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What damage have I done?

Moonlight

Standard Member
Hi

I have a Denon AVR 2105 receiver, and whilst trying out a different pair of front speakers I heard a fairly loud 'pop' shortly after the sound started when the sub kicked in. The receiver switched to protection mode and the power light started flashing. I checked the manual under 'troubleshooting' where it says 'Display not lit and power indicator is flashing rapidly' > speaker terminals are short circuited.

I checked the connections and damn…I had the wires around the wrong way on the receiver. After switching them around and trying it again, it kept going back to 'protection mode' / display off..flashing power light.

In the old days it might have been a blown fuse, but there is no external fuse to check.

I then tried 'initialization of the Microprocessor (reset') with no luck.

Waited a while for it to cool down, not that it was hot or even warm to touch, and tried again…no luck there either…I was hoping the pop might have been the internal protection kicking in and that once the wires were reconnected correctly…it would reset itself and work…..nup.

Ok…..any ideas as to what damage might have been done?….as it seems like a trip to the repairer. Does it sound like a major job…as I'm wondering whether I am going to pay dearly for my blunder??

Any assistance with this would be appreciated

Cheers
:oops:
 

sennen

Established Member
Have you tried unplugging/turning off the power at the wall socket and waiting a short while before powering up again. Just going to/from standby might not be enough to reset the trip.
 

Moonlight

Standard Member
Thanks for the reply sennen.

I had been turning the power off at the Belkin powerboard, not the actual point.
I rang a Tech who's fixing another receiver of mine under warranty, and after talking him into a rough idea of the damage and repair bill, he said I'd probably blown the output and possibly burnt out other things. He said the output thing costs $30 and may take a couple of hours on it, both to get in, replace bits and then do all the testing to make sure it all works and is balanced in all the channels, workings etc.

Said cost would be at least lower $200s and possibly more. I took this as more like $300+ and then add $25 courier each way and the repair bill would total around what I paid for it $390.

Instead of paying that, I opted to go for a used 3802 model on eBay….like why not…they're made in Japan (I think) and not China like the 2105 and 110w/ch instead of 90. Well…it made more sense to me to replace it.

Fingers crossed the guy isn't selling me a dud:lease:
 

Paul Stimpson

Standard Member
Hi Moonlight,

Unplug the amp from the mains and wait 5 minutes to make sure it is fully discharged. Disconnect all the source and speaker cables from the back of the amp then plug it back into the mains. Does it power up OK then? ((can someone please confirm the Denon doesn't do anything strange if it doesn't have any speakers attached?)) If it goes into protection mode with no cables in it then you know it's the amp that has the problem. If it powers up fine without the speakers then that tends to suggest that you have a bad speaker cable/speaker. If that is the case I would power off, reconnect a speaker then power on and test until you find the speaker that causes it to fall over.

Are you using the same cables for the new speakers you were for the old ones? Could you have a pinched/damaged cable (which would keep it tripping)? Do you have a test meter? If so disconect all the speaker cables at *both* ends, make sure the wires aren't touching at either end and do a resistance test. You should get no reading from any of them. If you do then the cable is damaged and shorted.

I would suggest you examine the speaker terminals on the back of the amp carefully. Are any of them cracked/wobbly/loose? If one of them has shorted to the amp case then that would probably trip it. Look at them very closely with a torch (and a magnifying glass if necessary.) Has a strand of copper from one of the cables broken off and shorted two of the terminals together? Check this on the back of the speakers too.

Let us know how you get on.

Good luck,
Paul.
 
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Moonlight

Standard Member
Thanks Paul

It was the same cables when trying the other speakers.

I unplugged it from the Belkin powerboard so that nothing else (DVD etc) was connected and plugged directly into the main.
After taking out all the speaker wiring turned the power on and turned on the receiver.

It went into protection mode, flashing power light.

Seems like it is the receiver. The Tech I spoke to said that the protection is to protect the speakers but only works to a point.

It popped when the really low keyboard sub bass kicked in, so I'm guessing that would be a pretty severe wallop when the wires were connected the wrong way on the receiver.

Good that you pointed out disconnecting the speaker wiring.
Definitely worth a try so much appreciated.
 
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Paul Stimpson

Standard Member
Hi,

Sorry it doesn't look good. Just one thought... Do you have a cheap amp you could test the speakers on to make sure the speakers are OK and a faulty speaker didn't do the damage before you plug them into your new toy?

Cheers,
Paul.
 

Moonlight

Standard Member
Yeah I do…good idea, although it doesn't cater for a sub or two.

I have a Tech friend that thinks all that would be damaged is the output transistor.
The other Tech I spoke to at RTD Services in North Geelong also mentioned this, although naturally kept the option open that more damage could have been done….?
 
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Paul Stimpson

Standard Member
The output power transistors are the things that handle the high currents that drive the speakers. In many amp circuits they come in pairs with every speaker output having a pair. If the amp is tripping it is probably one of those as gone short. When that happens the other transistor of the pair usually gets destroyed too so you should always change them in pairs. The two most likely things to have happened are that you have blown one or more pairs of transistors or cooked the power supply though I think the transistors are the prime suspects.

The other reason for changing pairs is that the two devices should be "matched". There are variations between devices but companies that deal with transistors for amplifiers will usually offer "matched pairs" of devices with the same curves that will amplify correctly together for a higher price than two random devices.

If your friend is handy with a soldering iron he may be able to remove the transistors (making sure they remain matched pairs and don't get mixed up). He should be able to identify failed devices. I expect that you will find one or two failed pairs if the speakers were connected incorrectly. I'd start with the sub drive pair and whichever pair that drive the speaker you accidentally connected the second sub wire to.

Depending on the types of devices you may well find that replacing the blown pairs is a cheaper than the official repair. Unless you have access to the service manual for the amp you will be limited to changing the devices. It will probably work well enough but you won't have the factory calibration procedures to be able to certify its performance is 100% with the original spec. I found a place here selling pairs of transistors (which will probably be the ones you need. AVR2105 2SB1560Y+2SD2390 Transistors Denon At US$50 (or so) a pop (excuse the pun), if it was my amp and there were 3 blown pairs or less I would probably fix it.

Does the amp pass the "nose test"? If you sniff at the vents do you smell burning? (what we refer to as a "brown smell") ;)

Let me know how you get on,
Paul.
 
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Moonlight

Standard Member
I didn't smell anything although I didn't check at the time.

My Tech mate doesn't think that the wrong wiring should have blown the transistors (may have to read again)
and believes that it must be due to something else going wrong? He suggested starting from scratch as I probably haven't got it wired up correctly.

I've posted in another forum asking about whether it should switch to protection mode after turning the power on when no speaker cables are connected. Asking whether this is 'normal?'

The cheapy Onkyo amp hasn't got a sub input and I need to check the sub and it's cable.
Another receiver I have is an Onkyo 7.1 and a Pioneer 5.1 which I'm reluctant to use with the dubious sub in case it blows it….and they are reasonably good receivers although each only cost about $100 on eBay.

I've picked up the 3802 receiver and don't want to take the risk of damaging it either, so it's a bit of a dilemma atm.

The other option is to test the other speakers on the cheapy throw away and only use the one sub until I get the other checked out?

A guy on the other forum said that it it is likely that when using 2 of the same model subs, that there will likely be a difference in the volume…..due to the input?

I'm getting a bit paranoid now…not to damage more receivers cause they would just get thrown away….like watching $100 notes go up in flames…..
 
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Paul Stimpson

Standard Member
I didn't smell anything although I didn't check at the time.

In some ways I was hoping you would say you could smell burning. Those are plastic-bodied transistors and if they get abused badly enough they tend to shatter. It makes working out which device has failed quite easy (it's the one with the big hole in it ;) )

My Tech mate doesn't think that the wrong wiring should have blown the transistors (may have to read again)
and believes that it must be due to something else going wrong? He suggested starting from scratch as I probably haven't got it wired up correctly.

I understand what your friend is saying but as it's tripping when there's nothing plugged in I respectfully disagree. I consider it possible that if a speaker was connected between the red terminals of 2 different outputs that the voltage between them (and hence the current) could have been in excess of what the designer intended. I also think it possible that the protection circuit may not have seen that coming til it was too late.

Do you remember exactly what the wiring mistake you found was please? How do you think it was wired up?

I've picked up the 3802 receiver and don't want to take the risk of damaging it either, so it's a bit of a dilemma atm.

Is there a local decent home-cinema/hi-fi store with a workshop that could test them for you? I'd look for an independent store rather than a big chain if possible. I would ring one and say that I'd had an amp go bang on me and was worried that the speakers might be damaged. That way you're telling them these are potentially faulty and you're not tricking them into connecting them to a nice piece of new kit and damaging it. The workshop should have test amps for just this kind of situation. I wouldn't expect to be charged for a quick test. Even if they charge you $20 it's cheaper than a bad outcome. They may even be able to repair the amp too.

Cheers,
Paul.
 
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Paul Stimpson

Standard Member
Hi,

UPDATE:

I managed to find the circuit diagram for the AVR-1905 (which the page alleges is a close relative of the 2105) online. I would post the link but I'm not sure if that would offend against board rules. The board I suspect is the main board (page 6). I notice there are 2 fuses on it (marked F101 and F102). I would check that these haven't blown. It's quite possible that the amp won't power up if these fuses aren't intact.

Important safety note: Amplifiers of this quality have large capacitors that can store considerable amounts of electrical energy. These charges can cause serious injury or death. Do not open an amplifier unless you've unplugged it, given it time to discharge and understand the risks. Never connect an amplifier to the mains with the covers removed.

It's pretty safe to leave the amp unplugged over night, take both fuses out, (making sure you remember which is which), replace them with fuses of the same type and rating, put the cover back on and fire it up.

Cheers,
Paul.
 
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Moonlight

Standard Member
Hi Paul

Thanks for your continued assistance.

I had one of the front speakers wired around the wrong way into the receiver.

Also because I was using 2 subs, one of them lacked volume at the same volume level, so I probably had it turned up higher.
It was also turned up pretty high in the receiver under individual speaker levels.

As mentioned, when the music started, I remember the sound coming through the correctly wired speaker but not the incorrect one.

A couple of seconds later the very low sub bass from a keyboard started, and that's when I heard the rather loud 'pop' and the receiver went into protection mode.

The 'pop' was either going to be the protection kicking in, or blown circuitry.
The 2 subs were connected to a Y adaptor plugged into the single sub input.

I'm only guessing but as my fronts were set to 'large' and therefore receiving bass signal below 80hz, due to the wires being crossed, would this mean that the burst of bass signal had nowhere to go, and therefore caused something to blow?

I have tested the speakers on the cheapy receiver and they are working fine.
I am now testing the setup on my other better Onkyo receiver.
I'm going to try the one sub that was working fine first so that I can use the same setup on my 3802 receiver.
Then I will add the other sub connected to my F adaptor and not the Y one which was in use when it popped, just in case the wiring inside it was damaged.
If when trying both subs it pops my Onkyo receiver, I will know that the problem was not caused by the reversed polarity in the front speaker, but with the sub. The cable to it may be a bit dicey but this shouldn't cause any damage should it?....just not transfer the signal?

My mate believes that if the power works and there is sound coming through, even slight, then the problem must be elsewhere.

There is an electronics store locally so I will ask in there. There's also an HT specialist store in the next suburb, but I don't have a car.

ps. I sent this off as a reply before but don't know where it ended up?

pss. I avoid fiddling with electricals and prefer paying someone who knows what they're doing, if not, they fry and not me "D

Cheers
 
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Moonlight

Standard Member
Update - after some testing

Lounge mains

Cheapy Onkyo - connected each pr of speakers individually (no sub) …………….all worked
Good Onkyo - connected all cables except sub….heard a pop in a speaker….protection mode..no display
Good Onkyo - no connections………………………………………………………………………….display on
Denon - no connections………………………………………………………………………….protection mode..no display
Pioneer - no connections…………………………………………………………………………..display on

Study mains

Denon - no connections….protection mode…no display
Good Onkyo - no connections……………………………….display on
Pioneer - no connections……………………………….display on

Going back to try Good Onkyo in Lounge….connecting 1 pr speakers at a time
 

Paul Stimpson

Standard Member
Hi,

If all that was done was that the black wire was in the red terminal and the red wire in the black terminal of the correct output then that wouldn't cause any malfunction other than the system probably sounding crap.

You have multiple units showing strange symptoms. Are you sure your house wiring is OK? I'm wondering if a badly wired mains outlet/powerboard or a missing earth(ground) could cause these malfunctions. I've had a bad powerboard from the factory before.

Cheers,
Paul.
 
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Moonlight

Standard Member
Hi Paul

I was thinking that yesterday, as well as cables, but the Denon trips when just plugged in with no cables.

I had a double power point installed a couple of months ago, and asked about having a dedicated line from my HT to the mains board, as my vulcan heater fan on the other side of the room is connected to the same circuit and the fan switch is a bit dodgy.
He said that it may not make any difference.

I took the Denon to my bedroom setup and it still tripped when I plugged it in with no connections, however when I plugged the Pioneer that tripped in the lounge but was ok in the study, worked fine.

The old receiver and el cheapo speaker I used for testing in the lounge worked fine. I'm thinking these may not have the sensitivity of the others to detect faults.

I was thinking it may be the cable and have been flipping them around.
When trying a Jensen Centre, the sound was very low and scratchy, and when I held up the speaker wire, it tripped. Is it possible that a cable has been corrupted? This suggests to me that the contact was loose or barely enough to carry the signal, but isn't it a case of all or none?


I've been trying to make sure the wires are connected properly to the speaker terminals, but not 100% sure I have got it right?

The pop I heard initially may not have come from the Denon?
If there is no damage to it causing it to trip when display comes on with no connections, then it points to house wiring? But then why do the other receivers work?

It could be more than one cause?

I would turn the receiver ( Good Onkyo) on with fronts and centre, but when I turn my Topfield STB tuned to Jazz radio, it trips the receiver as soon as it runs.

Sheesh, this ones a mind bender but my tech mate tells me to be patient.:lesson:

ps. I did try using another powerboard, and also bypassing it and going direct.

I'll probably have to get a Sparky to come and test the power outlets?
 
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Paul Stimpson

Standard Member
Hi,

The thing about the Topfield really makes me think your earth (ground) could be defective. It could even be the earth for the whole house that has gone bad. Do you know anyone who is a qualified electrician that could go all round your house and do an "earth loop impedance test" on all the sockets? If there is a tool hire place near you then you could probably rent the tester. The ELI for my house is 0.3 ohms. If it was higher than 1.0 I would be worried. If it was higher than 3.0 I would be on the phone to an electrician on the spot.

Cables can break. You could have a fracture that makes contact because of the tension of the cable sheath holding the ends together but breaks contact when you bend that spot. You could also have a broken sheath that is OK when the cable is straight but when it bends the two conductors touch and short.

It is always possible that you have more than one fault. When this happens it's a real pain in the *** as you're looking for a single explanation for all your symptoms but there isn't one.

Do you have a test meter you could use to check the cable is good and doesn't go open or short if you work your way along it flexing? If you can find one that beeps when there is a connection (or a 9v battery and a buzzer) is really useful as you can play with the cable and listen for the noise.

Do you have a lump spare cheap cable you could use instead of the speaker cable to eliminate that?

Cheers,
Paul.
 

Moonlight

Standard Member
I do have a meter somewhere?

The Belkin Pure AV powerboards have a light for 'protected' and 'earthed' which are both still lit.
If there was a house wiring fault along that circuit, wouldn't these lights be out and the Belkin trip - and the 'reset' button pop up?


I'm still searching for the meter?

The first 2 speakers I connected (fronts) tripped the receiver, but after changing the cable with some new, the fronts were ok.
The centre cable has been replaced with cable from another setup which was working fine, but tripped the receiver.

I'm about to go through another round of trial and error??????

Regards :D

Edit: Previously turned receiver on first and then Topfield, and when Toppy kicked in, it tripped.
Thought maybe the burst of signal might be causing it? Tried turning on the STB and let it run, then the
amp…..yo….it didn't trip, sofar so good.
 
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Paul Stimpson

Standard Member
Hi,

Probably several...

The "earthed" light is an indication that the board thinks an earth is present. It's probably a very dumb device (a light that says there is a voltage present between the live and the ground wire.) If the ELI is high then it could still light, as would it if the neutral and ground were reversed. You could also have a bad neutral which could cause currents to flow in the earth. Does your home have any GFI/RCD/RCCD breakers (or whatever they are called where you live)? Is the circuit the hifi is on protected by one? Have you suffered any nuisance tripping of any such breaker? Have you had any "zaps" (small electric shocks) from touching metal items in your home?

Have you got a long mains cord you could run through the window to the neighbour's house? (or take all the hardware round there). If you eliminate the house power supply, does the problem go away?

Bear in mind that you may have a damaged amplifier so not all the problems may go away. If the symptoms change with a known-good power cord bringing mains from your neighbour's house then I would call a professional electrician at once. Ground/neutral faults can have safety implications.

Cheers,
Paul.
 

Moonlight

Standard Member
There is a circuit breaker on the mains board which has tripped a couple of times, once when the electric oven element broke a few months ago, and one other time about 5 months ago...could have been due to a dodgy toaster, can't remember, but it is certainly not a regular ocurance.
I've had a couple of zaps off the fridge handle ages ago but I figured that might have been due to being a bit charged up myself at the time?

The front and centre speakers were working until I lifted the cable. Fine on the fronts but tripped the receiver when I lifted the centre speaker cable. I must have broken the contact of the cable wire to the speaker terminal on the receiver which suggests I am not connecting the wire correctly to maintain contact. It's difficult toknow if you are getting good contact with those plastic terminal screws cause they don't unscrew completely to see if the wires are wrapped around the terminal.

I would prefer to avoid involving my neighbors as they are not 'personal friends'

Unless the Denon reverts to protection mode automatically when nothing is connected, it would appear that it has a fault?
I am waiting for a reply on that from Denon owners. The other two I have, Onkyo and Pioneer both show the display.
;)
 

Paul Stimpson

Standard Member
Hi,

Those trips sound like the breakers wee acting normally and it's definitely possible to zap yourself if you're charged with static and you touch something grounded. I'm not immediately alarmed by what you say.

Do the speaker terminals have holes drilled through them? The last amp I put in I remember stripping half an inch of the cable, pushing it sideways through a hole drilled in the post then screwing the plastic down over it. What does the manual say about that?

At the moment I'm tending towards the possibility that you have 2 faults. The Denon being in some way damaged and something else that's upsetting the Onkyo. I would be looking for anything that is common to both setups, so the speaker cable, mains and speakers would be at the top of my list to investigate.

Cheers,
Paul.
 

Moonlight

Standard Member
The terminals do have holes drilled in them.

Todays experiments were;
Changing the Belkin to another one that has been working ok - no difference there.
The tripping seems to be due to the centre speaker.
The Onkyo receiver has 2 impedance settings 4 ohms and 6 ohms. The Jensens are 4 ohms but as I don't think the Denon 3802 has a 4 ohm setting (as the manual recommends 6 - 16 ohm, I have been using the 6ohm so that the setup with the Onkyo can be transferred to the Denon when the bugs have been sorted.

Tried changing the cable and still tripped. My connections of the wires is better now on the receiver although the centre posts don't have much clearance from the back of the receiver metal casing. The next time I tried it using the Jensen centre speaker, it didn't trip but the sound was really scratchy whereas in the fronts it was clear.
I changed the centre to a cheap bookshelf - it tripped again and the second time it was scratchy as well.

Tomorrow I will try the Pioneer receiver which has those spring loaded clips for the speaker wires.
Trying this will eliminate the possibility of the wires arcing on the metal casing.

My impressions are…and only guessing...
I agree the Denon has been damaged.
My connections to the receiver have been dodgy but getting the hang of it now.
The cables could be corrupt but it is unlikely that all of the ones I've tried are?
The speakers are ok….unlikely that the Energy centre, Jensen and cheapy 'Dream' are all flawed?

I'm narrowing it down to my connections and cable at this stage. Using the pioneer tomorrow should eliminate the bad connection possibility, especially with the centre channel/speaker appearing to be one of..or the problem.

My downstairs and bedroom setups have not had a problem. It's only in the lounge, even when I bring receivers, speakers and cable into that setup that there is a problem.
The TV, STB, fronts all seem to be ok. If there was a problem with the mains or fluctuating, dirty power then the power would be interrupted and none of these would be working….and the powerboard would trip.

Well…that's my deduction sofar...with a good chance I may be barking up the wrong tree.

It would be handy to know which rooms are connected to the same circuit as the lounge.

Thanks for hanging in there with me Paul.
You obviously know a lot more about this stuff than me. It is a good idea to try the setup in someone elses' house to eliminate the mains as a suspect.
I'll keep looking for the meter

Cheers
 

Moonlight

Standard Member
Cracked it at last!!

Denon 3802 is up and running and no problems.

I'm not using one of the subs but the rest is working fine.
I used a good lead and tried it on it's own rather than into a splitter but it still lacked volume. Not to worry, the other one does the job for now until I get it checked out. Before I do that, I have ordered a new sub lead and will try it in another setup.

Ok….the problem was my connections to the receivers, both with the Pioneer and the Onkyo. The centre channel posts were underneath and I didn't see that the posts didn't have much clearance from the metal back of the receiver. In order to avoid getting the plastic insulation on the wire under the plastic screw-ins on the posts not clamping down the wires properly, I left it out too far, and this must have been arcing with the metal back plate on the receiver. I made sure the insulation was sufficiently in far enough to avoid this whilst having enough wire around the post to ensure good contact.

The problem with the Pioneer receiver was also a connection problem.
Different connections and I had not clamped the speaker wires correctly.

Wow..those 3802s are beasts.

Special thanks to Paul for lending a hand and seeing it through.

I guess my tech mate was on the money after all, saying it was my connections, start over again…and be patient.

The Denon 2105 appears damaged but may not be too serious.
I will send it in at some stage to be assessed and get a quote on repair for consideration.

Thanks AV forum….and again Paul Stimpson….:thumbsup:

This Denon 3802 ROCKS!!!
 
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Paul Stimpson

Standard Member
Hi,

Sorry for my absence. You're most welcome. I'm glad you got it sorted. :)

As far as the dead Denon goes I would put my money on a pair of popped transistors (about $50) or one or mode of the fuses on the main board having gone. The home cinema store in the next suburb may well be able to fix it cheaper than Denon will.

Cheers,
Paul.
 

Moonlight

Standard Member
Cheers Paul

I've just received back the Onkyo 574 that had been in for repair under warranty. It had a depressed tone button when I first purchased it and had distortion through one of the surround channels.

On the repair report it says;

'Dismantle unit, check for reported fault trace to 2 blown output transistors, and surrounding parts. Remove and replace faulty channel and repair tone button.'

Description Qty

Transistor 1
Transistor 1
Transistor 1
Transistor 1
Resistor 1
Resistor 4

Must have added up to a few $ (doesn't say)
Seems like the Tech was thorough which I'm glad about.
This authorized repairer covers different brands and said my Denon sounds like it would cost minimum $240 but likely to be more.

It's worth paying the $40 to check it and find out the cost of repair which I will do down the track.
If the Onkyo repair is any indication…..it may be expensive, but at least I would know that it would come back in top shape.
I'm guessing that because it is a warranty job, they would be more inclined to choose to replace parts to be on the safe side which would maximize their return?

I wonder whether it being a 'normal' repair, whether they would be as thorough?
Of course they would do whatever it takes to return the item totally fixed, and the only way to find out is to send it in.

I guess I'm the sorta guy that prefers to pay extra when I can afford it to get a good job done, although by purchasing items on eBay, I have been taking risks, and as a result I have been caught out a few times.
 

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