All I can say about repairing Yamaha stuff most of the time was a nightmare to me. These are over-complicated, the schematics barely readable, all in all of little help at all for people without special Yamaha training.
Didn't check the power amps yet, as I didn't see any hint that they might be faulty, especially no DC voltage at the speaker terminals. And the PRV bus doesn't monitor the power amps.
Best regards!
Best regards!
This is a long shot from experience with a technics amplifier I own. The protection relay in this was quite large and the click was quiet large and would turn on and off at power up. I found by pressing the pcb gently with my index finger at various points around the relay the relay would click on. I suspected a crack in the pcb or a cold solder joint.
There was no crack in the pcb but after applying a little pressure to the relay while remaking solder joints, normal operation was restored. I suspect that continued operation of the relay switching had a mechanical effect which over the life of the amplifier had caused some flexing in the area where the relay solder points connect to the pcb.
Are there are other fault mechanisms other than PRV that trigger protection? Have they been explored? Any way the distinguish between them?
The PRV is "read" by the MCU which then issues a relay order (PRY?) to close the power relay, I don't think the PRV value is used in the protect circuit (need to double check).
Reads like you have a PRV problem, yeah I take the point about manually correcting the PRV, more digging needed.
Try the following.
Pull CB306 measure PRV at W501
Reinsert CB306 pull CB305, measure PRV at W501
Reinsert CB305
The CB305 link should provide no change to the PRV if operating correctly
Pull CB306 measure PRV at W501
Reinsert CB306 pull CB305, measure PRV at W501
Reinsert CB305
The CB305 link should provide no change to the PRV if operating correctly
Question did you measure the dc voltage at the points where the output reaches the input connections to the relay to prove this
The behaviour you described at the outset is typical of a dc speaker protection circuit that is working properly. The speaker terminals are not connected to an amplifier when the powèr is on and there is a dc output fault. There is an initial delay by RC means to avoid popping noise when the power caps charge After that the capacitor will keep the relay closed until power off or another short time delay circuit is actvated to cause the relay to drop out with power on i.e. when excess dc positive or negative dc appears. on the output line. There has to be some summing point for half circuit output stages.
You need to measure inboard of the relay to check this.
You need to measure inboard of the relay to check this.
In #10 I said that I measured some lowish voltages at the speaker leads emenating from the PSU capacitors. But possibly I wasn't clear enough to state that I indeed measured before the relays.
Anyway, in order to allow measurements at all, I had to enter the self diagnosis function with the protection being disabled, according to p. 29 in the SM (pushing the audio mute switch for three seconds and more). This means that all relays were engaged (and lead Yamaha to say to do this with extreme caution). Else the big mains toroid weren't powered.
Best regards!
Anyway, in order to allow measurements at all, I had to enter the self diagnosis function with the protection being disabled, according to p. 29 in the SM (pushing the audio mute switch for three seconds and more). This means that all relays were engaged (and lead Yamaha to say to do this with extreme caution). Else the big mains toroid weren't powered.
Best regards!
I'm trying to understand protection issues.
If we begin with power switch in off state and pull the AC plug briefly to ensure cold start, all looks normal on front panel? Amp is in standby, processor is running, no warning lights? Is PRV abnormally low at this time?
Then when amp is switched on, relays click, meter lights briefly, then protection activates? I'm assuming the amp's logic isn't overly bothered by PRV voltage since it activated relays, then detected a problem and entered standby? Any change in PRV voltage with transitions into protect?
Re PRV, I note that the signal is filtered by 10uF C900, so the processor must expect a DC voltage. You might check C900 to confirm it's neither open, nor that it's leaky which could attenuate the applied voltage.
Does any of this conjecture change perspective about fault mechanism?
If we begin with power switch in off state and pull the AC plug briefly to ensure cold start, all looks normal on front panel? Amp is in standby, processor is running, no warning lights? Is PRV abnormally low at this time?
Then when amp is switched on, relays click, meter lights briefly, then protection activates? I'm assuming the amp's logic isn't overly bothered by PRV voltage since it activated relays, then detected a problem and entered standby? Any change in PRV voltage with transitions into protect?
Re PRV, I note that the signal is filtered by 10uF C900, so the processor must expect a DC voltage. You might check C900 to confirm it's neither open, nor that it's leaky which could attenuate the applied voltage.
Does any of this conjecture change perspective about fault mechanism?
There is a youtube video for an A s 2000 purchased in protect mode. The owner "Tinybench" showed how to reset this .The video is only a month old.
With power off, first rotate the balance control all the way to the right.
While holding the mute button down turn the unit on. The balance light should illuminate. Try repowering unit to see if this clears protect mode light.
If you have not seen this video it is worth looking at.
With power off, first rotate the balance control all the way to the right.
While holding the mute button down turn the unit on. The balance light should illuminate. Try repowering unit to see if this clears protect mode light.
If you have not seen this video it is worth looking at.
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The protection mopde is activated either after the mains it re-plugged with the standby switch on, and when I trow the standby switch with the mains plugged.
I didn't measure PRV voltage yet the way you suggested, but I assume the voltage decreases because the toroid is powered off.
I also had spotted C900 yet, but it proved to be nearly unreachable .This was the reason why I tried to raise the PRV voltage to a value between 0.8 and 1.6 Vdc, but with no outcome. OTOH, from the fact that a very highish 560k resistor, connected to a 20 Vdc rail, was enough to get a bit more than 1 V at PRV, I conclude that C900 isn't leaky at least.
mjona, thank you for the youtube hint. Will check tomorrow.
Best regards!
Does returning the switch to Off clear the blinking LED?
BTW, I like the video suggested by mjona. Would be a painless fix if it works.
BTW, I like the video suggested by mjona. Would be a painless fix if it works.
Yep good pickup, will need to hit the power on button then read instantaneous PRV (before power relay is released).
I'm currently working on a RX-V630 in protect so some of it's terms may slip into your thread.
When plugged in the RX-V goes into a standby state, 12Vdc for relay and 5Vdc to mcu.
What is the PRV of the A-S3000 in STBY state?
When the p-on button is hit the mcu checks it's inputs to see if it's ok to power up then orders the power relay to close, ie, power to main transformer, regulators...
What is the PRV when the power relay first clicks/closes
Pull CB306, PRV after relay click?
Reinsert CB306 pull CB305, measure PRV at W501 after relay click
Reinsert CB305
Trying to work out what branch is causing the abnormal PRV.
Microprocessors can activate protection circuits if there is some glitch in operation like disconnecting or driving an input into overload. This could mess up the processor start up sequence so engagement of the relay is not possible until the micro reboots.
The speaker protection circuit charges apparently have be routed to earth to turn it off through the position of the balance control at turn off.
I think there would be some sensing logic arrangement that keeps the protection operative at power on unless the balance control is oriented as already mentioned and then turned off allowing processor holding charges to be discharged to earth possibly through a micro switch.
Here is the Youtube video link
The speaker protection circuit charges apparently have be routed to earth to turn it off through the position of the balance control at turn off.
I think there would be some sensing logic arrangement that keeps the protection operative at power on unless the balance control is oriented as already mentioned and then turned off allowing processor holding charges to be discharged to earth possibly through a micro switch.
Here is the Youtube video link
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If I interpret correctly, turning on "power" switch activates relays to power the big transformers; the protection circuits detect a fault which prompts processor to immediately disable power and enter protection mode; cycling power switch clears protection and allows repetition ad nauseam/frustration. Please correct me if wrong.
I'm going to propose that PRV may not be the issue. Since you've been able to activate the diagnosis mode (as mentioned in post 29) without provoking further damage, I suggest returning to diagnosis state and looking for fault signals as described in page 27 and especially page 28. I'm subscribing to your suspicion that the problem may be a protection circuit defect rather than circuit being monitored. Maybe a fault state will persist statically in the diagnosis state that is only momentary during the normal power-on sequence. Be alert to the possibility the fault is a glitch at power-on that doesn't get suppressed due to a failed filter time-constant cap. You may have to inspect transient behavior at each trigger path as diagnosis state is initiated. I hope you have a scope!
I'm going to propose that PRV may not be the issue. Since you've been able to activate the diagnosis mode (as mentioned in post 29) without provoking further damage, I suggest returning to diagnosis state and looking for fault signals as described in page 27 and especially page 28. I'm subscribing to your suspicion that the problem may be a protection circuit defect rather than circuit being monitored. Maybe a fault state will persist statically in the diagnosis state that is only momentary during the normal power-on sequence. Be alert to the possibility the fault is a glitch at power-on that doesn't get suppressed due to a failed filter time-constant cap. You may have to inspect transient behavior at each trigger path as diagnosis state is initiated. I hope you have a scope!
If the youtube video solution has not worked the microprocessor firmware could need an update. Looking at page 21 of the service manual for the s3000 there is a description for this download update process. If the present firmware has been corrupted that could be worth invetigation.
The amplifier could be 10 or more years old.
The amplifier could be 10 or more years old.
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Does your amplifier have a CMOS battery ? if so it might need to be replaced. Just a thought after considering possibility your microprocessor might have been designed for a computer but put to another use.
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