Repair of an MS9710B OPTICAL SPECTRUM ANALYZER

[lowtension]

Hello,

I have a MS9710B with a problem on self test Optical error :008 Grating Error, checked that the grating mirror rotates slowly on startup and stops giving this error.
Where do I have to search for the fault ?  is it an alighnment error or hardware fault ?

Thanks

[t_ryner]

Make sure to check the fittings, screws, ETC on the motor. Any pictures would help. Does it work still after the error is resolved?

[lowtension]

Hello,

I have checked, There are no mechanical problems,  the large grating mirror is driven by a motor and coupled to a Canon KP-1M laser encoder, it seems that it does not lock to the correct postion on the power up sequence , possebly the encoder circuit is not working ,  I will now try to understaand how the encoder works and follow the lines to the board and check.

[lowtension]

Some observations:

1- When unit is off and giving little force by my finger to the grating mirror frame it rotates freely without any resitance .

2 - When the instument powers up, after 2 sec. the grating mirror starts to rotate  slowly in a constant speed and is very stiff for about 1 and a half revolution  and then it stops in a locked/"braked" position giving the grating error code. The machine stays at this state until I switch it off, then the "brake" realeses .

One intersting observation is that during the 2nd step when it starts to rotate for about 1 an a half revolution, if I force my finger on the mirror frame , it goes free from the locked state and the grating errors appears upp directly after that. So I suspect that the motor control is  working   , the encoder detects thatthe mirror is stuck by my finger and realeases the locked rotational state to relaes the mirror free giving the same error.

also, if I unplug the  encoder socket to the controll board and power upp, the mirror will try to rotate on start but in unlocked manner (swings a little and tatty)  but stops directly giving the same error. 
It seems some how the encoder and the motor circuit works (?) but not 100% correct since it can not  ock the mirror in the correct position.

[lowtension]

Is there any other sensor that detects the corroect position of the grating mirror?
Thanks

[brunomp]

Hi, i have the same problem.
Can you help me ?
You repair your machine?

thanks