Which power transistors to put the insulation pad when mounting to heatsink in a SW380 subwoofer. I see not all transistors, but 4 of them, requires mica insulation pad when mounted to the heat sink.

You could try contacting the US distributor [email protected]
Maybe try ebay. Be sure to spell it correctly: Wharfedale

If there is a subwoofer with an end-amplifier inside there could be a capacitor problem by deformed or leaking capacitors but also look at the heatsink where are often mosfets placed or vintage conventional NPN / PNP transistors and they are in most times short -circuited between GDS gate drain source if its a mosfet or between base collector emitter if there is a transistor is used maybe when an active transistor output stage is used is it also handy to make a little test bank , to make a serial connection from mains over a 200 watt lamp. this in order to save fuses.

Beware ! The accu is example for mains 120V and the meter for the subwooferamp powercable (not for the speakercable) its only an example for a connexion diagram how to spare the fuses in a test mode. if there is a fuse placed

Disconnect power from the unit. Open it up to gain access to the coil and controller. Disconnect the coil and use an ohmmeter to check its continuity. If it is open, replace it. Also inspect the connector pins and sockets to make sure they are not corroded or oxidized. (If the connector shell or the wire insulation at the connector show signs of overheating, this is very likely where the problem is.) Clean and polish, or replace the connector contacts if necessary.

If the coil, coil wiring and connector pass, then inspect the controller board - if the coil drive switching device (probably a transistor for a high-frequency induction system) runs hot, it may cause thermal fatigue in the solder on the bottom of the board, leading to a cracked connection. The repair is to remove the burned solder, polish the affected transistor lead with fine-grade Scotch-Brite abrasive, then resolder with lead-free (i. e., high-temperature) solder. It may be necessary to wrap a short piece of 18 or 20 AWG wire around the transistor lead and bridge it across the pad to the circuit trace going to the coil connector if the board is damaged from the heat.

If both of the power connections on the transistor are overheating, the transistor probably does not have a good thermal connection to its heatsink. In that case, you should remove the transistor, clean up the heat sink transfer grease, put a thin film of new heat transfer grease on the transistor, and remount it. (This is not ordinary grease, it's a compound specially made for the job - you can get it at any electronic supply or computer component supplier). If there is a mica insulator sheet between the transistor and heat sink, carefully clean both sides, and apply the heat transfer compound to both sides of the insulator instead of the transistor. Do not apply too much; you want just enough to make sure there is good thermal contact between the adjoining surfaces. If there is a rubber-like sheet between the transistor and heat sink, but no grease, inspect the sheet for tears or hardening, and do not use grease for reinstallation. You may find that the transistor was not flat up against the heat sink because the lead bends held it away from the mounting surface. In that case, tweak the leads using two pairs of needle nose pliers - one next to transistor case to keep the bend from cracking the seal at the case, and the other to bend the lead.

NOTE: do not touch the gate/base lead (left side lead on most power transistors) with your fingers or a tool unless you are first touching the other two leads to discharge any static electricity buildup. The gate is easily damaged by static electricity from your clothing, even if you can't feel it discharge. Likewise, do not put the transistor on plastic unless it is the anti-static kind. The entire controller board should be considered static-sensitve. Handle it only by the edges; avoid touching the circuitry. If you must remove it, place it component side down on your work surface so static discharges from the work surface won't reach the printed wiring on the board, or use an anti-static work mat.

If these measures do not solve the problem, you may have to replace the controller board.

I would contact Wharfedale USA or Wharfedale.co.uk

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 amplifier.
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.

Good luck, I told you this wouldn't be easy!

No! I have two of the PMP5000 and one PMP3000.

I could tell you what parts are blown. If nothing lights up what has happened is the power amp (Usually the rearmost amp) has arced and destroyed the three switching transistors and a Zener diode and sometimes a metering resistor and two surface mounted transistors. So far parts cost is about $20 and a LOT of labor.

Since the fuse blew, it is possible as is often the case, that the power supply is also damaged. Now the total parts cost is $50 as two expensive IGBT's are blown, a regulator IC and four driver transistors for the IGBT's and one other surface mounted transistor and usually a diode. If a fuse has been repalced, then often a pair of power resistors associated with softstart are blown. A lot of labor is necessary on the power supply to remove the heatsinks that the IGBT's are on to replace them.

If the amp module (HCA2400) were the only thing, you can get those online complete for $175. Repair of those requires a lot of skill carving out burned board between layers of the multilayer board and restoring connections with jumpers.

You are probably looking at $300 parts and labor to restore this unit. I fix them for my own use, not others.

There is a weakness in insulation between internal and external layer of the circuit board near the rearmost amp and if you play it real load and had a speaker lead come loose the unit can arc and it is all over. There is also a polarity hazard. PLEASE read my tip on here in that regard about this. This applies to the PMP3000, PMP5000, PMP1280 amps.

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 amplifier.
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.

Good luck, I told you this wouldn't be easy!

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.

Anything in the power supply will cause it, look for damage or burnt parts, anything on heatsink. A transistor with a short circuit. For instance if you put an ohm meter probe to the leg of one and the other probe on to another leg, it will be read on the meter as if you had put your probes on the same leg.

That sound´s like overheat... chek if there is no short circuit in the output cables or if any speaker is damaged

Hope it helps