# Alpine MRV - M500



## T0mer (11 mo ago)

Hello all,
I have a alpine amp where i would like to replace 4 of the transistors on one bank. The existing look to be labeled

IRF 3205
I$R 545p
1A 82 

i have called alpine - who were of no help identifying or selling the parts. I also called Mouser...however they said it could be any number of 3205s. ( i would need to identify the ohms). Would anyone know the OEM transistor's impedances? Any help would be much appreciated. (Incidentally the amp was damaged when i was in a rush to install this used amp to test it before buying and mistakenly reversed pos/neg terminals....(the fuses, i think, would have blown except i later found out that the previous owner jumped the fuses instead of replacing them.)


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## dkc7 (Jan 7, 2022)

Ouch


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## cman (Aug 24, 2020)

Digi-Key has them in stock… just buy the same part number. These are mosfets and you want to replace all of them at the same time from the same batch.


you can put one or two in to test functionality, verify it doesn’t blow up again… and then replace the rest with matching once you check that. but being how cheap they are I would replace all in the amp that are that part # and try it


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## T0mer (11 mo ago)

cman said:


> Digi-Key has them in stock… just buy the same part number. These are mosfets and you want to replace all of them at the same time from the same batch.
> 
> 
> you can put one or two in to test functionality, verify it doesn’t blow up again… and then replace the rest with matching once you check that. but being how cheap they are I would replace all in the amp that are that part # and try it
> ...





cman said:


> Digi-Key has them in stock… just buy the same part number. These are mosfets and you want to replace all of them at the same time from the same batch.
> 
> 
> you can put one or two in to test functionality, verify it doesn’t blow up again… and then replace the rest with matching once you check that. but being how cheap they are I would replace all in the amp that are that part # and try it
> ...


Cman- thanks for the replay. I was indeed preparing to replace them all. Suppliers have them...there are just different options of ohm ratings. Mouser mentioned they have either 8 ohm or 6 ohm to choose. I unfortunately dont know the ohm rating... or how to find it. The mouser rep mentioned that if i select wrong it can either cause the amp to not power up...or damage other internal parts. If someone can confirm the ohm rating i should use, i can move on them. 
Thanks


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## T0mer (11 mo ago)

T0mer said:


> Cman- thanks for the replay. I was indeed preparing to replace them all. Suppliers have them...there are just different options of ohm ratings. Mouser mentioned they have either 8 ohm or 6 ohm to choose. I unfortunately dont know the ohm rating... or how to find it. The mouser rep mentioned that if i select wrong it can either cause the amp to not power up...or damage other internal parts. If someone can confirm the ohm rating i should use, i can move on them.
> Thanks



@cman....just saw your followup message, thanks again


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## cman (Aug 24, 2020)

Looks like a regular old IRF3205 (non Z and non AU) to me... I honestly could not say for sure as i am by no means an expert on chip markings.. but from google research it appears the Z variants are the 6.5 ohm.. and then there are also auto grade ones that start with "AU"

This below is what it appears to be (to me at least)












It appears that the 6.5 ohm version .. has a "Z" added to the part# IRF3205*Z*. I do not believe yours is 6.5ohm since the chip says IRF3205 not IRF3205Z

also there is an AU automotive version.. which this is NOT. The mosfet would say "AUIRF" if it was automotive.. or it was Z variant (6.5 ohm) it should say "IRF3205Z"

Like I said, i cant say for 100% certainty, sometimes markings on chips are weird and leave out certain letters... but from my research it appears the Z variants say IRF3205Z... not just IRF3205 like yours does.


I would also check this out..






AUIRF3205 versus IRF3205 for Alpine MRV-F540


I've got an Alpine MRV-F540 that was losing one channel so I set it aside for a few years and just now pulled it out to try to figure it out and learn more about amps. There are four IRF3205 FETS mounted in one corner that have been getting very hot, and one in particular is really nasty...




www.diyaudio.com


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## cman (Aug 24, 2020)

Good luck, if you need more help I would join the facebook group "DIY Audio"- There are alot of guys in there that modify or build amps.. alot of crazy stupid info (per usual on the internet) but also alot of very smart people who will give you great information if you make a post.


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