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Old 1st November 2013, 08:29 AM   #1
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Default Alpine mrv-f545 repair

hi everyone I just signed up and thought ide start sharing my repair work so that hopefully others may get some useful information from it, I'm only learning my self and I feel ide give something back for all I've learnt from others on here, so to start with I have a Alpine mrv-f545 with blown fuses and oc on the display before it blows fuses,, I've already played a bit with this amp so I'll try to get pics and my progress up next, thanks
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Old 1st November 2013, 08:59 AM   #2
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can anyone start by telling me if these power supply fet,s are suppose to be the same or similar? I replaced the left with the right and they seem to be overheating straight away.
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Old 1st November 2013, 09:24 AM   #3
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Same type number, different production codes... so yes the same.

Failure or overheating of output devices is usually a sign of a problem elsewhere such as drive issue.
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Old 1st November 2013, 10:02 AM   #4
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ok well this is what I thought, production code, but I've got a data sheet on the fkv-550 t and fkv-550 n and the difference is something in the gate voltage, I'm wondering if the t and the n are actually different part numbers and therefore I'm getting some overlap somehow in the power supply, its strange because the t is rated lower gate voltage. and the reason I say all of this is yes the amp has dual power supplys , it has 4 fkv,s per supply, but I still have 4 good fkv550n,s and if I power the amp up with just those 4 it powers up one power supply fine, +37 -37v but then I can take those 4 out put 4 of the fkv550t,s in and as soon as they start switching they start burning up and the voltage starts drooping, the gate voltage is fine at 5.20v at 26hz I think, and I know the fkv550t,s are good because I just put them back into the kenwood amp they came from and it works, next in going to measure the gate voltage in the kenwood, maybe they are pro codes but they came from the factory with slightly different carachteristics so they had to make a different data sheet? I'm not sure on this one all I know is I have a fkv550t and fkv550n datasheet and they different, and I never would have thought the t or n down where its printed would be anything to do with the data, ill post the outputs too because there is numbers on the bottom of them and the funny bit is the ones with the other numbers run the lower power ch 1,2 on the amp, which has 4 output transistors compared to the 3,4 channel which has 8
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Old 1st November 2013, 10:11 AM   #5
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Have to admit that that does point to a difference... if if it works OK with one variant and not the other.

You need to look at the actual gate drive voltage available from whatever drives these FET's and compare with the data sheet. Look to see at what Vgs the device is guaranteed to be fully conducting and see how that compares to the data sheets. If the gate drive is insufficient to fully turn on the FET's then will be operating partly in a linear mode and that would explain the heat generation.
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Old 1st November 2013, 10:14 AM   #6
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here are the outputs, notice the 4n p and 40 y on the bottom, there is 2 a,s and 2 c,s with one number for the small channels and 4 and 4 of the other for the other larger 2 channels, these ones might be nothing but I just want make sure before I replace the one blown one
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Old 1st November 2013, 10:21 AM   #7
Mooly is offline Mooly  United Kingdom
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They might refer to gain groups (hfe range) but whether its of importance I wouldn't like to say. For devices that are in parallel matching helps ensure current sharing etween devices.
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Old 1st November 2013, 10:25 AM   #8
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this is what I found on the t and n, just never realised that down in the right bottom corner that a t,or n, had anything to do with anything besides a date or code, so maybe its something we can learn if I am correct.
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Old 1st November 2013, 10:28 AM   #9
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I'm thinking probably the same with the outputs, even though both are full range outputs, one is bridgable and more than likely is going to be used as a sub channel, I'm still learning some basics so excuse me if I ask or say something noobish,
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Old 1st November 2013, 10:31 AM   #10
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That shows the T version will operate in saturated mode with a much lower gate drive voltage than the N version. Looks as though that is the reason for the overheating. I'm guessing the drive voltage is from 5 volt logic for that to happen.
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