Yamaha RX V1067 talk

[crashbunny]

Hi, if you don't like long rambles, you won't like this post.                 
                                                                         
I'm just getting started learning electronic repair for a hobby. My first
 kill, I bought a complete but faulty bose system for $30, it was easy to work on and an easy to find fault, blown MOV and fuse, no shorts found on the board, no other physical issues like leaking or bulging caps, replaced them and it works. yay. exciting.                                   
                                                                         
brimming with confidence I bought the v1067 for $35. https://www.manualsl
ib.com/manual/1104848/Yamaha-Rx-V1067.html#product-RX-V1067 .This is going to be fun, but, so many boards, different types of screws, cables, ribbon cables, i've taken lots of photos but I can't see myself getting this back together, I think it's going to look like homer simpson's diy bbq in the end.                                                               
                                                                         
I did have some clear and concise questions, but as I was writing them, I
 started thinking some more, looking things up, and ended up answering them myself with 80% confidence. (I wish it was 100%) This is more of a brain dump to help me think, and if you see I've dumped some emu poo, please jump in.                                                               
                                                                         
The rub is, the unit powers on, I couldn't get any sound out of it and it powers off, sometimes straight away, sometimes after 5 minutes. When it's on and I'm trying to get some sound out of it, it says something like DSP OFF.                                                                 
                                                                         
After it turns off, if I go into the service menu, the error I get is   
                                                                         
PS PRT : 3 L                                                             
                                                                         
this confused me because all the errors I've seen in the forums have PS1
rather than PS, so I wondered if the 3 meant PS3, but I don't think so now.         

because in the history, it's                                             
                                                                         
PS1 3                                                                   
                                                                         
I believe that's a protection circuit kicking in (PS1_PRT). I think the 3
 is v3.3 / 255 * 3.                                                     
                                                                         
basically a short, but, it's not there all the time. when first turned on
, PS1 is within range, until it isn't some random time later.           
                                                                         
I believe PS1_PRT is a circuit or bus or whatever that appears on many boards, and any of those boards can trigger the protection. I'm thinking basically all the boards can trigger PS1_PRT since they are probably powered by a board that has PS1_PRT.                                           
                                                                         
The manual says                                                         
                                                                         
PS1: +3.3s, ACBL, ACM1, ACM2, +5, DCDC, -3.3V, +3.3HDR (U model)         
(Reference voltage: 3.3 V=255)                                           
                                                                         
I have no idea what ACBL, ACM1, ACM2 or DCDC refers to, this is the only spot they appear in the manual.                                         
                                                                         
Considering the protection doesn't typically kick in straight away, sometimes it's 10 seconds, sometimes 5 minutes, I'm thinking it's not the output transistors.

Considering there's no audio along with the DSP OFF message, I'm thinking the fault (or one of the faults) is going to be on a board that processes the audio before being amplified. Maybe the board DIGITAL(1) which has PS1_PRT and a DSP. For me, that's the worse possible board. lots of surface mount components with ICs with tiny pins. There's no way I can measure a voltage on a pin of an IC without slipping and shorting something.   
                                                                         
I've done a quick in circuit diode test of the main output transistors and they all seem fine, no shorts, no odd one out, they all read the same. I've given the electrolytic caps a quick ocular pat down, nothing stood out as obviously faulty.                                                 
                                                                         
So now I think I'm going to more closely look at some boards and measure some resistance, test some transistors and diodes. Look for physical issues like leaks, bulges and burns.                                       
                                                                         
After I've wasted enough time doing that and not finding anything, I think I'm going to have to power it up while apart and do some measuring. I'm hoping the fault is always there (considering the DSP OFF message), I'm not sure why the protection circuit seems to kick in randomly, though.   
                                                                         
You're still here? If you have any thoughts, please share.               
                                                                         
         

[Swake]

faulty bose system -> Yamaha-Rx-V1067

Yeah, that's kind of a jump 
With a bit of luck it will be the cheapest learning money you could spend, maximum bang for the bucks.

Considering the protection doesn't typically kick in straight away, sometimes it's 10 seconds, sometimes 5 minutes, I'm thinking it's not the output transistors.

Also considering it is a digital system, these are more sensitive to power supply anomalies, therefor I would start with that part. Measuring everything and scoping to find eventual excessive ripple. Don't know about the quality of the caps in the Yamaha's, worth checking them anyway, preferably out of circuit.

It might also be related to something heating up more than it should. If you have no thermal camera you could use the old trick with alcohol or lighter fluid that is evaporating quickly in heated places.

There's no way I can measure a voltage on a pin of an IC without slipping and shorting something.

That pin is going to be connected to something else. Sometimes it is easier to probe that other thing. Or else you could solder a wire somewhere down the pcb track.

Is there a real power on button or is it having kinda an always on stand-by feature? Would be the first device with an issue in this region.

Try to make the difference between symptoms of the fault (you care but not that much) and what is the real root cause of the fault.


ps: Do NOT connect your good speakers on it. Do connect some scrap recovered ones. If things go south the speakers might release the stored smoke quicker that you could realize it.

[crashbunny]

thanks for the reply.

I've got cheap speakers connected to it.

Yeah, that's kind of a jump 
With a bit of luck it will be the cheapest learning money you could spend, maximum bang for the bucks.

hopefully no bang. there's more than $35 worth of parts in it, but, yeah, it's confronting just looking at it, it's a jump.

Also considering it is a digital system, these are more sensitive to power supply anomalies, therefor I would start with that part. Measuring everything and scoping to find eventual excessive ripple. Don't know about the quality of the caps in the Yamaha's, worth checking them anyway, preferably out of circuit.

It might also be related to something heating up more than it should. If you have no thermal camera you could use the old trick with alcohol or lighter fluid that is evaporating quickly in heated places.

cheers. I've seen people use thermal cameras, alcohol and flux vapours. Thermal camera is on the wish list.

Is there a real power on button or is it having kinda an always on stand-by feature? Would be the first device with an issue in this region.

no real power button. I'm thinking the standby power supply is not a problem with this unit, but i'll definitely add it towards the end of the list of things I want to check.

Try to make the difference between symptoms of the fault (you care but not that much) and what is the real root cause of the fault.

I realised I can't just randomly measure things. I think looking for physical issues, looking with a thermal camera is good. but I need to narrow down where I want to start measuring first. I need to come up with a possible root cause that would explain the symptoms, and then rule it out, or in. I said in my original post I thought it was the board that processes audio, and...

I've done some more research, I think DSP OFF is a common fault with the DTS chip, that would explain the no sound, but, I'm not sure that explains the power protection circuit randomly kicking in. I suppose the DTS chip could be randomly shorting when it warms up, but that is a different symptom to the video I just watched.



it's an interesting video, he has the unit on and trying to play but there's no sound, he then heats up the DTS chip with some hot air and sound starts playing, then he cools the chip with an aerosol can and the sound stops. The big difference is my unit is going into power protection and his isn't.

Apparently there was a bad batch of DTS chips and many yamaha's fail with the same problem after x years, and the DTS chips aren't sold to the public.

[rfengg]

"Apparently there was a bad batch of DTS chips and many yamaha's fail with the same problem after x years, and the DTS chips aren't sold to the public."

Unfortunately the TI DSP chip in question, was responsible for audio failure not only in Yamaha, but also in Pioneer, Onkyo, Integra and other receivers....the protect would not kick in afaik due to the DSP chip itself.

Does the speaker block come up on the display for you? If the protect is kicking in, its unlikely the DSP chip but rather something on the power amp stages.

[Swake]

Look into the power supplies first. Big chance the protection kicking in is not the root cause but a consequence.
The fact there is a service menu means the main CPU is ok and doing it's job. That specific power supply might work as expected, or not.
Measuring (ripple) is knowing.