There are three transistors on the left side that have burned up under the heatsinks and i cant figure out y or where to find replacements for them this was a used amp and when i was taking it out of my old car the RCA cables were melted togather
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Re: amp has burned up
You'll need to replace all three transistors and any other in the same line (unless they're divided by high power diodes). Make sure you check all resistors before replacing anything. Search www.digikey.com for parts, they should have the exact transistors-just put the numbers on the transistors into the search field.
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means there an internal problem with the audio side of the amp and that the power side is working fine. normaly it is a blown transistor on the audio side. take the cover off and see if you can smell anything burnt and take the heatsinks off the transistors and inspect them.
Check TR22 which is a 2sc1957 transistor mounted on side of case near heatsink for driver and final, left rear with speaker cover removed. Make sure the legs are not contacting case. Then check resistors R115, R116, R117 for open circuit and C133 for continuity.
I figure that 2sc1957 transistor is shorting to case or failed. A 2sc2314 is a sub for this transistor.
One or more of the power transistors are shorted. There are eight
transistors in the amplifier section - 2 high & 2 low for each
channel. This unit is difficult to open up to work on.
Unplug unit and check speakers with a multimeter to make sure they are not shorted.
Take off front panel (8 screws).
Remove power supply shield with yellow tape (2 screws).
Remove 2 screws holding top of power supply, loosen bottom screws.
Replace front and hold in place with a couple screws.
Turn unit around.
Remove screws holding heatsink (6 screws)
Open rear storage door.
Carefully pull amp section out, being careful of tightly routed wires. Note any connectors you disconnect.
The amplifier is the board on the top, the power supply is in the silver box.
Push the power supply forward and loose the black screws holding the amplifier board bracket closest to the heatsink.
Loosen the top brass screws holding bracket to heatsink and remove the bottom screws.
Remove all eight of the screws holding the transistor brackets &
transistors to the heatsink. Look and take careful note of how the
plastic insulators weave through the transistors. If you get this
wrong, you can short out the whole amplifier when you turn it on.
Slide the amplifier board down and out where you can get to the bottom.
Note the wires and connectors going to the small protect board over the
Check the transistors with a multimeter to find the shorted ones.
Remove and replace bad transistors. These are connected in pairs.
Reassemble in reverse. Be careful of reconnecting wires and
insulators. Don't test until the amplifier PCB is back in place and
you're sure of all wires. If the PCB is touching the power supply,
you'll short it out.
First look inside and determine which is the left channel. Then look at the area around the heatsink. Examine the semi-conductors for damage. Remember it's a stereo amp, which means it is just two mono amps put together. So the right side parts will be the same as the left. So if you find something destroyed, it will have a copy part on the other channel. If they are transistors you can test these with an Ohm meter.
Another way of testing is with a screwdriver. If you touch a part (audio) with it (don't short it) it will buzz. So if it buzzers on the right it should (in the same place) on the left.
DO NOT TOUCH POWER PARTS.
Oh, oh... got one on the bench now... There is a design defect that causes a short and destruction in the power amp portion.
Do a test: Plug headphones into the main 1/4 inch jacks. The sound won;t be very loud since these are line outputs, not for headphones.
IF you get sound out those, then one or both power amps are dead.
Worst case: if one amp is dead, several parts including three power MOSFET transistors are fried for any of the dead channels.
The failure of the amp can wipe out the main power supply. If you effect windows light up, then the small power supply is operating.
If the big supply is fried, there are two large MOSFET switching transistors that are gone. Often several smaller transistors and dides and resistors and one switching IC goes. MOST of these are surface mounted parts and would be beyond the scope of what you can repair.
I am trying to contact Behringer about the flaw but haven't heard back yet.
The nature of the flaw is this: The is insufficient clearance on an internal circuit layer from the edge that fits into a slot in the power amp heatsink. Any humidity that enters can cause the insulation to breakdown and arc to the heatsink causing a chain reaction.
I repaired one of these already before finding the cause, but this one had a smoking gun! I just yesterday milled out the slot deeper and wider and will put insulating tape to prevent further arcing. The arcing that had occured burned away the internal layer and the connections. I will replace thoose with hardwire.
Repair of this problem is time consuming to weed out all the blown parts and to safely bring the unit back to life.
The current unit I am working on took out ONLY the power amp. A 30 milliohm resistor went up in smoke making a real mess. All three power MOSFETS are gonzo and a zener as well... don't know what else I will find. The previous unit was worse as the power supply was wiped as well.
Hi again! Been thinking about this and you might not need to wait for someone to answer. I assume the transistor in question has blown apart or burnt up so you can't read the number?
However does it come off the heatsink as part of the main amp? If it does then it might have a brother around it. For if it is say the left or right channel transistor, then the other channel will have the same type transistor. Remember the left and right channels are copies of one another. If you see 4 transistors on the heat sink then it's a push-pull amp. They work in pairs, one pair for each channel. By the way it's best to replace the pair, even if only one is blown.
If on the other hand the blown transistor is from the power supply section, then you will have to wait for someone to help, or get the service manual.
it has to have some type of allen head screws holding it directly to the heatsink . phillips screws , look closely on the amps board . transistors may also be stuck to crayotherm (material under inputs and out puts ) with that white paste everyone slabs all over them,heat and time makes it like glue .
Sounds like you have fried your output transistors. They can be replaced if u have the patience and know-how. Also check the resistors near the transistors. Some of them may need to b replaced too. I fu replace the transistors and the resisitors are still fried, u run the chance of burning up the new transistors again. I usually just replace both items since it's not that expensive and I'm doing the labor. What have you got 2 lose?
Sounds like you may have a shorted switching Transistor in the switch mode power supply causing a short to ground. If you are technical enough. Remove power remove cover and do a continuity test on the transistors on the heatsink. non of them should read zero resistance between the three legs. in all connection configuration you use to hook up your meter. If one or Two or even all of them do you must replace with proper part.