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Discussion Starter #1 (Edited)
Hi all, I am having trouble repairing my Yamaha RX-V667. It initially shut down due to an over current fault which turned out to be a short on a channel (blown transistors etc) and would not go into self diagnostic mode. I repaired the channel and now it turns on for 1 second and turns off. I can now get into self diagnostic mode fine and I can read the fault which is "PS2 PRT 182H", a voltage problem on the power supply. The service manual states that PS2 monitors +5I and -5V and the normal ADC value should be 90 / 88. In diagnostic mode it displays PS2: 112 / 182.

Another thing that I notice is that the voltages out of the transformer are OK, but after they go through the relay on the main board (not the main power relay) they are around double what they should be.

Can anyone shed some light as to where to start looking?

Thanks for any input.
 

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You have to be more specific about what you are measuring and where. When you say voltages are double what they should be, you are probably measuring across + and - and not from each to ground. Regardless, it sounds like you need to determine the problem on the 5 volt supply.

Are you working from a service manual and schematic?
 

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Discussion Starter #3
Thanks for the reply Icaillo,

I have a service manual with schematics.

I having trouble measure the voltage at the 5.0v power supply. It is on the middle board (3 layers) and to power it up and take a measurement while all the boards are assembled is impossible. I have looked for another test point with no luck. It is a NJM2388F05 which appears to have "On/Off" control also, so I need to test that also.

I might just have to remove it and test it on the bench.

BTW, you were sort of correct about my "Double voltage measurements, in my haste I was measuring from the wrong point. :R
 

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Discussion Starter #4
More info....

I have measured the PS2_PRT line and it measures 2.3v. I think that is consistent with the fault message of "PS2 PRT 182H" which suggests that 182 after the ADC calculation (3.3v = 255) = 2.3 volts?

Also +5I measures ~0.8vAC. Is that possible?
 

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I don't know what it should be. It has been years since I service Yamaha receivers and don't recall the labelling. What is +5I supposed to be? Is it an a.c. test point?

If the 3.3v supply is at 2.3v, which is how I read your description, there is likely a shorted or leaky component pulling it down.

Receivers, in general, are very hard to troubleshoot. You have to pretty much know where the test points are that you can get to and where the equivalent points in the circuit are if you cannot get to the component you need to test.
 

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Discussion Starter #6
The 3.3v line is good.

The self diagnostics says that the PS2 fault had a measurement of 182. According to the service manual the the normal reading should be ~90. The 182 and 90 numbers are the digital values of the analogue equivalents. Analogue being referenced to 0 - 3.3 volts and digital 0 - 255. 182 = 2.35 volts and 90 = 1.16 . Well that is at least my understanding of it.

I can't find the voltage regulator associated with the +5I supply.
 

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Discussion Starter #7
I keep reading about a common capacitor problem in the power supplies on yamaha receivers. C405, my unit doesn't have a C405 cap anywhere. All of my capacitors are 4 digit (i.e. C1234)

Can anyone shed some light?
 

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Discussion Starter #8
After crawling the schematic for hours I have found that my model of RX-V667 does not have a +5I power supply fitted, the schematic has a cross through the regulator chip labelled "no_use" and the regulator chip is not on the board. However the diode bridge and a few components are there.

Now to explore the -5V line.
 

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Discussion Starter #9
It's fixed!!!!

The +5v regulator was the culprit.

PS2_PRT monitors +5I and -5V supplies. Th RX-V667 doesn't have a +5I supply so it must have been a -5V supply problem. The -5V supply is dependent on the +5V supply. As the +5V supply was out of spec, replacing the regulator fixed the +5V supply which also enabled the -5V supply to operate correctly.

It now turns on and stays on. It took many hours to get my head around the schematics and the actual PCBs, but $2 later it is all fixed.

Hope this helps someone else.
 

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It's fixed!!!!

The +5v regulator was the culprit.

PS2_PRT monitors +5I and -5V supplies. Th RX-V667 doesn't have a +5I supply so it must have been a -5V supply problem. The -5V supply is dependent on the +5V supply. As the +5V supply was out of spec, replacing the regulator fixed the +5V supply which also enabled the -5V supply to operate correctly.

It now turns on and stays on. It took many hours to get my head around the schematics and the actual PCBs, but $2 later it is all fixed.

Hope this helps someone else.
Do you happen to know/remember what part was the 5 volt regulator?
 

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Hi Folks,

I know this is an old post, but if anyone has any further info on this one, that would be great. My model is the Yamaha RX-A3000, Australian 240V model.

I have a similar problem where the PS2 voltage is out of range (over -at approx 165 or so with range 81-153). I have looked over the PSU PCB and found two 22nF greencaps which I assume are similar in function to the C405 that has been mentioned previously as a big issue with many units, however, both are testing at 22nF.

I've pulled (most) of the unit apart to check for any noticeably damaged components and only found one video IC with some residue which could have been flux or glue, but cleaned it up regardless.

Beyond that, the service manual is a bit vague. I will keep digging to try and find some appropriate test points and values. I'm fairly sure this is going to be a very simple fix once the cause is found, and I don't want to pay $1k or so to get it repaired with a $5 component...

Any guidance on the location and specs of the regulator that was the cause above, or any other advice would be great.
 
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