anyone have the plans of the emu 1820? I took it to a technician to see if it can be fixed but here where I live there are not many who are dedicated to this type of electronics. This person reviewed it and found nothing wrong, he tells me that we should try changing the A / D converter. and I wonder if there are plans.
what do you think?
I don't have any schematics although I do own one of these but I did repair mine by just replacing the physically largest electrolytic capacitors inside the unit. I don't recall if I replaced just one or 2 or 3 since it was some years ago. The largest electrolytic capacitor is there to filter the external DC voltage that powers the unit. Mine was obviously bulging at the top and I think there may have been a slight amount of leakage of the electrolytic fluid out of the bottom. This is a clear greasy looking fluid not the colored glue you sometimes see place on purpose.
This failure mode is very typical of electrolytic capacitors when they reach the end of their life. And like HDD's it is not IF an electrolytic capacitor will fail it is WHEN. I have found that the ones being used now in many electronic devices including PC power supplies are poor quality ones made in China. I highly suggest replacement with US or Japanese made capacitors.
Your tech does not need a schematic to replace this type of capacitor. Unless it has blown up (which can happen) the capacitance and voltage values will be plainly labeled on the plastic wrapping around the metal "can". The capacitance values are in standard increments and as long as the voltage rating of the replacement cap is equal OR GREATER (this is important) to the rating showed on the old capacitor then electrically it will work just fine.
Also, if I am not mistaken this (largest cap) is a radial capacitor meaning that both of the leads are on one end. One lead will be clearly marked (again on the plastic wrapping) with polarity. Usually the negative lead is marked with a minus symbol. The new capacitor MUST be installed with the same polarity as the old.
And finally, the physical size must be close to the same size as the old. Too wide a diameter and it will be touching the adjacent components - not good. Too tall and it will not allow the unit's cover to be put back on.
This is NOT Rocket Surgery. And any decent tech if you tell him you want the largest electrolytic capacitors replaced and/or any electrolytic capacitors that look to be failing as in bulging or leaking, he/she should be capable of that without the schematic.
If that does not solve your problem then you Will need to find someone that knows what they are doing and/or find a schematic. But seriously, with electronics this old, 9 times out of ten, the problem is either one or more electrolytic capacitors that have failed, a bad solder joint or an issue with a socket that gets a lot of physical wear and tear. And with the latter two, often just refreshing the solder connections will solve these problems. Again, no schematic required.
If you do end up having the A/D replaced be sure to have the tech replace the largest 1 or 2 electrolytic capacitors while he is in there. They are definitely at the end of their life.