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Blown JBL PX300.4 Amplifier?


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i am an idiot 
Platinum - Posts: 13,666
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 9:09 PM / IP Logged  
In the top picture, I can see the 2SC3198, but I can not see where it is. Are you saying that every transistor with the red lines pointing to them are all 2Sa1266s?   Where are the 2SC3198s?
I have never seen this before, but there may be (2) 2SA1266s per bank of FETs, Are the legs of the 1266s connected to another of the 1266s?
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 9:37 PM / IP Logged  

In the top picture the arrows indicate what letters they connect to.  The second picture was just showing that the arrows point to all the same sort of transistor which has the model # in clear view on one.  So yes I guess there are 2 different ? (one had K546 and BL, and the other has K632 and GR) 3198s.  Here is a clear picture:

Blown JBL PX300.4 Amplifier? - Page 8 -- posted image.

So, as you can see in the picture, the transistors that I orginally drew traces over have their center leg attached to each other. So the traces I drew actually cross then. 

The other random 2 A1266s, are connected by their left legs.  The bottom one has a trace that goes up to a cap, then a resistor.  From the resistor a trace on the bottom of the board goes to the top A1266, and it also branches out more to the left...Hope thats clear.

I'm not quite sure what you mean by FETs and stuff like that.  I do consider myself to be a smart guy, and I'm more than capable of doing whatever you tell me to do, and I learn quick also, but I have no training in electronics other than basic CEGEP physics...so like reading circuits, calculating resistance, capcitance etc.

i am an idiot 
Platinum - Posts: 13,666
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 10:07 PM / IP Logged  
FET = short for MOSFET = IRF-Z44 or 50N06   Do not remove any of these yet. Did you get the Z44s yet. If so I really recommend you purchasing 4 of These from Radio Shack. Wire the 4 in parallel, for a 2 ohm outcome. We will have to put the 44s in and mount the amp back in the heat sink, wire the resistors in series with the power wire and turn it on first for about 10 seconds. Let me know when you have the 44s and the resistors.
i am an idiot 
Platinum - Posts: 13,666
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 10:35 PM / IP Logged  
Here is the Link to check the transistors But remember we have decided not to do that at this point. Do not remove any of the transistors. You will have to click on the link at top of this page that says click here for bipolar transistors. If we were checking them. You may need to pull them out later, but for now, let's not.
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 10:36 PM / IP Logged  

kk

i am an idiot wrote:
FET = short for MOSFET = IRF-Z44 or 50N06   Do not remove any of these yet.

I already removed all 8 of the 50N06s remember?

i am an idiot wrote:
Did you get the Z44s yet. If so I really recommend you purchasing 4 of These from Radio Shack
 

I bought 8 new Z44s the other day, they're ready to go.  As far as the resistors go, do you think they will have them if I just walk into radio shack?

i am an idiot wrote:
Wire the 4 in parallel, for a 2 ohm outcome. We will have to put the 44s in and mount the amp back in the heat sink, wire the resistors in series with the power wire and turn it on first for about 10 seconds.
 

Ok, you said parallel and series - just want to make sure we're clear here.  You want me to wire the resistors in parallel to reduce overall resistance and wire than in series right? Are we getting these in lieu of a sealed beam? Like this:

Blown JBL PX300.4 Amplifier? - Page 8 -- posted image.

So I=V/R or 12/2 =6 amps.  Why is it that we want 6amps, why wouldnt we just want to use 1 resistor, and do 12/8=1.5 amps?

i am an idiot wrote:
Let me know when you have the 44s and the resistors.

Will do.

So lets make a checklist:

1)Install Z44s, exactly in place of the 50N06s

2)Buy 4 of thoses resistors
3)Do you want me to remove that transistor that you explained how to do before, or should I leave it in for now?  Im assuming leave it in.

i am an idiot 
Platinum - Posts: 13,666
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 21, 2009 at 10:45 PM / IP Logged  
Yes leave the other transistors in the board. Diagram is exactly right. Yes you should be able to walk in and purchase. I do not know if they will have 4 but they should have some. You may have to hit a couple stores.
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 21, 2009 at 10:55 PM / IP Logged  

Alright, well 2morrow I probabbly wont get to that because I have 2 exams, one from 2-5pm, and another from 7-10pm.  Prior to that I'll be cramming.  But I'll put the Z44s in tomorrow after the exams, and thursday I'll start the hunt.  Thanks again!

y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 24, 2009 at 8:16 PM / IP Logged  

Ok, well the Z44s are sitting happily in their new home on the circuit board.  I'm having trouble finding the resistors though - apparently Canada doesnt have radioshacks anymore - they're now called The Source, and its rather difficult to find those resistors.

I understand that I need to reduce the amperage going to the amp using resistors - but what is an acceptable range for the Watts and total ohms.  This way I can hopefully have a little more luck finding some.  I found a few 20 W resistors, but the lowest resistance was 200 ohms - and wiring 100 in parallel isnt exactly practical.  If within the next 2-3 days I cant find anything I'll order the ones from radioshack - if they deliver to canada.  After all - I'm still waiting for the Kapton tape to arrive before I can even put everything back into the heatsink.

i am an idiot 
Platinum - Posts: 13,666
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: April 24, 2009 at 8:44 PM / IP Logged  
If there is a problem with the drivers in the power supply, a 2 ohm resistor will limit the current to no more than around 7 amps. This will keep you from damaging anything if there is a problem. Without an oscilloscope, I highly recommend using some sort of current limiting device. You can buy an old sealed beam headlight and use it instead. The light will serve a second purpose too. If there is a problem the light will light up. If all is well, it will be very dim if lit at all.
Wait on the Kapton tape.
y2j514 
Copper - Posts: 94
Copper spacespace
Joined: April 26, 2007
Location: Quebec, Canada
Posted: April 28, 2009 at 4:33 PM / IP Logged  

Kapton tape came in, I put it in some nail polish remover to remove the sticky side.  But it on the heat sink and bolted the amp back up.  However, I ran into a tiny problem.  Radioshack doesnt exist in Canada anymore - I knew they changed it to "The Source by Circuit City", but I thought it was just a name change because every RadioShack became that - but apparently they aren't the same....and RadioShack.com doesn't deliver to Canada...sooo....

http://www.canadiantire.ca/AST/browse/4/Auto/AutoHeadlights/SealedBeam/PRDOVR~0203678P/GE%2BSealed%2BBeam%2BHeadlight%252C%2BH5006.jsp

will this work?

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