plate amp dead?

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yappari
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Postby yappari » Thu Jul 13, 2006 9:23 pm

sorry it took so long, here are the pics :)

Image

Image
----------------------------------
US Amps 200
->Ascendant Avalanche 15"
->4.8cuft box tuned to 36hz
US Amps 150
->CDT CL-61
Pioneer 6700mp
-> MTX RTX03A
->AudioControl EQL
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eezip
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Postby eezip » Thu Jul 13, 2006 10:16 pm

First, it's a transformer, not a tolenoid. There's no such thing.

Sometimes there are fuses inside transformers, many times there are fuses on the PCB - as you stated, yours is 1.6A. You said the fuse blew later when smoke came out - did it blow at first also?

Transformers often fail without any externally visible signs. They have so much mass and failures usually occur at the center. Failure of transformers is msot likely due to heat which can cause fires but usually just damages the transformer internally.

Since you're the one there you're going to have to help us out:
1. You said smoke came out - where did it come out of and did it continue after the fuse blew?
2. As westend said, take a picture of both sides of the board.
3. The next things to check will be the transformer, bridge rectifier, and output devices.
4. You'll want to unsolder the transformer leads from the PCB and measure the AC voltage from yellow to each red lead. Be careful as you'll be dealing with lethal voltages - it's best to have 2 people.
5. The bridge can be checked using the diode test on most DMMs. It's the black square right next to where the transformer secondaries enter the PCB. Check all 4 diodes both in the diode test and resistance - it could measure ok but still be leaky.
6. You will need to take the aluminum stock off the power devices if there are no visible clues on the exposed parts as to what happened. If you're not comfortable with that, get help or take the amp to someone experienced. Search online for the type of output devices and then test them accordingly. If you post or take a picture of the devices we can tall you how to test them.
HT: Sony KV-27FS13 | Oppo DV-981HD | Denon AVR-2807 | 7x Cambridge MC100 | Acoustic Research ARPR1010 || Stereo: Dynaudio Audience 42 | Hales Concept 3 prototypes | wouldn't you like to know... :)

Home PC: Yamaha RP-U100 | B&W LM-1 | Mpyre 65x || Work PC: Yamaha RP-U100 | QSC AD-S32T | Sony MDR-V600
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westend
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Postby westend » Fri Jul 14, 2006 4:04 am

From the pics it looks like you have melted the mosfets onto the heatsink and the one by that smoke stained resistor is gone. At the very least you will need to replace the Mosfets and I'd be very surprised if there are not other issues. Is there a schematic diagram anywhere on that amp case?
Pioneer 860, Soundstream 600-4, Directed 1100d, CDT IEK, CDT EF61CF, 2-IDQ-10's NoGOT-No gas on Thurs.




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eezip
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Postby eezip » Fri Jul 14, 2006 10:23 am

westend, possible, but I think the 'goo' or whatever it is on the heatsink is some kind of TIM. The fuse would blow [and it did] before a catastrphic fault could have melted the epoxy of the output devices. Fuses blow before things can get hot enough to melt like this - the epoxy will crack apart under magnificent stresses and then the fuse will go. Anything is possible, but I've seen some spectacular failures during abnormal UL testing and the like and never seen this. This is why I said we needed to see the outputs next because we don't really know what's going on.

Darkened resistors are common with high power types. This happens under normal operation. It's very true that this can be a sign of failure or stress to the resistor, but it can also be normal if the resistor is dissipating power near it's limit [but still safe power levels] over time.

By the way, don't just to the conclusion that the output devices are FETs. I see that a lot around here and I use the term output devices because they could be FETs or bipolar transistors.
HT: Sony KV-27FS13 | Oppo DV-981HD | Denon AVR-2807 | 7x Cambridge MC100 | Acoustic Research ARPR1010 || Stereo: Dynaudio Audience 42 | Hales Concept 3 prototypes | wouldn't you like to know... :)



Home PC: Yamaha RP-U100 | B&W LM-1 | Mpyre 65x || Work PC: Yamaha RP-U100 | QSC AD-S32T | Sony MDR-V600
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yappari
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Postby yappari » Sat Jul 15, 2006 12:28 am

yea the goo is a TIM, it like that before, the resister just has a gray shadow behind it from teh camera, but its looks like new. i'm not an engineer or anything, but i've modded plenty of playstations, occationaly worked on a hobby project that required working on pcb, so i have some experiance with finding burned stuff on pcbs (cheap modchips are a bad idea), this is a really small pcb and i've looked at it plenty of time everything on the board should be okey (except the chips and the pots, they might be set wrong)

i'm pretty sure thats a toleniod, if i look on the label it says toleniod, i looked them up on ebay and found them for sale (might be a good idea if it really is blown)
the fuse that blew was the one on the pcb, i'm starting to think that the smoke came from it because its all black and not very well sealed. its kind of scary because its a slow melt fuse which means that it was taking a serious amount of power.
as far as heat, i think that might have been the issue, before this happened the aluminum block over the mosfets looked normal, but now its discolored and slightly warpped (sounds like a lot of heat in one area). my uncle tells me that in between each layer of coil on the toleniod theres a plastic cover, he thinks a layer might have melted and it might be shorting. i think this might be also what caused the tone because it might have made a strong EMF (if i ever had a cellphone or an application that generated an emf close to the sub amp, you could hear loud noise from the sub)
i donno.. maybe i'm talking out of my ***, but its just a guess, i need to find out how to see if the toleniod is in working order
----------------------------------
US Amps 200
->Ascendant Avalanche 15"
->4.8cuft box tuned to 36hz
US Amps 150
->CDT CL-61
Pioneer 6700mp
-> MTX RTX03A
->AudioControl EQL
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eezip
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Postby eezip » Sat Jul 15, 2006 3:10 am

First, that is definitely a transformer. Not a tolenoid. I don't care what the label says. Trust me like Jasmine did Aladdin.

Also, as I posted earlier, the outputs may not be FETs.

Check the fuse and see if it's a short or open.

Unsolder the transformer secondary from the PCB and plug the cord into an outlet. Get ready to pull the plug in case the transormer windings are shorted and I suggest using a power strip that has a breaker. The AC voltage should be the same from yellow to each red wire.

The wire around the core of a linear transformer is covered in enamel [sometimes other materials but not for something cheap and mass market] and then dipped in epoxy or resin to hold it all together once it's all wound. This can short but it takes a hell of a lot of heat and it's unlikely a failure that pulled enough current to blow the fuse would allow enough heat to build up to damage a transformer. A fuse usually blows during catastrophic failures whereas a transformer overheating is a slow process because there's so much thermal mass.

But let's not jump to conclusions since we don't know the problem. Strange and amazing things do happen but if you check the things I listed above we can start making progress towards what's really wrong here. :)
HT: Sony KV-27FS13 | Oppo DV-981HD | Denon AVR-2807 | 7x Cambridge MC100 | Acoustic Research ARPR1010 || Stereo: Dynaudio Audience 42 | Hales Concept 3 prototypes | wouldn't you like to know... :)



Home PC: Yamaha RP-U100 | B&W LM-1 | Mpyre 65x || Work PC: Yamaha RP-U100 | QSC AD-S32T | Sony MDR-V600
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westend
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Postby westend » Sat Jul 15, 2006 3:44 am

Thanks for straightening me out on FET's, EE. My eyes are getting as old as me. I couldn't make out if that was a sealant or melted plastic but when I looked at the line of the output devices it seemed that one was gone on the left side. Probably camera angle or some such.
To the OP, you have a very experienced amplifier guru with EEzip. This is not some kid who rewired his speaker outputs, once. If he says that is a picture of a torroidal transformer and not a tolenoid, I'd give him the benefit of the doubt.
BTW, if the repair job doesn't work out for you I have a Dayton 250w. plate amp I could part with as I'm not using it. Somebody shot me a great deal on a bigger pro amp.:cwm18:
Pioneer 860, Soundstream 600-4, Directed 1100d, CDT IEK, CDT EF61CF, 2-IDQ-10's NoGOT-No gas on Thurs.




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Dracula McNeill
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Postby Dracula McNeill » Wed Jul 19, 2006 1:52 pm

My buddy fried his amp an that's just the ***** of it, there could be any number of things wrong in there. Only thing to do is open her up and show all your friends and hopefully someone will be able to pick something out...
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eezip
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Postby eezip » Thu Jul 20, 2006 10:16 am

yappari, have you had the opportunity to check anything out in my post? I'd like to help you get this amp going again. A shot straight down [perpendicular to PCB] on both the top and bottom would be the most informative for me about where things are located.

Westend, FETs, bipolars ... I'm just throwing things out there :) thanks for the kind words :cwm28: :D
HT: Sony KV-27FS13 | Oppo DV-981HD | Denon AVR-2807 | 7x Cambridge MC100 | Acoustic Research ARPR1010 || Stereo: Dynaudio Audience 42 | Hales Concept 3 prototypes | wouldn't you like to know... :)



Home PC: Yamaha RP-U100 | B&W LM-1 | Mpyre 65x || Work PC: Yamaha RP-U100 | QSC AD-S32T | Sony MDR-V600

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