diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Car Audio (http://www.diyaudio.com/forums/car-audio/)
-   -   Rockford Fosgate 60ix FETs blown (http://www.diyaudio.com/forums/car-audio/190895-rockford-fosgate-60ix-fets-blown.html)

LazySteve 15th June 2011 03:17 PM

Rockford Fosgate 60ix FETs blown
 
Hi I'm new here, can I say first of all how much help I have already got just from searching around this forum which is excellent, and I think I have got this mostly sussed out already, I just want to check a couple of things if anyone is kind enough to be able to help.

So, I have a Punch 60ix with power supply failure. It draws 100mA from a 12v source but that's it. There are two gate FETs which are IRFZ40s and which test as shorted (and there is some blackening around them). Also I can see what I believe are the two gate drive resistors associated with these FETs and they have gone open circuit (and they look like they got a bit hot).

The rest of the board looks nice and clean (sorry no pictures at the moment, unfortunately I am typing this from work without the board in front of me).

I can get replacements for these four blown components but I would like to order all the parts I am likely to need in one go. I have seen on here to check the driver transistors for the power supply FETs and the large Zener diodes near the FETs. I think I can identify the zener diodes as the two little bead shaped fellas near the transformer, but I'm not sure which are the drive transistors. I assume they will be assigned a "Q#" number on the board.

I am wondering whether I should test anything else or just change any of the above which tests bad and connect the power (I have noted that I will need to connect with a suitable fuse in circuit).

Also, are there any tricks for removing/replacing the FETs vis a vis the heatsink?

Thanks in advance

Steve

Perry Babin 15th June 2011 06:11 PM

What's the PC-# on the circuit board?

LazySteve 16th June 2011 11:15 AM

Hi Perry, for some reason I didn't get a thread reply notification?

Anyway, the number is PC-0764-F

The burnt resistor numbers are R31 and ??2, I think R32 but hard to read due to the blackening.

I'm a bit confused because I downloaded a circuit diagram which says it is for a 60ix but there are four power supply FETs shown on the diagram (Q6, Q7, Q10 & Q11) and my amp only seems to have two (Q6 & Q7) ??

Another odd thing I noticed is one of the little allen screws which hold the board in has got its head missing. I can only think it was over tightened in the factory because both of the warranty stickers were intact before I opened up the amp.

Perry Babin 16th June 2011 04:11 PM

http://www.bcae1.com/temp/rockford%2...h40i-topaz.pdf

This ^ should be close to what you have. If it's not, you can get the correct diagram from Rockford. The drivers are Q2, 3, 4 and Q5 on the diagram.

LazySteve 16th June 2011 09:00 PM

Thanks Perry, unlike the one I found on the net that diagram actually looks like my amp. !

Re: my original post, should I test anything else before trying power up - or just change any of the components I already listed and which test bad?

Also can I just share this - I didn't know this amp was bad when I bought it but in a funny sort of way I'm now actually pleased that it was broke because it means I can maybe save it. I know that doesn't make sense but somehow it just seems right.

Perry Babin 16th June 2011 09:20 PM

You should check the output transistors to confirm that none are shorted.

After replacing all of the defective parts, clamp all transistors tightly to the heatsink and insert a 10 amp fuse in the B+ line. This will help protect the newly replaced components if there is another problem.

While the power supply FETs are out of the circuit, confirm that the resistance between the B+ and ground terminals is well above 0 ohms. The meter should increase in resistance as the filter caps charge.

LazySteve 16th June 2011 10:22 PM

Message received and understood.

It will probably take me a few days to get the parts and work through this and then I'll report back.

I can't thank you enough.

LazySteve 22nd June 2011 09:16 PM

Well, it's working :cheers:

But only on one channel :(

Hey it does sound pretty good though !!

So now I just need to investigate the bad channel - I guess it helps the diagnosis with one good channel for comparison.

Thanks again.

LazySteve 22nd June 2011 10:26 PM

Hmmmm...... I can't find anything wrong. I already checked the output transistors before, but I checked them again and they seem OK. The resistors associated with them all seem OK (though my meter's lowest range is 200 ohms so not too accurate at reading around 1 ohm level).

A couple of things that I'm sure are clues to what is wrong are these:

1) if this channel is connected and I turn on the HU I get a bump from the speaker, so something is happening;

2) if I have everything else except this channel connected (I'm only testing with a low signal input) then plugging in the RCA feed to this channel shuts everything off; like it's making a short on the output, though I can't measure any difference between the channels input or output.

Anyway it's half past eleven here so I think I'll give it a rest for tonight.

Perry Babin 23rd June 2011 12:39 AM

With no speaker connected to the dead channel, what is the DC voltage measured directly across the terminals for the dead channel?


All times are GMT. The time now is 07:02 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2