Crossfire VR2000D Repair issues

[intensem1rider]

I was referred here by "I am an Idiot" from another forum to ask for help about my amplifier repair.

I'll start from the beginning:
The amp sat in my garage over winter and this summer I went to install it and when the fuse was connected the amplifier shorted out and shorted some of the transistors on one side of the out put stage of the amp, and a few emitter resistors and a collector resistor went, I replaced all the parts with the exact replacements of the same specs or of higher tollerance. Upon powering the amp back up I was only able to achieve up to 7 volts of output which was very distorted. I then removed all the transistors on the one side of the output bank and powered it up thinking if just one side of the board has an issue, then at least I should be able to achieve at least 30 volts on the outputs, but with a signal being sent to the amp it goes into protect before 3 volts is achieved and there is some rectangular blue plastic incased capacitors mounted in the center of the board between the power supply side of the board and the output side of the board that are clicking internally like a relay that is bouncing back and forth. First I removed the one that was clicking and powered it up again and then another one would click, then I would remove that one also, then another one would click until all of them were removed.
I was advised to look for dust on the coils but did not see any, or any sign of shorting period. I am really quite stumped.

Some pictures of the amp can be available here for reference.
http://intensem1rider.tripod.com/jayzpicpage/

Thanks
I appreciate any help.
Family ordered me the BCAE amp repair dvd for Christmas and am patiently waiting on that to possibly try to figure that stuff out myself.

[Perry Babin]

When you receive the DVD, look at the page named 'generic class D - type 1'. It has information on amps using this type of audio circuit (used by JBL, Memphis, Kicker...).

We need to determine if the problem is in the audio section or in the power supply section.

There are photos with transistors installed and transistors missing. Which transistors do you have in the board at this time?

Are any of the transistors heating up when you power up the amp?

If you measure the resistance across the blue capacitors (out of the board), do they read as open?

When you power it up, what is the DC voltage on the third leg (source) of the IRFB31N20Ds?

What is the voltage on the third leg of the IRF9640s?

Place the black meter lead on the secondary center-tap of the transformer (just left of the body of R761) when measuring the voltage on the third leg of the transistors.

What is the DC voltage across the following diodes? These are the orange diodes on the driver board.
D271
D272
D471
D472

Did you replace any of the transistors on the audio driver board?

Can you take a photo of the bottom of the driver board? Zoom in so that you only capture ~1/3 of the driver board in the full frame. All I need to see is from Q981 to the edge of the board. Since you can't post high res images here, email it to me or post it on the tripod site.
babin_perry@yahoo.com

[intensem1rider]

There are photos with transistors installed and transistors missing. Which transistors do you have in the board at this time?

((I have the transistors on one side of the board removed, these were from the side where there were a few shorted originally, 0241, 0214, 0213, 0212, 0211, 0341, 0314, 0313, 0312, 0311) In one of the pictures I posted, the transistors that were bent up were the ones that were shorted))

Are any of the transistors heating up when you power up the amp?

((The only ones heating up are U762, U761, the voltage regulators, and on the driver board R283, R282, R483, R482 got very hot, burnt my finger, they all had 38 volts across them, however R282 have 50.2 volts across it.))

If you measure the resistance across the blue capacitors (out of the board), do they read as open?

((I'll get to this later this weekend when I have a little more time, I will also re solder in the replacement transistors))

When you power it up, what is the DC voltage on the third leg (source) of the IRFB31N20Ds?

((-50.2v on the other side of the board, will test the side that is missing the transistors later this weekend))

What is the voltage on the third leg of the IRF9640s?

((50.2v on the other side of the board, will test the side that is missing the transistors later this weekend))


Place the black meter lead on the secondary center-tap of the transformer (just left of the body of R761) when measuring the voltage on the third leg of the transistors.

(( When I do this my meter only reads a voltage of 50.2v on every other transistor, the other transistors make my meter automatically switch into a frequency test range, yet I was testing with no input signal))

What is the DC voltage across the following diodes? These are the orange diodes on the driver board.
D271 ((.051v)) Im assuming because of the missing transistors?
D272 ((11.93v))
D471 ((11.76v))
D472 ((11.86v))

Did you replace any of the transistors on the audio driver board?

((Nope, didn't even do any testing on there yet until testing those zenier diodes.))

Can you take a photo of the bottom of the driver board? Zoom in so that you only capture ~1/3 of the driver board in the full frame. All I need to see is from Q981 to the edge of the board. Since you can't post high res images here, email it to me or post it on the tripod site.

((Im going to see if my brother can hook me up with a personal web hosting site for my pictures tonight, I am useless when it comes to some computer stuff))

[Perry Babin]

D271 is probably shorted (or has shorted driver transistors across it). These often fail when the outputs fail. Find the driver transistors (probably 4 transistors - 2 parallel emitter follower pairs) connected to this diode and pull them from the board so they can be checked without interference from other components.

There may be open resistors under the board. The 1 ohm resistors commonly fail. In this type of amp, you can generally find the drivers for any goup of outputs by checking for continuity between the gate of the output and the emitter of the drivers. If the 1 ohm resistors are intact, you can find all 4 drivers. If the 1 ohm resistors are open, you will find only 2 of the driver transistors but from there is will be easy to find the other two.

[intensem1rider]

Well I took a whole bunch of new pictures and posted them on photobucket but it just wont let you zoom in to view the close up, I took 8MP pictures so you could zoom right on in.

Heres the link : http://s249.photobucket.com/albums/g...ntensem1rider/

If you see a picture that you want a full picture of I can e-mail it to you, unless you have an e-mail account that can handle all the pictures.

I soldered in the transistors again and powered it up and I read identical voltages as the other side of the board so thats a good sign. And I did test the wafer resistors on the bottom of the driver board and a 1 ohm resistor was open (R275) And I think Q274 may have gone with it, but im unsure as I don't know what im testing for in the range of resistances in the transistors.

[intensem1rider]

The last link may have not worked, try this: http://s249.photobucket.com/albums/g...ntensem1rider/

[Perry Babin]

Does your meter have a 'diode check' function?

Email me IMG_0211 in full res. babin_perry@yahoo.com

If Q274 failed, Q284 has likely failed also. Even if it hasn't failed, it must be replaced because the transistors are in parallel and need to be a matched pair.

[intensem1rider]

Yes, it does have a diode test function. And how would I go about getting that surface mount resistor off the board?

[Perry Babin]

To remove the SMD resistors, apply new solder to both sides. Heat one side for about 2-3 seconds. When you move the iron to the other side and the solder melts, the resistor should slide off of the pads. Don't push it onto another component or pad.



With your meter on diode check...

If the transistor is a 2SA1023, place the black meter lead on the base (third leg). When you touch the red lead to either of the other legs, the meter should read ~0.6v. If you read something near 0.0v or the meter reads open, the transistor is defective.

There should be no continuity between the emitter and collector (legs 1 and 2). Set the meter to ohms and measure the resistance between the emitter and collector. There should be no continuity between the two no matter the polarity of the leads on the legs.



If the transistor is a 2SC1027, the placement of the black and red leads will be reversed but otherwise the readings will be the same as above.

[intensem1rider]

Q274 and Q284 were both bad, I removed them from the board to test. They both were A1023's

Where is a good place online to order parts like this? I have tried newark and mouser in the past.