Yamaha RX-V373 no voltage on the standby switch

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

That could cause part of the problem, there is a big difference between 4.2Ω and 100Ω, The voltages seen by the micro would be higher with the 4.2Ω so again it would see the wrong voltage and not know what to do. With R229 and R2230 removed, you can check the voltage on CB221 (pins 11,12) and see if it is +3.3 volts (no buttons pushed), If it is +3.3V then the fault is likely with the micro

Look at the schematic, page 88. The voltage is supplied by +3.3M through R1012, you removed R1043 so there is NO way for the voltage to get to the switch PSW+_DET line


If you removed R1042 and R1043, the voltage on the switch side? There is a switch on both sides! With those resistors removed there should be NO current through R1011 or R1012, so there would be NO voltage drop, also there should be +3.3v on one side of R1042/3 and 0 volts on the other side. on both sides of R1011 or R1012 since there IS a voltage drop (2.35v) on R1043, either on of those switches (SW119) is bad, or something on that KEY2 line is dropping the voltage, hopefully your microprocessor key2 input is not causing this.

With R2229 and R2230 removed (and all components placed back on the front panel PCB) I do get a 2.8v and 3.3v on pins 11 and 12 of the cb221 connector.

And on the micro side the volatages are 0.36 and 0.47v...so as said the micro is gone..

What if I get to replace the micro itself.. Any chances... Or it reuquires programming as well..
Or can the current micro be reprogramed..

OR.. Nothing more can be done... And use it for spare parts... Sadly...

[R_J]

Re: Yamaha RX-V373 no voltage on the standby switch

Pins 11 and 12 of CB221 should both be 3.3 volts, the same voltage as +3.3M find out what is causing the one line to only be 2.8v, that might be all that is wrong.
Monitor the line with the 2.8v and press each switch, maybe one switch is bad and causing the problem. If you have to, remove each switch on that line until you get that line back up to the +3.3m voltage.

Study the switch schematic, None of the resistors in the switch circuit have a path to ground, so there will be NO, 0, nada, voltage drop across ANY of the resistors in that switch circuit UNLESS a switch is pushed OR a switch is partially bad (leaky), this does happen.
I will say for the last time, the voltage on each switch (if none are pressed) should be 3.3 volts, not 2.8v

Here is the chart from page 88, it give the voltage value for when the key is pressed, No key pressed will be 3.3 VOLTS
2.8V on KEY1 could indicate INFO button is pressed. 2.8V on KEY2 could indicate TONE CONTROL is pressed

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

That could cause part of the problem, there is a big difference between 4.2Ω and 100Ω, The voltages seen by the micro would be higher with the 4.2Ω so again it would see the wrong voltage and not know what to do. With R229 and R2230 removed, you can check the voltage on CB221 (pins 11,12) and see if it is +3.3 volts (no buttons pushed), If it is +3.3V then the fault is likely with the micro

Look at the schematic, page 88. The voltage is supplied by +3.3M through R1012, you removed R1043 so there is NO way for the voltage to get to the switch PSW+_DET line


If you removed R1042 and R1043, the voltage on the switch side? There is a switch on both sides! With those resistors removed there should be NO current through R1011 or R1012, so there would be NO voltage drop, also there should be +3.3v on one side of R1042/3 and 0 volts on the other side. on both sides of R1011 or R1012 since there IS a voltage drop (2.35v) on R1043, either on of those switches (SW119) is bad, or something on that KEY2 line is dropping the voltage, hopefully your microprocessor key2 input is not causing this.

Hi,

Thank you R_J, I am following you

Here are the updates on the work done till now.

I replaced all the switches to eliminate any doubtful areas but no effect..2.8v remained at it is. Then started removing the resistors one by one from the KEY2 line..R1043, R1041, R1037, and so on but still no success.

Finally removing the R1045 gave the 3.3v on KEY2. (after confirming this, placed the resistors back in the circuit)


With R1045 removed, the power switch has 0v on one side, being at MGND and the other side has 1.04v (PSW_DET). As the next step will have to check, why it is stuck at 1.04v instead of 3.2v, as per the schematics.

Thanks, everyone for your suggestions.

Hemant.

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

Look at page 88, +3.3M is on one side of R1012 Key2 on the other With no keys pressed there will be no current through R1012 (or R1011) so no voltage drop, so the voltage on either Key1 or key2 should also be 3.3v.
But IF one of the keys is pressed all the time, damaged, shorted, then it will cause the voltage to be lower and the microprocessor wont know what to do.
When the power button is pressed, one side of R1045 gets shorted to ground and a voltage divider is set up (22K+2.2K+1.5K+1.5K+1K+1K+10K)
The voltage measured between R1043 and R1012 (Key2) is the voltage the micro sees to understand the power button is pressed. Given the voltage and resistances, when the power button is pressed there should be about a 0.8 volt drop across R1012 so the voltage on Key2 should be about +2.5v with the power button pressed (3.3 when released)

On that same Key2 line, if TONE CONTROL button was pressed the voltage on Key2 would be about +2.65V, so a 1.5v difference between the micro knowing if the power button is pressed or the tone control button is pressed.

If the voltage is already at only 2.3v and not 3.3v the micro will never sense the power button being pressed.

If you check the voltage on the function switches, including power button, it should be ground on one side and +3.3v on the other, check each switch for voltage and if it is zero on both sides that switch is bad.

--------------------------------
Working on the below : from above comments.

When the power button is pressed, one side of R1045 gets shorted to ground and a voltage divider is set up (22K+2.2K+1.5K+1.5K+1K+1K+10K)
The voltage measured between R1043 and R1012 (Key2) is the voltage the micro sees to understand the power button is pressed. Given the voltage and resistances, when the power button is pressed there should be about a 0.8 volt drop across R1012 so the voltage on Key2 should be about +2.5v with the power button pressed (3.3 when released)

--------------------------------------

Will provide the updates about this.

[R_J]

Re: Yamaha RX-V373 no voltage on the standby switch

The PSW_DET line changes to PSW-N_DET on Page 84, it seems to go to two places, one is IC225, pin 91 and also one end of R2296 (100K connected to +3.3M) so maybe something in that reset circuit is causing the problem, hopefully it is not the cpu

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

Hi R_J and All,

Here is the full update, I had a chance to work on it further.

With R2229 and R2230 replaced in the ckt, the voltages changed to the previous value. i.e. on KEY1 is 1.7v (PIN 12 of CB221) and KEY2 is 2.7v (PIN 11 of CB221).

Also, it was found that the voltage at either end of R2235 is at 1.32v. ( R2235 was also replaced as it was showing its in-circuit value as 4.2 ohms, which it was when tested out of the circuit.) but the voltage remained the same.

I have now removed R2274 for isolating, and with the thought that at least now the voltage at the RESET pin (17th of micro) would come up to 3.3v but no it is stuck at 2.65v. I will check the value of R2252 ( in and out of the circuit) and let you know how it goes.

Regards,
Hemant

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

The PSW_DET line changes to PSW-N_DET on Page 84, it seems to go to two places, one is IC225, pin 91 and also one end of R2296 (100K connected to +3.3M) so maybe something in that reset circuit is causing the problem, hopefully, it is not the cpu

PIN 91 has 1.45v and goes to 0v when the power switch is pressed. I will check the value of R2296 (both in and out of ckt) and will let you know.

Regards,
Hemant

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

PIN 91 has 1.45v and goes to 0v when the power switch is pressed. I will check the value of R2296 (both in and out of ckt) and will let you know.

Regards,
Hemant

The value of R2296 is approximately 100K (in ckt).

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

Hi R_J and All,

Here is the full update, I had a chance to work on it further.

With R2229 and R2230 replaced in the ckt, the voltages changed to the previous value. i.e. on KEY1 is 1.7v (PIN 12 of CB221) and KEY2 is 2.7v (PIN 11 of CB221).

Also, it was found that the voltage at either end of R2235 is at 1.32v. ( R2235 was also replaced as it was showing its in-circuit value as 4.2 ohms, which it was when tested out of the circuit.) but the voltage remained the same.

I have now removed R2274 for isolating, and with the thought that at least now the voltage at the RESET pin (17th of micro) would come up to 3.3v but no it is stuck at 2.65v. I will check the value of R2252 ( in and out of the circuit) and let you know how it goes.

Regards,
Hemant

The value of R2252 is near 10K.

[hemant_2222]

Re: Yamaha RX-V373 no voltage on the standby switch

Hi,

Could anyone advice if we can replace the microcontroller directly or it will require to be progeammed as well.

Thanks,
Hemant