JL Audio 250/1 blown output transistors

Brams96

Member
2013-02-25 1:11 am
Hi all,

I definitely found 1, possibly 2, output transistors (IRFZ44R's at Q300-Q305) that are faulty. One was a bit discoloured & the other was completely burnt out. I was going to replace them with IRF3205's as they are 2X the current rating.
The problem I have is some of the SMD resistors in front of them are all burnt out too & I need to know what value they are.

Can anyone help with what value they are or know where I can download a schematic diagram??

Thanks in advance
 

Brams96

Member
2013-02-25 1:11 am
Ahh, my bad I thought they were the output transistors. I'll get on & order some more resistors now, I might as well replace all 6 while I've got it in bits. I will use my multi meter tonight to determin if anything else has blown or is suspect. Thanks very much for the help, I'll let you know how I get on ;)
 

Brams96

Member
2013-02-25 1:11 am
Well I tested all the z44r's & the other 4 still on the board are ok, as are the drivers for them all. All 6 SMD resistors will need replacing as 2 were missing/blown up & then the other 4 pretty much fell off when I touched them. The board around the blown z44 is a discoloured brown colour like the resin got quite hot & it even stained the aluminium heat sink too. The 540's are ok as well.
On a different note I managed to fix a Vibe A0 amp that wasn't working either. The cap for the power (1000uf 25V) had burst the top & leaked so I replaced it with a 35V spare I had & hey-presto! Fixed.