Repair R&S CMU-200 FMR5 mainboard.

[John_p]

Hi,

I have a R&S CMU-200 with a FMR5 front module which has a problem. When I turn it on I hear a startup bleeb from the Front module mainboard. Then the Display turns white and system seems to freez.  On an occasion I get an Energy Star logo at the right top corner of the display, but within a fraction of a second the screen turns white and freezes.

Addition :  a VGA monitor connected to the External Monitor output says "No Input signal"  (monitor checked  and Oke on my other CMU)

PCB :  FMR5P 9638.63/4  Rev 4.

Processor K6-2  300MHz  1.8V Core

The HDD is Okay, and the CMU works with my other (FMR6) module.

The Mainboard has quite a few SMD Electrolytic capacitors could it happen they went south ? (Due to age.. 20+ years old)  All those capacitors looks like to be in the power supply of the mainboard.  6x 1000uF 6V and 10x 330uF 6V

Anyone having experience in repairing these FMR5 Mainboards, any hints and tips are very much appreciated.

Thanks in advance, John

[Qw3rtzuiop]

Hello,
i have a picture of an FMR5 plus.

I marked the 3 voltage regulators you can check. Also check the red marked oscillators and the cmos battery.

You can also try and change ram or cpu. These old types are cheaply available on ebay and on flea markets.

[John_p]

Hi,

Thanks for the information. Very much appreciated  ! For now I assume the CPU is okay (and the clock as well) as the Enery Star logo apears occasionaly.  Will fix some wires to measure the voltages of the 3 supply voltages on the board. 

The 3 inductors are one side connected to a Diode and the other side to the output filter cap I assume.. At least this is how a SMPS normally works 

I don't have a AMD K6-2 300 processor laying around only some old Semprons so I can't swapp the processor (right now) 
RAM is working okay in my other board.

Addition :

Replacing the 3.6V Cemos battery was the first thing I did.. Had a few on stock..

Just checked the voltages,

3.31 V ,
1.84 V and
3.32 V

So seems to be in spec. 

Think the VGA (S3 chip) is the next suspect to check. as every now and then I get the Energy Star logo on the display, in most cases only white screen so there is no VGA signal..  This chip gonna be more difficult as it is a BGA package..

[Qw3rtzuiop]

Did you already connect an external display via the VGA output on the back of the unit? That way you can ensure that it isn't a faulty lcd.

[John_p]

Hi,

Indeed I did but I forgot to mention it. The VGA output on the rear gives no picture. I get "No input signal" on my monitor, I've tested the monitor on my other CMU-200 and that works, so monitor is fine and only has VGA input.

So next is checking the Clock frequencies / oscillators. Will put a scope on the output and see if they are there.

[Bicurico]

Don't forget to test the memory SDIMM's.

[John_p]

Don't forget to test the memory SDIMM's.

This was a very good advise !!  My FMR6 was bleeping like an idiot.. No display at all.. This turned out to be a broken SO-DIMM, broken display was a defective inverter board so instead of my FMR5 I now have the FMR6 up and running. Will continue with the FMR5 to get that one back working as well.. To be continued

[John_p]

Today I've tested some old computer SDIMM's 256 and 512MB they all are okay so I have some spares..  One remarkable thing, the 512MB are seen as 256MB.