Click to expand...

Sob...:bawling: , thanks for response...
anyone know a place to find a laser pickup for a CDM4-DM or something where dismount a compatible laser ??

Thanks for the explications... in next days i'll check my cdm and i'll write the results...and the differencies.. maybe it needs to someone other...
Bye
 
#15
Careful with that axe, Eugene.........

If you are having trouble reading the TOC, you can bring up the laser current.

But............

Be careful. It does not take much of an increase to make a big difference. I believe the spec is 50 mV +/- 5 mV across whatever resistor it is. If raising it close to the limit doesn't help, then raising it more to make it work may burn it out.

But if it is already useless..............then you may not have much to lose.

Jocko
 
#16
But if it is already useless....
Click to expand...
😀 at the moment my cd is use-ful... i have to wait a minute and try to play the cd many times when the cd is cold for having the TOC... after this it seems to work perfectly, no skips or other kind of problems... so i don't want to worsen the situation... it's many years that this cd work in this mode.
When i purchased it, after only a month, my laser say byebye and i had send it for repair in warranty.
When it returned, after not many monts, it was afflicted by this problem, and it's affected at now as well, but it's not less than 8-9 years that this problem exists...
I think that maybe the tecnician hasn't done a good work... so i can check now the voltages... i have also to remove the bad out stage of the 2 tda1547 for a D1-like stage... in the meantime i am searching a new laser for the future... but seems that this ******in' laser costs more than gold... and there is very few pieces in all the world...
Bah...
Thank you Jocko... (are you a fan of the twisted sisters ??? 😀 they remember me when i was young.... 15 years ago...:bawling:)

If someone has a service manual for the cdm4 to share it will be a great thing...

Bye to all
 
Status
Not open for further replies.
Top Bottom