Yamaha RX-V373 no voltage on the standby switch

[hemant_2222]

Hello everyone,

Could someone please advise on this. I have this Yamaha taken from a friend for repair, especially since it had a USB for my interest. But it is not working at all.

Here is what has been done so far. Checking the standby switch did not show 3.3 volts on one of its pins, the other was ground. it is showing as 0.60 volts. I have changed the switch as it had some resistance even when normally open. After changing the switch, I next saw that PIN 91 is not showing 3.3 volts.

The processor clock pin show 2.8 on pin 18 (XOUT) and 0.80 on pin 20 (XIN). I am not sure if the processor itself is not working.

Next, the CB 221 connector did not have +3.3M present on it due to bad connector pin contact with the flat cable. I did press it with a needle and now at least it shows 3.3 volts.

Any suggestions/ideas or different ways will be helpful to me.

Thank you for reading this,
Hemant


I have attached the service manual for referance.

[hemant_2222]

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

Hi All,

Here are a few more updates on this issue, please if anyone could share any other way of troubleshooting, I think I am getting stuck in this.

I removed R2235 for narrowing my measurements and found that the pad on the connector (CB221) end shows 2.38 volts and the CPU board still shows 0.60 like before confirming that the issue lies on the CPU board.

Then following the schematic I also checked (out of the circuit) R2296, D2204, D2203, D2202, and R2289, they all measured up to their marked values.

I am looking for the voltage value that should be present under normal conditions, at the RESET pin17 of the microprocessor.

Looking for assistance.

Regards,
Hemant

[R_J]

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

I believe the /RESET pin should be high, When first plugged in and the cpu gets +3.3M Reset will go from Low to high, this happens fast.

[redwire]

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

You might have a stuck keyboard button?
Power switch SW171 -> PSW_DET -> keyboard on OPERATION (1) -> CB221 as analog voltage KEY2 CPU pin 124 2.34-2.54V pressed. It should be high 3.3V with no button pressed.
PSW_N_DET should be high 3.3V
Next I would check 3D_PON CPU pin 84, R2253 to see if the CPU is turning on the +3.3D supply. +3.3M should always be up.

[hemant_2222]

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

Thanks R_J,

With the fact you stated, I removed the IC223 (Schmitt trigger buffer) and now the voltage at the input pin 2 is 1.23V and output at 2.36v, with the IC removed. Now pin 91 (PSW_N_DET) is also showing as 2.43v, which was also almost zero volts before this.

I am not sure if I'll be getting this buffer anytime soon but I will update the case here.

With Redwire's comments for SW171, as the IC223 is removed now, I will update it once I place the IC back there.

Thank you guys, for your input.

Regards,
Hemant.

[hemant_2222]

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

Hi All,

Hope everyone is doing well.
After a long time, I had an opportunity to work on this unit again. Now the IC223 is replaced but there is no change in the behavior. But, when the power key is kept pressed for a longer duration, the voltage at the input drops and then there is a change in the output of this IC. i.e. the o/p changes from initial 2.45 to 0.24v. Low to pin 17/reset of MCU.

Hey @redwire. Here are the measurements that you requested,
CPU pin 84 is always 0.33v in spite of pressing the power key for a longer duration.
CPU pin 124 is at 1.7v (not pressed) and 1.6v (pressed)

Pressing the keys to enter the diagnostic mode has no effect.

The long press of the power key seems to discharge and reach to a level at which the Schmitt trigger fires up, but don't know why it is taking longer and not instantly. Is there a charge/discharge circuit (comprising of D2204 and R2289) that needs to be looked at.

Expert comments please.

Thank you,
Hemant

[hemant_2222]

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

Any further things to be checked, so that the power relay is turned on.

[lotas]

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

Did you do a reset?

[R_J]

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

the CB 221 connector did not have +3.3M present on it due to bad connector pin contact with the flat cable. I did press it with a needle and now at least it shows 3.3 volts.

Didi you actually repair the connection? pressing it with a needle is hardly a repair, You likely are missing or have a low +3.3M, The power key etc. supply a voltage on key1 or key2 based on the +3.3M voltage, this voltage can not be low or the micro will not know which button is pressed.

[hemant_2222]

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

Hi,

I have replaced the PFC cable and also tweaked the corresponding connector contact on CB221, ensuring it is in proper contact. Here are some of the voltages before (U) and after the key press (P), at CB221:

+3.3M = 3.3v (U/P)
KEY1 = 2.3v (U) and when pressed give random voltages.
KEY2 = 2.3v (U) and when pressed give random voltages.
PSW_N_DET : 1.4/0v

If you need any more voltage measurements for this connector, please let me know so I can note those down.

Any suggestions from the above information?

Thanks

[hemant_2222]

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

Did you do a reset?

No resets yet as the unit of totally down. No relay clicks at all.

[lotas]

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

No resets yet as the unit of totally down. No relay clicks at all.

The relay will not click if it is fully blocked.
Try this: connect to the network (220v) hold down the "TONE CONTROL" and "STRAGHT" buttons and press "POWER"

[hemant_2222]

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

The relay will not click if it is fully blocked.
Try this: connect to the network (220v) hold down the "TONE CONTROL" and "STRAGHT" buttons and press "POWER"

Yes, I tried the above but it is not working. No relay click.

[hemant_2222]

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

Didi you actually repair the connection? pressing it with a needle is hardly a repair, You likely are missing or have a low +3.3M, The power key etc. supply a voltage on key1 or key2 based on the +3.3M voltage, this voltage can not be low or the micro will not know which button is pressed.

I have ensured that the voltages are reaching the pins of key1 and key2. How much it should be ideally? It measures 2.3v in ideal conditions and when keys are pressed, the voltages drop, which are different for different keys.

What next can be checked, Any suggestions?

[lotas]

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

Yes, I tried the above but it is not working. No relay click.

Then try like this:
Unplug the receiver

Hold down the "TONE CONTROL" and "INFO" buttons

Then connect the receiver to the network

And then press the "Power" button and hold all 3 buttons for at least 3 seconds

[R_J]

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

I have ensured that the voltages are reaching the pins of key1 and key2. How much it should be ideally? It measures 2.3v in ideal conditions and when keys are pressed, the voltages drop, which are different for different keys.

What next can be checked, Any suggestions?

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.

[hemant_2222]

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

Then try like this:
Unplug the receiver

Hold down the "TONE CONTROL" and "INFO" buttons

Then connect the receiver to the network

And then press the "Power" button and hold all 3 buttons for at least 3 seconds

I don't think it will do any change.

[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.

Super explanation. I will try this all soon.

Considering the above detail, I removed R1042 and R1043 for isolation, the voltage on the other side (switches side) of the resistors is now 3.01 and 2.35v respectively. I will check more on this and update soon.

What should be the voltage at the main power switch. It is now at 1.4v in normal condition.

[hemant_2222]

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

Another information that I would like to add here is, I had removed R2229 and R2230, again for isolating, but it was lost (being micro in nature) so I had it replaced with 4.2 ohms of small resistance in its place. Would that make much of a difference in the operation. I know it was foolish of me

[R_J]

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

What should be the voltage at the main power switch. It is now at 1.4v in normal condition.

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

I removed R1042 and R1043 for isolation, the voltage on the other side (switches side) of the resistors is now 3.01 and 2.35v respectively

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.