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Plate amp repair question
Plate amp repair question
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Old 11th January 2019, 05:18 PM   #1
Bret burrill is online now Bret burrill  United States
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Default Plate amp repair question

Pioneer sw8-mk2. This my first time attempting a repair on a board. Before you tell me this amp isn't worth the effort, let me say my goal is to learn to repair stuff and if I end up with a usable amp that will be a bonus.

Visual inspection - fuse blown and one component is separated from the plate where a conductive grease had been applied. I see a hole in the plate next to the component, was there once a screw or clamp there perhaps?

I assume I don't want to put a new fuse in and plug it in.

The component has three legs. I don't know what tests to perform. I checked and there is continuity between the outer legs, but without even knowing what the component is, it means nothing to me.
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Old 11th January 2019, 08:03 PM   #2
Bret burrill is online now Bret burrill  United States
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Made a makeshift clamp. Still blows fuses.
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Old 11th January 2019, 08:11 PM   #3
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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The tab on the transistor must be electrically isolated from the heat sink as the heat sink is normally ground and the collector of the transistor could be anything.
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Old 11th January 2019, 08:12 PM   #4
llwhtt is offline llwhtt  United States
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The semi-translucent material between the transistor and the chassis is a mica insulator. By installing that screw like you did you defeated the whole purpose of the insulator. There needs to be a nylon shoulder washer between the head of the screw and the transistor. Without screw installed and it still blows the fuse you have bigger problems than a missing screw.

Craig

Jon beat me to it.
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Old 11th January 2019, 08:14 PM   #5
Bret burrill is online now Bret burrill  United States
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OK thanks. There is a thin piece of material under the transistor that must be there to isolate it. Ill redo the clamp so it doesn't short the thing out.
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Old 11th January 2019, 08:19 PM   #6
llwhtt is offline llwhtt  United States
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You can leave the screw out for now, if it still blows the fuse either that transistor? is bad or you have other problems. Do you have any test equipment? Are there any numbers on the part?

Craig
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Old 11th January 2019, 08:44 PM   #7
Bret burrill is online now Bret burrill  United States
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I didn't see the replys until after I made a clamp. There are numbers but I have to buy a loop to see them. I'll go get one and post the numbers in a bit. Thanks for your help.

Looking at the pic it looks like the mica slid and the tab might be making contact. I'll check that. There is nylon around the screw so it is not touching the tab.
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Last edited by Bret burrill; 11th January 2019 at 08:47 PM. Reason: details
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Old 11th January 2019, 10:20 PM   #8
Bret burrill is online now Bret burrill  United States
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irf9530
y37k
a0

here is a link to the datasheet: http://www.irf.com/product-info/data...ta/irf9530.pdf

I'll see if I can figure out how to test it with my multimeter

If it was running unclamped it wouldn't take long to cook it I suppose.

Last edited by Bret burrill; 11th January 2019 at 10:26 PM. Reason: Add link
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Old 11th January 2019, 11:08 PM   #9
llwhtt is offline llwhtt  United States
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OK those are MOSFETS, looking at the face with the pins towards you, pin1 is on the left and pin 3 is on the right. Pin 1 is the Gate, Pin 2 is the Drain, and Pin 3 is the Source. You should have no continuity between Pins 2 and 3, if it reads ZERO it's shorted. Yes if the amp was run for any length of time they are probably fried. Make sure you check the other one also and always replace in pairs.
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Old 11th January 2019, 11:10 PM   #10
Bret burrill is online now Bret burrill  United States
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OK thank you. Do I need to detach them from the board in order to test them?

I tested it still attached to the board and there is continuity between 2 and 3

Last edited by Bret burrill; 11th January 2019 at 11:14 PM. Reason: tested
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