DM-4800 Output distorted and low level

[cliffb]

On our DM-4800 there have been times when the output has been distorted and at the same time much reduced in level. Usually turning on & off has corrected the problem but now it has reached a point where the output level is practically non-existant. It does not matter which outputs are used (Phones, Stereo Output, Monitor Outputs) the result is still a very faint signal although the meters (meter bridge) are showing a very healthy signal. I have been through the diagnostics and the audio units are showing as being OK and a factory reset has not made any difference.
It looks as though it might need some attention by Tascam but just wondered whether anyone else has experienced similar problems and what the outcome was.
Many Thanks.

 

[cmaffia]

Sounds like the exact problem posted in this thread.
See Fiber's response 3/4 down:

DM-3200 distorted output

 

[bob_w]

I just removed a customer's DM-4800 with the exact same symptom. Not only does it distort and become lower level, it also exhibits a random monitor section of DIM activation of the "to slate" and "to studio" on it's own. Observing any output during the failure on a scope shows tearing of the signal's (sinusoidal) digital composition down to the base line. I suspect a D to A converter or a processor has developed an intermittent connection. Cold solder joints seem to be the only problems that occur in this model. As stated in this thread, the only resolution is to return it to the factory service center. Even the service manual does not include any actual schematics for troubleshooting. Block diagrams, board lay outs, exploded views and tons of info, but no schematics, so in house servicing is not an option.

My dilemma is that my customer discarded their shipping container a year ago. Would any of you have one you could part with?

 

[Will Miho]

Again, the other possibility is the software in the DM4800 like many digital mixers will often crash, particularly when you build presets on top of presets. Before returning a console for repair, back up the presets to computer and try an sram init. This restores factory settings and cleans up the sram.
Often over the time the sram can become corrupted, and every time you do a save based on a corrupted preset the problem in the sram will get worse. This is the first thing they will likely try when you send in the console I think, with the Calrec consoles it was the first thing service techs would do. Finally the service guy after 4 visits in 3 weeks just taught me the procedure, but problems would always return on that puppy until I finally reinstalled the firmware.
Anyway having a "clean preset" that has no routing or anything assigned anywhere that one always builds from is a best practice I think with digital consoles in general, and with the DM4800 in particular which gave me occasional weirdness until I started doing that.

 

[darthfader93]

hey man did you ever get this fixed? im having the same problems, its not really in my budget to send in for repair. ive opened it up and im looking at the master pcb. i dont see anything thats messed up. but i have limited experience with this so there could be something im not seeing

 

[cliffb]

It has been sent in for repair (still under a extended warranty) and will report back when it returns.
Thanks

 

[darthfader93]

alright thanks man. i was thinking about replacing all of the control room monitoring jacks but then i remembered it happens in the control room monitors and in the the headphone monitors at the same time. i highly doubt all of thosewould go bad at the same time. it has to be a damaged ribbon cable. i looked up the master pcb and i cant find the part for sale. im gonna keep trying to find something that looks damaged

can you also give me a total price once its repaired? did you send it to the tascam center in cali or to a local repair?