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Blown JBL PX300.4 Amplifier?


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y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 4:06 PM / IP Logged  

Here is the layout of the traces:

Blown JBL PX300.4 Amplifier? - Page 7 -- posted image.

Once again - the blown transistor is the bottom right most one. (On the red line with yellow junctions)

i am an idiot 
Platinum - Posts: 13,686
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 7:06 PM / IP Logged  
You have yellow and purple dots on all 4 corners of the 2 pairs of transistors.  What are the part numbers on those transistors?
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 7:16 PM / IP Logged  

Ok, wel they arent on all 4 corners of the transistors...the transistors only have 2 poles - there are resistors right next to them to.  Its weird...they're wired in parallel.  Anyways the numbers written on the side is:

K-632

A1266
GR

i am an idiot 
Platinum - Posts: 13,686
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 7:59 PM / IP Logged  
The transistors have 3 legs.  That one you gave numbers on is a 2SA1266.  There should be 2 of those and (2) 2SC****.  I looked again at your picture.  You have 4 yellow dots surronding 2 transistors.  4 Dots around each.  And you have 4 violet dots around 2 more transistors.  I am sure that 2 are the 2SA1266 you mentioned earlier.  There should be (2) 2SC****.  I think that the 2SA1266 is bad, but I need to know if there is a 2SC there also.   The 2SA connected to the resistor that was connected to the exploded transistor will need to be removed from the board.  If you notice at the bottom of the board, all 3 of the legs of that transistor are bent over to hold the transistor in the board while it was being sent down the line to get soldered.  These bends need to be taken out of the legs in order to remove them without damaging the board.  One leg will be bent one direction and the other 2 are bent in the opposite direction.  I add solder and use a small flat blade jewelers screwdriver to straighten the leg out.  With the screwdriver under the end of the leg, heat the joint and gently lift up intil the leg is straight.  Repeat for the other 2 legs.  Now if you have a pair of Hemostats, they will help here.  Clamp them onto the transistor at the top of the board, flip the board over and heat up the 3 joints all at one time.  The transistor should easily fall out of the board.  I will post a link to a page that will show you how to check a transistor. 
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 8:08 PM / IP Logged  

Ya your right...I missed the 3rd leg in the middle. 

Ok just so we are clear - the transistors we are talking about are roughly in the middle of the board, and look pretty much like half circles from a top view rigt?

The blue line, passes through 2 of them, and they are both surrounded by 4 purple dots each.

The red line passes through 2 of them, just to the right of the blue ones, and they too are both surrounded by 4 yellow dots each.
Right?

All 4 of them have the samething written on them which is:

K-632
A1266
GR

--- EDIT ---

So when you say the transistor connected to the resistor of the exploded transistor has to be removed, do you mean the TWO of them that are in the red line?

i am an idiot 
Platinum - Posts: 13,686
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 8:16 PM / IP Logged  
http://www.bcae1.com/ampfail.htm   was the page I was looking for, but I just noticed that there are instructions for checking NPN transistors but not for checking PNP transistors.  He is e-mailing me a link to a chart for you to fill out.  I will get that to you in an hour or so.
i am an idiot 
Platinum - Posts: 13,686
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 8:19 PM / IP Logged  

I need to know if there are 2 of the 2SA transistors?   Are there also 2 of the 2SC transistors?   I need to make sure that both types are present, before you go removing anything. 

y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 8:22 PM / IP Logged  
All four are 2SA, and none are 2SC.  I can start randomly looking for 2SC if you want.  Im sure they might be there SOMEWHERE.
i am an idiot 
Platinum - Posts: 13,686
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 8:52 PM / IP Logged  
The Chip west of the transistors, what is the number on it?   TL594. SG3525 ??
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 8:57 PM / IP Logged  

Ok I must not be understanding you correctly.  I appologize in advance.  I'm not quite sure why you quoted yourself - clearly because there is something in there that SHOULD be clearing something up.  But it is not... and for that I appologize.  I hope these pictures clarify something.

Blown JBL PX300.4 Amplifier? - Page 7 -- posted image.

Blown JBL PX300.4 Amplifier? - Page 7 -- posted image.

The chipset, which can be seen in the first picture had I not put writing over it, says:

58HJ1VK
TL494CN

---EDIT---

OMG the resizing of images is seriously bugged!  As a result I give up on reducing their width below 640.  Is there a way I can use Html code, rather than the buttons at the top of the bar?

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