RF 200ix amp repair assistance

[mpednault]

I have a customer who has two old RF 200ix amps which both need repairs. He claims one of them he shorted the ground and power wires together and thinks he "blew a fuse inside". I'm not sure what's wrong with the other one. He's going to drop them off to me tomorrow and I'm going to take a look at them this weekend. I've never repaired an amp but have some limited experience in circuit board soldering. ie: I've hard modified Xbox's, built custom XO's for HT speakers, built various "things" using circuit boards and understand some of the terminology in electronics. I have a DMM and a nice soldering station to perform the repairs but that's it. I figured I'd at least crack them open to see what I find but wanted to post here to start the discussion and hopefully get some insight into what I'm potentially looking at for repairs.

[Perry Babin]

Read all of the basic amp repair page (link in sig line below). Read all of it, even the parts that you don't feel are important.

[mpednault]

Perry, thank you! that's an incredible resource you have put together. Invaluable! I shall dig deeply into the write up and hopefully come out with a repaired pair of amplifiers. Thanks again! If I have any more questions or need more assistance I'll post here and will also most likely post some detailed pictures of the failed components.

[mpednault]

Fixed one of the amps. It had a loose connection in the RCA inputs that I resoldered and it works fine now. So the other one I cracked open to find these 4 FET's FRIED! Should I just replace these 4 burned up one's with the same exact part (IRFZ44) or is there a better replacement? Is the IRFZ44N an equal usable equivalent? And should I just get the cheapest one's on ebay or look for a specific brand? Will I need to replace more than the 4 obvious broken ones? The rest of the board, devices and components look to be in excellent condition.

[AKHeathen]

don't order from ebay. there are a bunch of counterfeit parts floating around there. i order form digikey, but many use future, arrow, mouser, and some others i cannot remember. as far as i know, either irfz 44, or irfz44n should work. you are going to want to buy 10, to make sure they all come from the same batch, and replace the gate resistors as well. i would remove them, and power it up. take a voltage measurement to each of the gates and, if you can with your meter, hz and duty cycle, to make sure the fets are getting a good signal before installing. keep an eye on the voltage regulator(s), as they tend to get pretty hot, though i do not think they should be energized yet.

[mpednault]

Sorry for not digging for the schematic but where are the gate resistors on this board? I'm not very versed in amplifier electronics but if I'm pointed to which part(s) to replace I can easily desolder and solder in new... Since all the rest of the parts look great I'm goin to need a picture pointing out which resistors to replace on this specific amp. Thanks in advance for all your help.

I ordered ten of the IRFZ44Ns from digi.

[seankane]

They are the 4 surface mount resistors right next to the power supply fets. SMD package 0805 stock was probably 51 ohm.

I would replace the 4 driver transistors marked 1A and 2A as well they are by the TL494C PWM IC on the board.

Replace the following:

Q10, Q11, Q6, Q7, Q2, Q3, Q4, Q5, R36, R31, R32, R37

This should take care of the power supply as long as you dont have shorted rectifiers or transformer which is rare in this amp.

Make sure you dont have any shorted output fets before powering the amp though!!!

[KatieandDad]

Originally Posted by AKHeathen

don't order from ebay. there are a bunch of counterfeit parts floating around there. i order form digikey, but many use future, arrow, mouser, and some others i cannot remember. as far as i know, either irfz 44, or irfz44n should work. you are going to want to buy 10, to make sure they all come from the same batch, and replace the gate resistors as well. i would remove them, and power it up. take a voltage measurement to each of the gates and, if you can with your meter, hz and duty cycle, to make sure the fets are getting a good signal before installing. keep an eye on the voltage regulator(s), as they tend to get pretty hot, though i do not think they should be energized yet.

I've never had a problem ordering from E-Bay. Just be aware that there are some fraudsters out there. I've ordered components from recommended suppliers that have also been fakes.

[seankane]

I have ordered tons of parts from ebay with never any issues but only from reputable sellers. I recommend ACTIVEPARTS to anyone they have never did me wrong.

[motronix]

i dont know if this will help but the smd FET drivers is MMBT3904L & MMBT3906L
but i put the MMBTA06L & MMBTA56L [Rockford also put it in some models]

i have stock of Original Rockford Fosgate parts cuz i was the main service in my country. [sorry with my english :-) ]