I've had this for about fifteen years and it has been very lightly used as a TV amplifier in my media room. It is gutsy enough, sounds good to my ears and has a remote - great when watching films / TV.
It has always had a problem of the protection cutting in (out?). Sometimes at random, everytime the sub switches itself on. There are other threads about this here and elsewhere.
Since I am soon to move house I thought I would have it apart and take a look before packing it up. It is very clean inside, has no bulging, dried out or leaking electros and the supply ripple is lower than I would have expected. Overall I don't think it has had more than 1000 hours use in 15 years.
The big negative is that it is almost impossible to get at anything inside! The pic shows the audio side (the other 50% is the DSP and uP controller.
The PCBs are mostly hard-wired to each other with bare TCW jumpers plus the visible ribbon cables. To probe connections underneath would require lifting the whole lot out, including o/p devices on the heatsink! In which case the ribbon cables would not reach!
I have a service sheet which is a bad photocopy which I have carefully re-scanned and blown up and printed out to A2 size! Nightmare! Wires wizzing all over the place and very hard to follow.
A product designed for manufacture and not for servicing!
Anyway, the problem:
The various amp outputs are summed into a classic "protection circuit", which signals the uP. It sends back (or not) a signal to connect / disconnect the power relay. Al the amps have <2mV of offset and the Iq settings are well below maximum ans stable.
Since the sub powering on trips it (same ring main but different socket) and it happens at random at other times I think there is a mains power glitch problem.. Power here is a solid 246V, never varies much and no history of dimming lights, radio interference etc. I have good analog scopes, but chasing one-shot events by powering on/off equipments is not fun.
So I look at the mains connection to the Amp. First surprise is no chassis earth, but it is no-way double insulated, so I'm not sure how that works! The chassis is connected to the amp power rail common (grey wire bottom left) and there are small LV disc ceramics from other places to chassis - typical rf suppression.
I am thinking of adding a IEC mains filter, but that needs a ground for the two output caps, doesn't it?
Can I just add a proper main's earth wire so that a filter will work?
Any other bright ideas how to proceed? Sorry this is so long
BTW, HNY!
It has always had a problem of the protection cutting in (out?). Sometimes at random, everytime the sub switches itself on. There are other threads about this here and elsewhere.
Since I am soon to move house I thought I would have it apart and take a look before packing it up. It is very clean inside, has no bulging, dried out or leaking electros and the supply ripple is lower than I would have expected. Overall I don't think it has had more than 1000 hours use in 15 years.
The big negative is that it is almost impossible to get at anything inside! The pic shows the audio side (the other 50% is the DSP and uP controller.
The PCBs are mostly hard-wired to each other with bare TCW jumpers plus the visible ribbon cables. To probe connections underneath would require lifting the whole lot out, including o/p devices on the heatsink! In which case the ribbon cables would not reach!
I have a service sheet which is a bad photocopy which I have carefully re-scanned and blown up and printed out to A2 size! Nightmare! Wires wizzing all over the place and very hard to follow.
A product designed for manufacture and not for servicing!
Anyway, the problem:
The various amp outputs are summed into a classic "protection circuit", which signals the uP. It sends back (or not) a signal to connect / disconnect the power relay. Al the amps have <2mV of offset and the Iq settings are well below maximum ans stable.
Since the sub powering on trips it (same ring main but different socket) and it happens at random at other times I think there is a mains power glitch problem.. Power here is a solid 246V, never varies much and no history of dimming lights, radio interference etc. I have good analog scopes, but chasing one-shot events by powering on/off equipments is not fun.
So I look at the mains connection to the Amp. First surprise is no chassis earth, but it is no-way double insulated, so I'm not sure how that works! The chassis is connected to the amp power rail common (grey wire bottom left) and there are small LV disc ceramics from other places to chassis - typical rf suppression.
I am thinking of adding a IEC mains filter, but that needs a ground for the two output caps, doesn't it?
Can I just add a proper main's earth wire so that a filter will work?
Any other bright ideas how to proceed? Sorry this is so long
BTW, HNY!
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There may be a fairly simple circuit that detects if the mains voltage is present and correct. If its operation is marginal then any surges/glitches could force it into standby. I've seen this issue a couple of times, one was where a 1uF electrolytic was only reading about 0.9uF so there was nothing really wrong with the cap, it was just a marginal design so I fitted 2.2uF and it's been fine for years now.
Another possibility is a bad signal coming back from the sub amp on power up (DC coupled?). Maybe try to see if it trips with the sub signal cable disconnected?
Not sure what you mean by "bad signal" ....
The sub is connected to the Yam sub o/p, a/c and 200Hz low pass. I think the problem is mains borne, hence the interest in grounding and filtering.
Thanks, anyway.
By bad signal I meant possible dc on the input of the sub amp on start up if the sub amp isn't AC coupled. It's not likely but it is possible.
No.
What happens is that the Sub goes to sleep if there is no signal for a while. If I then insert a CD (for example) and the Yam outputs audio, this triggers the Sub to switch out of standby (relays!) and the Yam drops out.
Now is that a spike up the "ground" wire of the sub to the Yam, or is it mains borne?
I don't know, which is why I am asking about a proper filter (+ground) added to the Yamaha.
Or is it a quick shot of DC when the sub amp turns on? It may be triggering the DC protection circuit in the Yamaha and shutting it down. The AC mains can be verified with an extension cord going to a separate circuit in the house or feeding the sub from a different audio source to see if it it causing mains feed issues when it powers up. It makes more sense to figure out where the problem is originating from before modifying anything.
Leave this line, j, it will go nowhere.
There is only one mains ring available. Nothing else ever gets triggered or zapped or spiked by the sub.
Thanks, anyway.
Do you have any inputs on grounding the Yamaha chassis and fitting a filter?
Bump!
Any views about converting a 2 wire chassis into 3 wire plus mains filter?
I have ordered a couple so I am going to do it, anyway, but would welcome any thoughts.
Any views about converting a 2 wire chassis into 3 wire plus mains filter?
I have ordered a couple so I am going to do it, anyway, but would welcome any thoughts.
Keep the mains filter module outboard...ie in an enclosure with AC socket output.
Mains filter modules contain a Y cap...ie A&N are ac coupled to the earth.
You want to keep these earth noise currents out of the amp, so keep with the standard two wire mains cable.
Dan.
Mains filter modules contain a Y cap...ie A&N are ac coupled to the earth.
You want to keep these earth noise currents out of the amp, so keep with the standard two wire mains cable.
Dan.
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"Mains filter modules contain a Y cap...ie A&N are coupled to the earth"
I know, which is why I asked the question.
I can place the filter such that the filter ground, mains earth wire and only chassis connection are one. Right at the mains earth input.
I know, which is why I asked the question.
I can place the filter such that the filter ground, mains earth wire and only chassis connection are one. Right at the mains earth input.
The metal body of IEC type power inlet filters is connected to the input socket earth pin and output earth wire.
The problem is that putting noise currents to earth will put extra noise currents on the shields of interconnects, and the voltage drop of the shields gets interpreted as valid signal in an unbalanced system such as yours.
There are medical grade versions that omit the Y cap.
Dan.
The problem is that putting noise currents to earth will put extra noise currents on the shields of interconnects, and the voltage drop of the shields gets interpreted as valid signal in an unbalanced system such as yours.
There are medical grade versions that omit the Y cap.
Dan.
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There is no IEC socket. Your assumption.
"The problem is that putting noise currents to earth will put extra noise currents on the shields of interconnects"
I do not see how that follows. What would induce noise to travel down interconnects rather than the earth wire?
Anyway, I'll just try it.
"The problem is that putting noise currents to earth will put extra noise currents on the shields of interconnects"
I do not see how that follows. What would induce noise to travel down interconnects rather than the earth wire?
Anyway, I'll just try it.
I tried it. It works.
I put an inline filter hard grounded to the chassis. Obviously there is now some leakage current to mains earth, but it doesn't seem to matter.
Total absence of triggering when the sub-woofer awakes from sleep.
Looking inside the receiver, I do not understand Class 2 AT ALL! There are many places where a single fault could liven up the chassis!
I put an inline filter hard grounded to the chassis. Obviously there is now some leakage current to mains earth, but it doesn't seem to matter.
Total absence of triggering when the sub-woofer awakes from sleep.
Looking inside the receiver, I do not understand Class 2 AT ALL! There are many places where a single fault could liven up the chassis!
In order to avoid increasing leakage currents (which may provoke annoying ground loop noise upon connecting a grounded appliance like a PC), a mains filter for a Class II device should connect to protective earth only, with no chassis connection. (Ideally there would be double insulation between protective earth and chassis, just in case it ever gets plugged into a badly miswired outlet.) Essentially it doesn't matter much whether the filter is installed inside the device or at the outlet, the mains cable obviously needs to be OK though.
Interesting.
I had read the rules, also, but do not understand how this Yamaha receiver can be so classed! There are mains wires floating around inside without any extra insulation other than that on the wire. Anything disconnecting or unsoldering could easily touch the chassis.
I though there had to be two distinct "layers" of insulation so as to not rely on just one.
Point noted, sgrossklass. There is a couple of mA leakage down the earth wire, as expected, but in my application this does not appear to cause a problem and it solves the problem of the sub-woofer switching on tripping out the receiver.
I had read the rules, also, but do not understand how this Yamaha receiver can be so classed! There are mains wires floating around inside without any extra insulation other than that on the wire. Anything disconnecting or unsoldering could easily touch the chassis.
I though there had to be two distinct "layers" of insulation so as to not rely on just one.
Point noted, sgrossklass. There is a couple of mA leakage down the earth wire, as expected, but in my application this does not appear to cause a problem and it solves the problem of the sub-woofer switching on tripping out the receiver.
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