Changing MDM-7A drives with different Laser-Units (KMS-260B vs. KMS-260E)

[bluemoon]

I am so pleased that there is a forum for the worldwide minidisc community (I'm from germany)

to get still support for these great Sony machines. I have a MDS-JE770 and 780.

my older 770 has inside as you all know the BD-board MDM-7A. This board has 2 possibilities for the

laser unit: KMS-260B or 260E. These 2 different laser-units are working with different settings/adjustments

for voltage and so on.

Question: If I have an MDM-7A with a builtin KMS-260E: Will a MDM-7A exchange with a builtin KMS-260B

work fine instantly "like a plug and play change" or are there settings / adjustments for the laser still to be done ?

I think the answers will apply to the mdm-7S1A BD-boards as well (with 260B and E series)

 

 

[kgallen]

The laser parameters are stored in the EEPROM on the BD (drive) unit. 
 

If the replacement MDM unit is correctly calibrated and is exactly the same type as the original then I would expect the new one to just work. 

[bluemoon]

I was recently able to purchase a new laser duo 260B and 260E 
and yesterday I set out to replace the laser on my faulty MDM-7A.
After disassembly you could see a 260E sticker on the underside. 
I was now able to replace the weak one with a new one and after installing it in JE770
everything worked fine. Just plug and play. I am so happy because there are now
several ways for me to save a defective mds machine. Thank you for your expertise.

[kgallen]

Was the Iop figure for the new 260E similar to the old one? This is 3 digits on the label for example ‘546’. It will range from about 520 to 600.

 

If there is significant difference (say a difference of 2 or more on the middle digit) then you really need to calibrate the machine to the laser. 
 

If the number on the new laser is lower than the old then you will be over-driving the new laser which will shorten its life especially in record. If the new number is higher you might have play, or more likely record, reliability issues. 
 

Good luck and well done regardless!

[bluemoon]

 

Thank you very much for this valuable information. 
I really enjoy learning. Unfortunately I have no way of calibrating it 
and finding someone in Germany is extremely difficult. 
What a shame I thought it would be plug'n play if type b or e was swapped for the same. 
can you tell me what the abbreviation lob stands for? 
On the back there were 2 lines on the old 260e laser: 04411 and C0513.
I assume the 513 is the lob. Unfortunately there was a sticker on the new laser
so that only this information was visible on the new 260e laser: 06311 and 605** 
in the end that means to me that there is at most a 60 to 40 chance 
of having a laser change without a new calibration (for long-term satisfaction). 
Without the possibility of calibration, I would need tons of used MDM-7 and tons of new 
260b and 260e lasers from different manufacturers or suppliers with the chance of different lob values. 
Somebody will fit... or is there an auto-calibration in the MDS-JE service menu? 
My only tools so far have been antistatic gloves, laser safety glasses 
(in addition to working without electricity), some videos and service manuals.

[kgallen]

Forgive me, typing on phone. 
 

My interpretation of your numbers from the labels:

 

Old laser Iop=51.3mA

New laser Iop=60.5mA

 

Iop is optical pick-up drive current. It indicates how much current the drive circuit has to push through the laser to get a defined light output. 

 

From those numbers I would conclude your machine is under-driving the new laser. This is good for laser life but you might find play or more-so record operations are not reliable. 

But… if your machine is working just fine, then just stay as you are and enjoy it!!!!

 

To calibrate you need at least a laser power meter and ideally a small connector jig that plugs into the MDM to measure the Iop current as it’s adjusted. Within the Service Menu there is a process to go through to configure the drive current for a range of power output states of the laser. This isn’t automatic as you need the laser power meter to measure the actual laser output at 780nm wavelength. 
 

I’m very pleased to hear you took anti static precautions. The lasers are very easily damaged especially once the solder bridge has been removed. So well done!

 

Note: 260e lasers have to be driven harder than the older 260b. But since you did a swap from 260e to 260e that is not an issue here.

 

See: https://www.minidisc.wiki/_media/resources/kms260e_lpm_spec.pdf

[bluemoon]

Unfortunately, it is like this:
iop old laser: 5.13ma
iop new laser: 5:XXmA XX=missing numbers

I have now read the service manual again but found some unclear information: 
you can call up 2 iop values in the service menu: you can save a new iop in the device 
and you can read out the labeled one from the pick-up. Would that mean that the sticker
is not necessarily important because you can read the iop of the new laser or is it just that
an iop value that was saved hard at the factory-process by Sony ?

[kgallen]

That read value is so you can store the label value (there is an ‘Iop Write’ menu item) - it’s not part of the calibration that controls the current the machine drives.  But ideally you’d update it if you replace the laser. 
 

The machine probably also has an ‘Iop Compare’ in the Check menu. This can be used to track drift and laser aging based on this stored Iop value. It will give you a percentage deviation and an OK or NG (no good) result. 
 

The text in the Service Manuals does take some getting used to plus working with a machine whilst reading to get the hang of what it’s trying to say. Understanding the auto calibration steps in the SM for portable devices is an art in itself! 😆

There can be up to 4 laser power settings to check - although I think you’re right, you set calibration for two (probably 0.9mW read and 7.0mW write).

 

Your machine works. Take the credit, stop worrying, and enjoy it!