MX2424 won't start

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timprince

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mx2424
We have a Tascam MX2424. The issue started intermittently over the last week or so but is now constant. When I turn the MX on the first 4 vu meters would light up like usual but would stay lit and peaked and the display screen is not showing "mounting volumes" as is usual. The green light in the upper analog circuit board is not lighting up and the machine is not responsive to any commands on the RC 24-24 controller or on the face of the unit. The unit remains in this state while power is on and no progress can be made. Basically "locked up".

I took the top off and have re-seated connections on all ribbons that are visible and power connections.
I have also disconnected all SCSI drives, no help.

Any ideas or advise on the next step or probable cause?


Thank you, Tim
 
Might be corrupted operating system software, next thing you should try is with mx2424 turned off, insert smart card with operating system software, turn on mx2424, see if mx wants to install software, let us know how that goes,
Darren.
 
Hello Darren, thank you for the suggestion.
Unfortunately, the smart card boot got the same "dead" results. I have also tried re-seating the ram PCB and have checked the +5 & +12 DC volts (which look good).
Anybody know of a repairman!
Thank you, Tim
 
A bit out of left field, is there a bent pin on one of the scsi connections? Pins shorting out?

I am also trying to remember where the backup battery is in the MX, I am thinking that you may need to dump the operating system by disconnecting the backup battery to unlock the machine, last resort.

Alan.
 
Thank you, Alan. The battery is on the main PCB, close to the large DC power connector. That is an interesting thought. We had the battery out a couple years ago and lost some user configurations but the software was still in tack. Maybe we have been running on the "shipped software"? I removed the battery, still bad. Good idea on the SCSI pins. There are no drives hooked up and I pulled the SCSI ribbon cable. Header looks good, still no luck.
Thank you, Tim
 
Hi Alan, nope. We took the machine to a repair shop in San Jose, Ca.
Funny to see your email as I was just about to phone the shop and see what's up!
Tim
 
Hello Darren,
No, the repair guy said it was a "bad mother board" and would cost $700 to fix.
So we bought a used MX sans output bds for $450, moved the Analog and ADAT bds from the broken unit to the new and we are done.
That being said, I hope to take out the suspect mother bd and and inspect.
Also, now that the other bds are gone I can try again with tapping on chips, hot and cold air shots, PCBA flex, etc. If that gets me no where I may see if Tascam would check it the board.
 
Hi Tim,
Good that you are up and running again.
Now you have spare parts, the power supply in the mx is its weak point so its handy to have a spare, assuming that wasn't the problem with the broken unit, cheers.
 
I have this exact same issue on one of my machines, that happened last night. DId you work anything out Tim ? I found that reseating the memory sorted this out. Fingers crossed this was the problem ........................
 
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If it's anything like what you can see in the next video, I suspect it may be related (as with many other issues) to the PSU not providing enough current (to the DRAM module, to the HD and DVD-RAM drives or both) at the startup. I believe so because once I disconnected the DVD-RAM drive, freezes like the one shown don't occur that often.




BTW I've seen a MX2424 PSU modded so the power cables to the internal HD are directly soldered to the PSU PCB instead of being connected to the main PCB socket, so it bypasses the molex connector that goes from the PSU to the main PCB. Also, there are some other PSU in which the power cables from the PSU are soldered to the main PCB.

Cheers.


PS: Here is what a failing mx-2424 PSU looks like. After +10 years all electrolytics on the PSU should be replaced, as they are prone to fail (even burst or explode). I've also seen some capacitors with swollen tops on an analog I/O card.
 

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I always suggest removing all drives and devices from the MX and putting them in a seperate SCSI tower with it's own power supply, removes almost all the load on the pwoer supply and all the internal heat from the MX.

Alan
 
You're right Alan. Unless a more reliable than the Skynet Electronic 94V0 Tent 20 and better designed PSU can be installed, decreasing the stress on the PSU by removing the drives should be the procedure to follow.
Cheers.
 
Now there was someone here, who was on the old old Tascam forum site, that modded a laptop power supply to power all the devices inside the MX, hard drive, fan etc, but not the MX itself, this took all the load off the internal power supply. I still favour removing hard drives and any other types of drive completely however.

Hands up who did the power supply mod, I did have pics but can't find them on my computer.

Alan.
 
Hi. I just serviced 2 of these and have more to do. This error the OP has of the 4 VUs solid and blank screen is because of bad RAM. Try another stick of RAM. There are status LEDs on the mainboard near the analog input ribbon cable connector. It starts with a centre red LED, but then should switch to green and amber LEDs and boot up. Good luck.

Also, full cap job, hard wire the power supply harness to the psu board, change the fan. That's about it. Beyond that it is probably a parts machine. Cheers.
 
Just to add to the RAM discussion, the RAM has to be the correct make and model or it does not work. I know It's IBM branded 256mb but I can't find the model number at the moment.

I have tried many other brands and none worked.

However when I turned on the machine with the wrong RAM it started up and told me "No Ram Fitted" or something like that.

Alan
 
That would be real helpful to find the model. I need a stick and I've contacted Tascam and a Tascam dealer, no luck yet.
 
I think these units would be ok if the molex solders on the psu board were thicker at the factory and didn't crack over time. Of the 2 I fixed, the worse the burning of the connector, the worse the solder joints. No burning if the joints aren't cracked.
 
When recapping the converters, make sure you cut those cap leads off nice and short on the lower input board or they will short to the case and the psu will cycle in protect. Don't ask me how I know. There is really no clearance under there. Those boards are also super thick trace and large planes of copper and plated holes- very hard to desolder and solder. You really have to give each joint longer than normal heat with the gun, then suck. I've had to go back with fresh solder to fully clean some of the holes. I have about 10 real hours into one machine - so keep that in mind.
 
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