Blown transistor output how to replace? - Sony STR-DE595 5-Channel Amplifier

Hello, sorry, we do not sell repair parts to end users. Only authorized repair centers. Thank you, Onkyo USA

Tough one. I repair these for a living. A number of possibilities exist. Likely output transistors are blown on the bad channel. Fuses are likely blown. If the fuses are BLACK inside, don't just put new fuses in, more damage WILL occur. This is a bit more than 'good with a soldering iron' will fix. You need to know how to test an output transistor. You need to look up the transistor type so you know what it is. A service manual will be a big help (I could not find one online.) If more than two outputs are gone on the one side, all should be changed, they are supposed to be MATCHED. Remove and replace all damaged outputs, or replace them all if two are blown. Find the driver transistors and check them for short circuits. After repair, start the amp on a dummy load of a 250watt light bulb to prevent destroying the amp if there is a problem. If you are unsure of any part of this, find an electronics technician to help.

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)

The cheapest option is to replace the transistors (a quick check on google will tell you how much they are). If they are common transistors you will be able to find them and get them quicker then searching for a board that could be no longer being made.

If the Horizontal output transistor was blown the flyback will need replacement. You can get replacement flybacks from www.tvrepairworld.com

If the speaker is not blown, there must be an output capacitor. If no output capacitor, and you have a blown transistor the speaker will blow from DC current. You can further check the transistors with a multimeter. A transistor looks like 2 diodes and you should be abobe to test with a mulimenter like a diode test.

Amp Failure:
There are many different ways that an amp can fail but the two most common failures are shorted output transistors and blown power supply transistors (< those are not blown). There are several types of protection circuits in amplifiers. The most common are over-current and thermal. The over-current protection is supposed to protect the output transistors. Sometimes it doesn't work well enough to prevent the failure of the output transistors but it will work well enough to shut the supply down before the power supply FETs are destroyed. If the amp remains in protect mode, goes into protect mode or blows the fuse as soon as the remote voltage is applied, shorted output transistors are almost certainly the cause. If the fuse protecting the amp is too large, if the protection circuit doesn't respond quickly enough or if the power supply is poorly designed, the power supply transistors may fail. If you see a lot of black soot on the power supply transistors (near the power transformer), the power supply transistors have failed. Soot on the board doesn't necessarily mean the transistors have failed. Sometimes, technicians don't clean up the mess from a previous failure. Transistor Failure/Checking Transistors:
In general, when a transistor fails, it will either short (common for output AND power supply transistors) or open (common for power supply transistors). Transistors act like valves. They control the current flowing through a circuit. A shorted transistor acts like a valve that's stuck open (passing too much current). In the case of an output transistor, the shorted transistors tries to deliver the full rail voltage to the speaker output terminal. If you've ever seen a damaged amp that pushed or pulled the speaker cone to its limits when the amp powered up (common on some Rockford amplifiers), that was almost certainly due to a shorted output transistor. When checking transistors, you most commonly look for shorted connections inside the transistor. You do this by using a multimeter to look for low resistance connections between the transistor's terminals.

Seems as you have blown an output. Seek repairs.

the output is blown. It is in need of service.
There are many different ways that an amp can fail but the two most common failures are shorted output transistors and blown power supply transistors (< those are not blown). There are several types of protection circuits in amplifiers. The most common are over-current and thermal. The over-current protection is supposed to protect the output transistors. Sometimes it doesn't work well enough to prevent the failure of the output transistors but it will work well enough to shut the supply down before the power supply FETs are destroyed. If the amp remains in protect mode, goes into protect mode or blows the fuse as soon as the remote voltage is applied, shorted output transistors are almost certainly the cause.

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.