Blown Channel on an amplifier

Transistors don't really have values, just a number on them. Most Japanese transistors are numbered with a letter first, A, B, C, K, and then a number. When searching for a replacement you add the this at the start "2S" so 2SB500 for one marked B500. If you can't read a number due to damage, with stereo amps the two channels are the same. So if the left channel transistor has burnt up look at the right channel one, you will quickly see the parts around it will be arranged the same as the blown channel.

I would also replace 2sa992 (2pcs) and 2sc1845 on preamp board- sometimes they look ok when you test them by regular meter. Check 1.2 kOm and 4.7ohm resistors at preamp pcb. Check diodes on output pcb (could be smd type, connected from base of output transistors to emitter i think)

Unfortunately there is little we can do directly. The output transistors are likely to be shorted on the bad channel. This is not a DIY repair for most people. Expect a repair bill in the $80 range for parts.

Dan

Have you checked the final transistors on that weak channel? They may look fine but may be weak. You can pull them and check them on your multimeter with the diode check and cross it with the data sheet for that transistor.

Check fuses on the amplifier's power wire to make sure it's not blown. Replace it if necessary. Also check for blown fuses on the amplifier itself. The problem could also be the amplifier's remote wire. This wire (Usually blue) needs to be wired into the stereo's power wire (usually red or yellow).

Usual problem is the Channel A amplifier has burned and blown the switching transistors. Usually an internal board arc occurs and unless very skilled at board work of clearing the burned area and replacing the components you are better to replace the HCA2400 amplifier module... about $160

wes online

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.

Take a ohm meter and measure resistance from emiter to collector should have a few kilo ohm on output transistor.
If no ohm meter available , remove output transistors from circuit.
note position of transistor . you have a NPN and a PNP for each channel.
Replace fuse and power up. If fuse blows check bridge in the power supply.

80% of the time output transistor burn and blow the fuse.
before replacing output transistors check driver transistors they probably burnt also

Hi there, sounds like you may have a short to ground on the output transistors. Does it have transistors or an IC output. It is most likely that you have not replaced a mica washer or insulator. Check to ground with a meter from the case of the output devices.