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Yamaha MX-A5000 service issues

Yamaha5000 said:
Of course the next step is to determine where the fans get their power from
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Page 68 power supply. One for each fan. Only thing common to both is the fan control signal from the CPU and bridged rectifier D109.

Check for 31 vdc at the bridged rectifiers DC connection.
 
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From what I can see if the Bridged Rectifier had issues many other functions would also have issues. The CPU may very well monitor the heat on heat sink and when a certain level of heat is detected the fans come on? I would have thought that the run all the time.
 
Yamaha5000 said:
From what I can see if the Bridged Rectifier had issues many other functions would also have issues.
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KEY !!! is the 31 vdc off D109 getting to the fan controllers circuitry D103 and D104..????? Regardless how the fans are supposed to operate. If its not getting there ,the fans will not operate.

ie. cracked solder connection, broken wiring etc.
 
Be careful with meter leads in the live amp, grabber connectors are useful and I try to connect them and set the meter before turning the amp on.
If voltage is good, I'd check the fan/s are actually still functional, you could apply their rated or slightly lower voltage (eg. battery, with the amp off and fans ideally disconnected) to make sure.
 
zaibatsu said:
Be careful with meter leads in the live amp, grabber connectors are useful and I try to connect them and set the meter before turning the amp on.
If voltage is good, I'd check the fan/s are actually still functional, you could apply their rated or slightly lower voltage (eg. battery, with the amp off and fans ideally disconnected) to make sure.
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I received my DVM and took a couple measurements:
@ D103 33V
@R108 32.7V
@Fan +0.9V
@FANL_PRT 0.00V
@Fan o 0.00V
 
avionic said:
Page 68 power supply. One for each fan. Only thing common to both is the fan control signal from the CPU and bridged rectifier D109.

Check for 31 vdc at the bridged rectifiers DC connection.
Click to expand...

Thank you. I am a little concerned about the exact placement of the probes
 
avionic said:
Is 5v standby getting to the collector of Q815?
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Getting to Q815 is a very big challenge. I was able to look at W124 +5STBY and have 5v. I don't know if that is the same?

I took a hairdryer out and put it on the output heatsinks, just to see if a little heat would turn the fans on. It didn't help. I did notice the Left Channel fan motor turned very easily, the Right Channel fan would turn but required a greater air pressure and the moment to air was removed it stop turning.
 
avionic said:
KEY !!! is the 31 vdc off D109 getting to the fan controllers circuitry D103 and D104..????? Regardless how the fans are supposed to operate. If its not getting there ,the fans will not operate.

ie. cracked solder connection, broken wiring etc.
Click to expand...

Going back to D109:
- terminal to ground = 22.67v
+ terminal to ground = 33v
C113 connection @ bridge to ground = 24.64v
C114 connection @ bridge to ground = 24.64v
 
Yamaha5000 said:
+ Probe on + and - Probe on - the voltage is 55v
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I believe it is obvious this unit has service issues. Due to it's high cost I don't want to fool around and create further damage. Any chance of me shipping the unit to you for bench repair?
 
Yamaha5000 said:
I believe it is obvious this unit has service issues. Due to it's high cost I don't want to fool around and create further damage. Any chance of me shipping the unit to you for bench repair?
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No...To new. I work on the older, non-HT tuff.
 
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