# Hifonics BRX5016.5 repair



## kritiostodd (Feb 1, 2009)

I've had this amp installed for about 2 months. The other day, I power up my head unit, hear a little pop, and smell a little electrical burning odor. No more bass coming from the sub. The other channels appear to be working ok. 

I pulled it out of the truck and opened it up to see what I could find. I bought it (barely) used so I'm not worried about a warranty repair. Looks like one location is affected. Is the fix as simple as removing these two components and soldering in new ones?


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## bnae38 (Oct 3, 2015)

Guessing those are on power supply side, not the output devices?

Usually change all the fets with a new matched set with parts from a reliable source, i.e. digikey etc. There is also a chance the smaller buffer transistors used to drive them have gone bad too. Also need to check for blown gate redistors.. r249 and 252 likely in bad shape.


If you pull the board, ohm out the output devices too, look for any unusually low resistance between any of the 3 legs.


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## kritiostodd (Feb 1, 2009)

Thanks. I’m a total beginner so it looks like I’ll need to do some research. 


Sent from my iPhone using Tapatalk


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## bnae38 (Oct 3, 2015)

No worries.

https://www.digikey.com/product-detail/en/infineon-technologies/IRF3205PBF/IRF3205PBF-ND/812033

https://www.digikey.com/product-detail/en/stackpole-electronics-inc/RNMF14FTC47R0/S47CACT-ND/2617508

Might be 1/8w resistors but anyway. Should get you started.


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## bnae38 (Oct 3, 2015)

Don't forget to replace that insulator too if you dive in.

Looks burnt to a crisp, if the fets electrically come in contact with heatsink= bad news.

Kapton tape works fine. Also need thermal paste.. adds up quick


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## TheSteve (Jun 15, 2018)

i second the resistor statement
you can see the 2 on that pair are toast (compared to the set next to them)
also note the shrink tubing on the legs (uncommon, but will need to be installed on the new parts)
because the resistors are burnt odds are the drive transistors are gone as well
best way to tell is with a scope on the gate pins to compare with other sets

often using a small supply (under 5A) on the bench you can actually clip out the bad parts and power up for wave testing


PS this unit appears to have 2 power supply transformers with 4 FETs pushing each
you should replace all the fets on the effected transformer, but leave the other ones alone

keep the FETs you remove as they likely match the other set you didnt change and can be used to replace just failed ones on that side if needed later

often with bad drive transistors it will run on the bench and die in the car, so be sure to check for even heat and matching waves after repair


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## kritiostodd (Feb 1, 2009)

Thanks for all the input! I’m a complete novice at this part of the hobby so I really appreciate the help. Looks like I have a few more supplies to order or find locally, then try to give it a go.


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## TheSteve (Jun 15, 2018)

wow 110A rated FETs
those may be a hard find










nope was easy to find the IRF3205 matches the specs


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