YAMAHA HTR-5230RDS randomly switches off (PS PRT error)

[calin_ionesco]

Hello,
I've been looking at other posts on the forum related to yamaha PS-PRT errors but I'm a bit of a noob in electronics and they seem to be similar but I still have a hard time getting my head around it. Hope you guys can point me in the right direction.
so my YAMAHA HTR-5230RDS has been working flawlessly for years and starting about a year ago, it would just switch off (with no real explanation). When I try to switch it back on again, it clicks, lights up the display then switches off in about a second. If I leave it switched off for a couple of days, after I switch it back on, it works fine for weeks or months.

I tried to debug, but obviously, as is the case with most of these issues, the fault disappears once I unplug everything and move it.

I looked at the service manual (https://manualzz.com/doc/1076378/yamaha-htr-5230rds-service-manual) and I tried the diagnostics.
Everything works fine after I moved it, but I do have a PSPRT 40% error just after starting the diagnostics (this would be the last recorded fault and I'm guessing that's where I should start looking).


When I run the diagnostics on the bench, the value for PS (page 17 of the manual) oscillates between 30 and 31 - normal and I have no idea how to reproduce the error (as it's as random as it gets... high volume, low volume, hot, cold, etc... and quite rare - every other week or every month). And if I move the unit, it comes back to life.

So, My questions to this esteemed community:

1) How can I reproduce the fault or do I just have to use it until the fault occurs again and test without moving the unit?
2) Is there anything I could check while the unit works fine that might tell me what's going on?
3) How do I interpret the PSPRT 40% error? Manual says 5V/100%. So it saw 2V somewhere instead of 5 and that's why it activated the protection?

[kawal]

I had a problem like this on a different yamaha model . The issue for me was a defective 5v regulator and after it was replaced the problem is resolved. The regulators run hot. In your case I would resolder the pins of all the regulators as heat cycling can crack solder joints. The hard part about troubleshooting is catching the actual event and getting to measure all the rails while there is a fault. Most of the rails are tied together to one analog input on the processor and have only a small contribution to the result displayed. The last is the reason why you need to measure the voltages while you have a fault condition.
If I recall the voltage regulator that failed in my unit was obsolete but I found an equivalent with the  same pinout.
But looking at the schematic you provided the regulators are the 3 pin type which are widely available.
Don't rush into it.
Hope that helps.

[calin_ionesco]

Thanks,

I think I'm going to put it back in use and wait for the fault to appear again.. My girl won't be very happy with a half open amp, but it's the only way I see to get an accurate reading. If I won't get some strange voltages while the faults occur directly on the regulators, I'll go the long way and resolder them all.

[calin_ionesco]

Yes, I've taken off the front cover in order to spray some contact cleaner on the volume control. Is it a variable resistor or potentiometer? I'm not too familliar with the english names of electronic parts. So I'm all set to check the voltages next time it breaks. Yes, my girlfriend got the safety talk

[mzacharias]

It's not 40%.

Yamaha does it like this:

5 / 256 = .01953125

This x 40 (the value given) = .78125

This is approximately the voltage seen by the microprocessor at it's protect input, so the actual range of 30 to 31 should represent more like .5859 volts at that node.

Why they do it this way I don't know; newer models use 3.3 volts as the reference instead of 5V.

[kawal]

That pot has 6 layers for 6 channels.  You need to get to the back of it to clean it well