|
|
Post by mastertech on Nov 27, 2015 17:08:03 GMT -5
No, you cannot just remove the eeprom and test. Without an eeprom the unit would be dead, which it is. That is why I said the eeprom could be one of the problems. So that would not be a valid test. And no you cannot replace the MPU with a blank one. It must have it's firmware preinstalled and Yamaha does not sell them. So replacing the complete board, if one is available, or finding a used receiver that is damaged would be the only options if it were the MPU.
Control lines are any lines that send data. There are lots.
Is the MPU accessable for testing when the unit is fully assembled?
|
|
|
|
Post by masterdoor on Nov 28, 2015 9:32:36 GMT -5
|
|
|
|
Post by mastertech on Nov 28, 2015 11:49:26 GMT -5
Missed that one  Checked: IC98 3.3V MPU IC81: 3.3V on pin 25,69,115,164,170,171,174,175 This response has me confused. Did you check the output of ic98? It is not what powers the pins you listed. |
|
|
|
Post by masterdoor on Nov 28, 2015 16:30:27 GMT -5
Yes, IC98 has 3.3V output.
Sorry about the confusion. I know it's not IC98 that powers MPU on those pins.
It was just another step in the problemsolving.
|
|
|
|
Post by mastertech on Nov 28, 2015 17:42:52 GMT -5
It is hard to say if the eeprom is programmed or not but if the document is correct then it is probably not. But ic82 is programmed, which is a flash memory device which also controls ic84 and ic85 flip flops. The list just keeps growing that can cause a processor to not respond to anything.
What I would try is this. For this all boards and harnesses must be attached. Receiver will be unplugged. DMM on diode scale and the neg probe attached to a good D_gnd. I would then use the positive probe to check all pins on the MCU, Eeprom, flash memory ic, flip flops and any other controlling ic, looking for readings of .1xx or lower and write down pin numbers with these low readings. Then we can look over and see if there is a good reason to be low or not.
The fact that the MCU crystal is running is telling me the MCU is not completely dead.
|
|
|
|
Post by masterdoor on Dec 6, 2015 10:36:25 GMT -5
Pins that shorts to ground:
IC81: Pin 14,23,67,117,162,172
IC84 and IC85: Pin 10
IC89: Pin 6,7,8
IC82: Pin 27,46
|
|
|
|
Post by mastertech on Dec 6, 2015 22:17:27 GMT -5
How about that eeprom? If it is still removed put neg probe on pin 4 and test all other pins with pos probe looking for a low reading, .200 or less.
|
|
|
|
Post by masterdoor on Dec 8, 2015 11:33:28 GMT -5
It's still removed. No low readings. Mostly 0.8V. I think this unit will serve as spareparts. If i understand you correct, MCU needs special firmware that Yamaha does not provide. If thats correct, theres nothing i can do exept change digital board  THANKS for all your help in troubleshooting. Much appreciated! |
|
|
|
Post by mastertech on Dec 8, 2015 12:41:35 GMT -5
Yes, correct on that MCU. I have seen quite a few Yamahas that seem to end up with a bad MCU. It's a shame really that the ic is not available.
|
|
nashou
Unmoderated Off Topic
Tech in Training.....
Posts: 1,239 
|
Post by nashou on Dec 29, 2015 23:36:51 GMT -5
Just like my 671 Nashou |
|
OK, thanks for the info.
