Non repairable Mitsubishi DA-A10

If you don't hear any relay working , this just mean that you probably get some DC OFFSET who can be measured between commun point made by R239/R240 and ground
See how much voltage you get there and come back to us

Are all the fuses good (fuses under sleeves) ?
 
I live in Sylvania GA, an hour north west of Savannah. I checked both sides of the fuses and they are all 59.4 to 60.3 volts. If I can figure it out I'll check out the offset tomorrow R229/240. Thank y'all for taking the time.
 
Neat tool that (Bungard Favorit) to replace the thru hole in the PCB. Have used wire and lead length to replace broken/lifted tracks. Cheap PCB material.
 
I noticed that the insulating sleeve on the upper left fuse on your MA-22AU PCB has slid to one side. The left end of the fuse is exposed and may possibly be touching something underneath it. Seems unlikely but a simple fix is a good one, fast and cheap. Check that before you do anything else.
 
It looks like resistor R114 got extremely hot, so hot that it melted the cover off of cap C107 and blackened the PCB board underneath the resistor. The opposite side resistor R214 exhibits no signs on the PCB of this overheating.
 
Thank y'all for the replies, I have to go back to work till the 29th and will finally get the Mitsu cleaned up and resume the process.
 
got to chime in as i got a dead DA-A10 as well, powered on but no relay click, opened up the bottom plate and did a cleaning of the PCB firstly as too much flux residues.
good thing all the fuses for both +/- line voltage going to the power amp all good, just a quick short test.
will power up today and do voltage measurement to see if all fuses are intact...if all line voltage good but no relay click..will focus on the protection circuit.
 
Please don't leave us hanging and let us know your progress.
It’s funny when a thread you totally forgot about pops up. As it happened I got the amp and was excited about getting it sorted out, I steadily lost interest as it became apparent the cost of repair out weighed the value or interest for that matter. I ended up giving it to a tech that was working on some other equipment for me.
We all obviously love this hobby but it’s getting exponentially harder to find good techs. You see post about the younger generations not getting into audio gear, not being able to get anything repaired in a timely manner will not help. When you find a good tech, they are out there, the waiting list can be a year or more, this is no fault of the tech. This on top of parts occasionally not being available fuels the issue.
Finding a tech to repair or restore tube gear or higher end solid state is not that hard if you can get the stuff to them. It’s finding someone that can diagnose and repair an SX750 or Sansui 2000a that has relatively low value but definitely worth saving that is difficult. The good techs are getting older, haven’t met one in his 30’s, in 10-15 years it’s gonna be a lost art.
 
I got some bad news from the tech...He said my DA-A10 had some bad repairs done in the past some of the traces are lifted and its unrepairable.

Can't see why it wouldn't be repairable, I can't see anything so terrible going on in those photos that it would make a piece of gear like that a boat anchor. That's a really nice amp, take it to a different tech if you aren't confident about doing the fix your self.
Good luck, cheers.
 
I ended up giving the amp away years ago. I’m bummed I did, I think I would give it a crack now. I appreciate the comments.
 
General thought: A lot of older audio PCBs are, by modern standards, pretty simple: only one layer, big through hole components, sometimes even a corresponding diagram silkscreened on the back.

I wonder if it would be feasible to desolder a damaged/dead PCB, scan it at high resolution, clean the image up,, and convert it to the files used to drill a new PCB? Feels like that would be a way to solve any number of "burnt trace/lifted trace/gouged PCB" style problems.

https://hackaday.com/2019/12/31/reverse-engineer-pcbs-with-sprintlayout/ seems to be a similar discussion from the retro-computing space.
 
i've sorted out my A10, one of negative output transistor was shorted but had impacted the input drivers as well.
and waiting for the 2 input darlington transistor.
 
Some burnt wires, and an unfinished design (generally it's better to eliminate point to point wires across the bottom of a circuit board), but all it would take is time.

After all, I snapped a chunk off the board in my KA-80, glued it back on, soldered one a pile of jumpers, and it works. Wouldn't have broken a customers board (I was going stupid with it) and I will be making some replacement traces from copper foil tape -- after all, there are commercial products for repairing lifted traces and cracked boards!

I'd hate to pay someone to do that though.....
 
got my A10 singing, one transistor output is shorted on the right channel and few noisy input drivers that's causing the protection to activate.
 
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