Yamaha RX-V473 repair. PS3 PRT: 094L [SOLVED] - Page 1
Forum section: electronics / repair

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 05, 2024, 05:46:28 am
content: I recently bought a second handYamaha RX-V473AV receiver. I bought it as faulty for 40$, after all i only need to replace C405 for it to work... right?It was instantly going into protect mode afer i tried to turn it on, holding down TONE CONTROL, INFO and the power button allowed me to bypass the protect mode and check its history. The only problem that was being reported was PS3 PRT: 094L. The error code PS3 PRT: 094L means that the voltage on pin 106 (5.5V rail voltage monitor) of the IC21 (the processor) is too low. Of course i checked the 22nF cap on the ps board but it was almost perfect (23nF), without any visible ripple on the scope. The PS3_PRT line going into pin 106 is just a voltage divider hooked up to the 5.5V rail, from my calculations the output of the voltage divider should be equal to about 1.96V, and this is (down to the 3rd decimal place) exactly what i measured with my scope. From my understanding the 094L means that the voltage at one point dropped to (3.3/255)*94=1.21V which i think i would notice after turning it on and off a couple times with my scope hooked up to it. Is it possible that the microprocessor is just broken? What do you guys think i should do next?Thanks in advance for any answers guys !!!

author: David_AVD
author_rank: Super Contributor
timestamp: September 05, 2024, 08:32:09 am
content: Check that the sense resistors are still their correct values.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 05, 2024, 08:54:19 am
content: Quote from: David_AVD on September 05, 2024, 08:32:09 amSeems you did not read and understand everything the OP wrote.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 05, 2024, 11:18:04 am
content: normally the PSx is power supply PRT is protection error as guessedi think your problems is elsewhere, in the power supply section(s)

author: wasedadoc
author_rank: Super Contributor
timestamp: September 05, 2024, 12:09:54 pm
content: Which side of R223 are you measuring as 1.96v?

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 05, 2024, 12:54:57 pm
content: you can verify the processor by powering the divider from another 5V supply by disconnecting the upper resistor from original 5v5 rail.maybe you missed some small voltage issue when 5v5 psu is starting (maybe theuP is reading the adc before 5v5 ramps up to 5v5? - for this you need to trigger the scope in normal mode and in respect to processor reset signal, or just do the test i proposed, ask if something is unclear)i doubt processor is wrong but just test

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 05, 2024, 01:01:38 pm
content: Between the microprocessor and the R223 resistor.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 05, 2024, 01:17:01 pm
content: Re: perieanuoI unfortunately dont have a power supply and i also dont have proper gear to solder/desolder smd parts like the resistors in the voltage divider. The thing i hate the most is that i cant really trace where the 5v5 is coming from on the microprocessor board, the board is double sided so tracing gets tricky relaly quick. I checked all the 5v5 inputs coming in to the microprocessor board and they seem fine with 100mVpp ripple at max.I can chcek the power up voltage, although i think i checked it a couple times with single trigger enabled at (-500mV) - (-300mV) and it didnt trigger once. At this point tho its either that or the microprocessor is damaged so i guess im gonna try again.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 05, 2024, 01:27:21 pm
content: Re coromonadalix:The microprocessor is responsible for outputing PS3_PRT when the voltage on pin 106 is abnormal, i measured the voltage directly on pin 106 of the microprocessor and the value is almost perfect.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 05, 2024, 01:34:01 pm
content: I just noticed that there is one more thing connected to pin 106 - LMT_PS3, i attached a screenshot of the origin of that line. Does anybody know what that little transistor circuit accomplishes? PL3.0 comes from another voltage divider hooked up to 3.3S rail.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 05, 2024, 02:58:52 pm
content: The base of Q206 goes to the junction of the top two resistors in the three resistor chain to the above left. If the voltage at that point is low it will pull down the LMT-PS3 line.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 05, 2024, 04:34:49 pm
content: Re:wasedadocCan you dumb it down a bit for me? So when the voltage is too low the transistor opens and drains all the voltage to ground? Why is the PL3.0 there?

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 05, 2024, 07:41:19 pm
content: UPDATE:The self monitor function reacts when i short pins 106 and 105 together, it goes down from 094 to 000. The measurments still show steady 1.96V with almost no ripple (check photo). Also, pin 106 of the CPU is always at 1.96V, even without pressing the power button. Is that normal?

author: David_AVD
author_rank: Super Contributor
timestamp: September 05, 2024, 08:39:46 pm
content: Quote from: wasedadoc on September 05, 2024, 08:54:19 amCan you expand on that? He said there's a PS3 error and I said to check the sense resistors. I probably should have specified I meant the ones associated with the PS3 line sensing?

author: wasedadoc
author_rank: Super Contributor
timestamp: September 05, 2024, 10:16:01 pm
content: Quote from: David_AVD on September 05, 2024, 08:39:46 pmThe OP stated he calculated the expected voltage from the voltage divider. I also got the same result as he provided. He measured the voltage and it was extremely close to the calculated value.

author: David_AVD
author_rank: Super Contributor
timestamp: September 05, 2024, 11:36:06 pm
content: Correct, it measured as expected at the time of the measurement. There are various Yamaha models that have issues with the sense resistors varying in value over time / intermittently. Mostly the ones that use 0603 size SMD resistors, but I have seen it (although rarely) with through hole resistors as well.The other thing to check is the SMPS. I've had units come in where the SMPS controller chip goes intermittent (but not fail completely). I've also seen bad resistors / corrosion in the feedback path around the transistor side of the opto isolator. Lastly, the small electro capacitor next to the SMPS controller chip can go marginal, causing issues.

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 06, 2024, 05:58:19 am
content: Quote from: Comp_Sci_hater on September 05, 2024, 01:17:01 pmput 3 AA batteries in series, that's your 5V, you won't reach the error threshold you calculated before.if you don't have desoldering tools, how do you want to repair this?another users are saying you may have a rogue 5v supply, i'm not alone

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 06, 2024, 12:28:35 pm
content: Re: perieanuoSo i should check if there are really 5.5V coming in to the voltage divider? Im not trying to sound ignorant (im a total noob), but why would i check that, if according to calulcations the voltage out of the divider is spot on? Is there something i am missing?Thanks for replying.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 06, 2024, 02:17:37 pm
content: UPDATE:I just found something big, (i think?) theOPERATION_2board supplies 5.5V toMAIN_4board which then supplies 3.3V to theDIGITAL_2board, where the CPU is located. I dont know how i didnt notice this before, but none of the 3.3V connectors actually supply 3.3V. Here are the measurments:PINEXPECTEDMEASURED+3.3M 3.3V 5.44VDGND 0V 54mVACPWR-DET 3.3V 5.44VCPU-N-RST 3.3V 5.44VPRY 3.2V 4.69VDEST 0.3V 4.49VThis seems all messed up, am i reading the schematics correctly? What could cause this if it is in fact right? I dont know if i should even care about this, the manual says that the 3.3M rail is responsible for the standby led, the remote and the buttons on the front panel and all of these seem to work okay. Attached pictures of all 3 boards. Measurments were taken at the DIGITAL_2 side of the connector with the amp powered up (it was the same with it powered down tho).The 5.5V coming out ofMAIN_4is correct (Measured 5.6V). The PS3 error is really strange considering the PS3_PRT is responsible ONLY for detecting voltage abnormalities on the +5.5V rail.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 06, 2024, 09:54:01 pm
content: UPDATE:The reference voltage given on the manual is wrong (?), it says that 3.3V = 255, but i did a little test that proved this to be wrong. I measured all PS3_PRT, PS2_PRT and PS1_PRT. The values i measured with my scope, and the values being shown on the display are as follows:PSx_PRTDISPLAY [A/D]DISPLAY (USING 3.3V = 255) MEASURED PS1 030 0.388V 0.639VPS2 041 0.530V 0.876VPS3 094 1.216V 2VSo after doing some calculations:30 * x = 0.639 => x = 0.021300041 * x = 0.876 => x = 0.021365994 * x = 2 => x = 0.0212766It all lines up perfectly, is it possible that the A/D conversion is wrong?Guys am i going insane or does this make sense? Until now i used the conversion 255=3.3V =~ 1 = 0.013V, is this wrong?Does this mean that the cpu is getting (255*0.0213=) 5.431V instead of 3.3V as the reference voltage? If that was the case the PS1_PRT and the PS2_PRT voltage would be still within bounds, going from our 255 = 5.43V system back to the 255= 3.3V system we would get:PSx_PRT3.3V = 255 [A/D]BOUNDSPS1 049 12 to 100PS2 068 34 to 106PS3 155 132 to 168I really hope all this is making sense. Please reply with your thoughts.UPDATE:A/D conversion reference voltage is input at pin 2 of IC21, it should be 3.3V, the 3.3V comes from +3.3M rail. Its surely a coincidence, that +3.3M is the same rail that i measured 5.44V on (almost exactly the reference voltage that lines up with the A/D values being displayed on screen), instead of 3.3V.Guys, i think this is it.UPDATE:Everything liens up. The voltage at pin 2 is 5.2V. I need to find out why the 3.3M rail is at 5.43V, and get it back to 3.3V.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 06, 2024, 11:28:47 pm
content: So i found the problem, but i still need to figure out why the3.3Mvoltage is at5.43V. I attached a picture of theMAIN_4board that the3.3Mrail comes from. I would appreciate any help with figuring out which component is failing. I am a total noob so i have no idea what all the circuits related to the3.3Mrail do. Thanks in advance guys!

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 07, 2024, 12:59:06 am
content: I measured all elements on the board, except for the transoptor cause im not sure what i would need to measure. For the transistors i put my multimeter on diode mode and measured across base -> collector and base -> emitter, im not sure if thats how you do it but yeah... ResistorR3009is supposed to be100kohms but im reading9,1kohms, 9.1% of its marked value, i suppose that somehow messes up the whole circuit? Like i mentioned i have no idea what this circuit does. Im going to order a new resistor thats for sure.Check picture for full measurments. Blue on diodes means okay, green on resistors/caps means okay.Let me know if this damaged resistor could make the 3.3V rail sit at 5.43V.

author: David_AVD
author_rank: Super Contributor
timestamp: September 07, 2024, 02:25:13 am
content: The 3.3M voltage comes from another board, not the one in your last post.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 07, 2024, 02:39:06 am
content: OPERATION_2? You can check on previous screenshots that i posted in here.

author: David_AVD
author_rank: Super Contributor
timestamp: September 07, 2024, 06:30:06 am
content: A search for 3.3M in the service manual shows (block diagram on page 75) that it comes from IC25 which is on the digital board. That's the top board with HDMI sockets (page 76). Look next to the factory service connector in the middle of that board, near the front edge.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 07, 2024, 10:56:02 am
content: You're right, i measured the voltages on the IC25 and they are as follows:PIN NRPINEXPECTEDMEASURED4 VDD 5.5V 5.57V3 VOUT 3.3V 5.44V2 GND 0V 0V1 CE/CE 5.5V 5.57VIs the ic gone? there is no input apart from 5.5V so something internally must be messed up i assume.

author: David_AVD
author_rank: Super Contributor
timestamp: September 07, 2024, 11:48:37 am
content: With the unit unplugged from the wall, measure from pin 3 to 4 of IC25 on the Ohms range of your meter.

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 07, 2024, 11:56:24 am
content: It jumps all over the place, it once reached 6M ohms and then started going down for some reason

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 07, 2024, 05:37:55 pm
content: Okay, im looking for a new regulator, i can get the original one but at an astronomical price. And im thinking that i dont really need a low dropout voltage one, because im supplying it with 5.5V anyway. Does anybody have a reccomendation for anygood 3.3V regulators? Would a L1117-33 work well in this case?

author: Comp_Sci_hater
author_rank: Contributor
timestamp: September 16, 2024, 07:49:36 pm
content: UPDATE:I replaced the 3.3V regulator and the amplifier works perfectly!