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
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
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.
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.
http://www.bcae1.com/temp/rockford - punch40i-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.
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.
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.
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.
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.
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.
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.
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.
Well this is strange, the dead channel started working when I was testing it !?! All seems fine now but a resistor next to the transformer is getting quite warm - I'm wondering if this is OK?
Here's what happened:
I measured the DC on the speaker terminals and it was zero (I also measured the RCAs (for some reason) and they were 1v on the dead channel and 1.9v on the good channel).
So then I thought maybe I ought to test for DC output with an RCA signal going in, so I put some music into it from the HU rear channel and I had a speaker connected directly to the HU front channel just so I could monitor what was going in - when I plugged in the RCA this time the front speaker carried on working (previously everything went quiet - front and rear left and right).
So I connected everything up and it worked fine.
Then I disconnected and tested for DC again. Still nothing on the speaker outputs and now nothing on the RCAs either (well actually, I did just find a very slight reading like 0.05v on one side).
Then I let it run and checked to see if anything was getting warm, I didn't have time to run it for long but the transistors and their resistors all seem to be behaving themselves.
The only thing I found getting hot is a 10 ohm resistor sitting just on the output side of the power transformer (R35). In the diagram for the Punch 40 there are two of these (R35 and R36) and both are shown as 22 ohm, my 60ix just has one and it's 10 ohm.
It's not getting like really hot - I can just about stand to keep my finger on it, so I guess it's probably approaching 50 *C. I don't know whether that's normal. Maybe I should check what current the amp. is drawing at idle should I ?
Here's what happened:
I measured the DC on the speaker terminals and it was zero (I also measured the RCAs (for some reason) and they were 1v on the dead channel and 1.9v on the good channel).
So then I thought maybe I ought to test for DC output with an RCA signal going in, so I put some music into it from the HU rear channel and I had a speaker connected directly to the HU front channel just so I could monitor what was going in - when I plugged in the RCA this time the front speaker carried on working (previously everything went quiet - front and rear left and right).
So I connected everything up and it worked fine.
Then I disconnected and tested for DC again. Still nothing on the speaker outputs and now nothing on the RCAs either (well actually, I did just find a very slight reading like 0.05v on one side).
Then I let it run and checked to see if anything was getting warm, I didn't have time to run it for long but the transistors and their resistors all seem to be behaving themselves.
The only thing I found getting hot is a 10 ohm resistor sitting just on the output side of the power transformer (R35). In the diagram for the Punch 40 there are two of these (R35 and R36) and both are shown as 22 ohm, my 60ix just has one and it's 10 ohm.
It's not getting like really hot - I can just about stand to keep my finger on it, so I guess it's probably approaching 50 *C. I don't know whether that's normal. Maybe I should check what current the amp. is drawing at idle should I ?
[Edit - thanks Perry, you posted while I was adding a post myself - I'll just use it for a while and keep an eye on it then]
In case it's of relevance or interest the place I got my parts from suggested IRFZ44VPBF as a sub for IRF44N and IRF34NPBF as a sub for BUZ11.
I got some of each and I used IRFZ44VPBFs on the power supply. The resistors are 68 ohms.
In case it's of relevance or interest the place I got my parts from suggested IRFZ44VPBF as a sub for IRF44N and IRF34NPBF as a sub for BUZ11.
I got some of each and I used IRFZ44VPBFs on the power supply. The resistors are 68 ohms.
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