• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Yamaha MX-A5000 service issues

Find IC21 and IC31 these are thermal sensors on the same heatsink as the output transistors. They are the heat sensors for the fans I believe. Try directing external heat directly on them . If possible. They are a 3 pin device in a TO-92 package.( LM61C1Z )
 
Last edited:
avionic said:
Find IC21 and IC31 these are thermal sensors on the same heatsink as the output transistors. They are the heat sensors for the fans I believe. Try directing external heat directly on them . If possible. They are a 3 pin device in a TO-92 package.( LM61C1Z )
Click to expand...

That is where I was at with the hairdryer.
 
avionic said:
Are they 24vdc fans?
Click to expand...

According to the drawing they show 24v and 1v.

I thought I got the IC's hot but maybe not enough, I will try again tomorrow.

I will also remeasure the W251 +5v Stby, MG and THM 0.85 to 1.0. I not sure what MG is.
 
Yamaha5000 said:
According to the drawing they show 24v and 1v.

I thought I got the IC's hot but maybe not enough, I will try again tomorrow.

I will also remeasure the W251 +5v Stby, MG and THM 0.85 to 1.0. I not sure what MG is.
Click to expand...

W251:
+ 5v STBY = +5V measured
MG is ground
THM is defined in the service manual as AD, not sure if I understand the AD designation
I also read where FAN_CTRL is a PWD, not sure if I understand PWD

After putting a great deal of heat to AMP Power 4 & 5 the fans do operate. I did find that the screens on the fans had pushed in against the fans and thus creating friction and would not allow them to turn or very limited.
 
The sensors tells the CPU to enable the fans at a predetermined set point. Good chance you have a CPU issue with no new spare parts available per the schematic. I just don't see either scenario of both sensors being bad or both fans being bad.
 
avionic said:
The sensors tells the CPU to enable the fans at a predetermined set point. Good chance you have a CPU issue with no new spare parts available per the schematic. I just don't see either scenario of both sensors being bad or both fans being bad.
Click to expand...

I hope that is not the case! I need a temp probe to see at what temp the CPU activates the fans. The heat sinks are so massive and absorb a great deal of heat. I did notice the point of turning the fans on until the amp just shut down was a very narrow window.
 
Yamaha5000 said:
I am happy to post that I followed the instruction to reset the CPU, now I have full sound. One item still an issue is the cooling fans are not running. Therefore that error code in memory of THM/OLV protection detected excessive heat in the output.
Click to expand...

Curious, I have the same unit and the pre amp is suddenly doing the same, blinks a few times at start up then nothing. I'm about to trouble shoot per the OM, wondering if there was an actual process you used to reset the CPU or just unplug? Thanks!
 
Yes there is a procedure that is outlined in the service manual. I had to read it several times to understand, once over that it was very simple. There is a reset switch inside the unit that can be easily accessed. That whole light display thing for diagnostics is very confusing, I still have not figured it all out. They have a PC port to connect to but I think you have to have the Yamaha Service Software or at least a passoword.
 
Yes, I saw it earlier in the thread. Thank you. I think I need to take it in for service. I was able to reset and get the unit to start up again but it seems to only last for a bit before going out. Also I hear what sounds like an actual spark when it starts, sounds like something is arcing right before it goes completely online. So bummed, the unit has served us well for the last 6-7 years.
 
I will be very interested to know what they find. I was able to reset my CPU and it ran fine for a six months and then one day I heard a loud hum out of it and then smoke. I have not tried to service it yet. The smoke came from the right amp board.

What preamp are you using?
 
Wow, that’s not good. I’m using the CX-A5000. The arc/spark I hear sounds like it’s coming from the right side as well. Trying to find a yamaha dealer/servicer to take it in, I may be driving it to Newport Beach or Buena Park, both about 1-2 hours from me in San Diego. No way I’m going to try and ship? I do have original box...
 
Yamaha5000 said:
I am happy to post that I followed the instruction to reset the CPU, now I have full sound. One item still an issue is the cooling fans are not running. Therefore that error code in memory of THM/OLV protection detected excessive heat in the output.
Click to expand...
How did you reset the cpu? I have an MX-A5200 doing the same thing.
 
Drelas said:
How did you reset the cpu? I have an MX-A5200 doing the same thing.
Click to expand...
The MX-A5000 turned into a major nightmare so say the least!

I made a horrible mistake and sent the unit to Buena Park, they completely destroyed the unit. This is a very long story!!!! :rant:

After finally getting the unit back I waited several months (in anger) and then contacted Yamaha Japan Director of Yamaha Audio Worldwide he then put me in touch with the USA Director of Marketing. I did retain all correspondence with Buena Park and was able to show him the complete path. He . was very interested and concerned about what had taken place. I will make this nightmare as short as possible.

After giving him a week to investigate he came back and offered to send me a MX-A5200 FREE OF CHARGE for the all the problems I had experienced, I certainly accepted this most generous offer.
 
You must log in or register to reply here.
Back
Top Bottom