Help Orion 250g4 keeps blowing fuses

[Jstyl]

I was hittin really hard and my amp tuned off then came back on then died completely so i wen and replaced the 2 30 amp fuses on the amp and it immediately popped them so i took it out and seen that my ndp7060 fairchild transistor was craked open smelt nasty so i tested all of the transistors on both sides with a multimeter set on ohm they all read the same,Im new with a multimeter.I just need to know what i need to look for cause after i replaced it i put 2 10 amp fuses in in case of damage and as soon as i turned the key they popped.Any one have any idea whats wrong?

[Perry Babin]

The power supply FETs (the 70N06s) have failed. They may have failed alone or they may have failed due to shorted transistors in the audio section of the amp. Did you read near zero ohms between the legs of any individual transistor on the other side of the amp?

If none of the transistors on the other side of the amp are shorted, you will need to replace ALL of the 70N60s. Also check the resistors near Q57-Q60 (especially the 10 ohm resistors that connect leg 3 of the MPSA56s to ground). The MPSA56s have likely failed. I'd suggest replacing Q57-Q60.

The circuit board designations are from a 250R. They may be different on your amp.

After replacing the defective parts, clamp them to the heatsink before applying power. Use a single 15 amp fuse when you initially apply power. If the fuse blows, there is likely another fault.

[Jstyl]

What are the q's and what are FET'S the power side is what blew the ndp7060 are on the power side also i checked every single ndp7060 and they all read the same i get ...On the first is red, middle nothing and last negative i read 000.49 then when i put the negative on the middle and the positive on left or right it climbs high on all of them to 0.398 on every single one.also do the same thing on the audio side but there's 2 different transistors there's 2n6488 and 2n6491 on every transistor i never read 0 ...Here some pics maybe you can paint arrows on what i need to do and how i should test them properly.I really appreciate your input a lot Thanks-Jeremy also on the 3rd pic last pic is that the correct setting to measure transistors? and the 2nd pic that one of the transistors i replaced figured you could diagram how to touch the multimeter leads to them Thanks



http://img208.imageshack.us/my.php?image=1006519ky7.jpg


http://img120.imageshack.us/my.php?image=1006513ms0.jpg

http://img151.imageshack.us/my.php?image=1006526oc0.jpg

[Jstyl]

Also say i replace all the ndp7060's and i power it up and the 15 amp fuse blows will that damage anything again or no,cause i just ordered "20" ndp7060's just now those are on the power side .I didn't see any numbers indicating that the 2n6's were damaged on the audio side but then again i didn't see that on the power side with the ndp's either except the fried one but i hear that when one goes it usually it takes out a bunch with it.Now i did happen to see 3 other ndp's with dark spots on the side that is pressed against the tape and they were pretty far apart from the exploding one and the 2n6's on the audio side had none of that of any of them.

[Jstyl]

Oh and one more thing lol ...I saw that on quite a few had solider that looked like it had oozed out a lil on the back side that is pressed on the tape on the ndp's on the power side it was soo flat though looked like maybe it was assembled that way but maybe it melted inside from the heat and being pressed up against the tape made it bond to itself well;making it look like it would be like that i dunno just throwing this at you Thanks for taking the time to help me out

[Perry Babin]

If you clamp the 70N06s and use the single 15 amp fuse, that should offer enough protection to prevent blowing them again. When you power it up, you should have all transistors clamped. If it powers up, the output transistors (2N6488/91) can overheat and fail quickly if not clamped.

Did you order the MPSA56/06 driver transistors?

Did you check those resistors?

The solder inside the transistor expands and is forced out the back of the transistor. This is common. It's so thin because the transistor was tightly clamped to the heatsink.

[Jstyl]

MPSA56/06 driver transistors? i don't know which one this is on my orion am due to i have a ton of those little guys on my board.Is it a must have?

[Jstyl]

ok yah i check a few MPSA56 and i found at least 3 that were dead due to no numbers and test other with numbers on all 3 pins.Shoot wish i would of ordered them with my ndp shipping is a more them 25 of them guys lol $6.25 for 25 of them btw if you need to know of a good place for prices it "MCM Electronics" cheapest I've found yet and you don't have to buy bulk like the other company's

[Jstyl]

Ok i just counted what i have;so you think all of these are risky of being bad?I mean seems like i mise well buy every resistor,diode and transistor that exist on the board lol


10" -mspa56

10" -mspa06

3" -2n5639

[Jstyl]

What does it men a when i touch my leads to the out side left and out side right and the number doesn't stop climbing but when i touch ground to the middle and positive to the left out side i get a quick solid number?