Hi, I have a Sony STR-DB930 and could use some help!
I was playing it last night (at high volumes, as usual!) and suddenly, the protector light started flashing, and the sound shut off. I tried to restart it a couple of times, but just saw green flashes from inside - I think it was the two fuses on the DC board blowing.
I opened it up, and with the help of The Google and youtube started troubleshooting. The two fuses (F801 and F802) on the DC board were blown. I started checking the emitter resistors, and all of them seemed good - they all measured ~0.2 ohms from center to end, and ~0.4 ohms across the two resistors. They also all measured between 50 mV and 150 mV from the center pin with the unit powered up.
I then started going through each output transistor, measuring from the collector pin to the emitter pin. They all measured about 0.5 volts, but one of the transistors on the right front channel measured 0.2 V, and the other resistor on that channel was 0 V (part MN2488). So I'm assuming that I need to replace the transistor that measured 0V, but do I also need to replace the one that measured only 0.2 V? Or is it not a problem? It's counterpart on the left channel measured 0.6 V. Also, is there anything else I need to check? I read something about possibly having to replace some resistors too.
Finally, how much should it cost to get something like this repaired? I have very little experience here, and will have to really dig into this thing deeply to get to that resistor. Any advice from the experts?
Thanks!
Paul
I was playing it last night (at high volumes, as usual!) and suddenly, the protector light started flashing, and the sound shut off. I tried to restart it a couple of times, but just saw green flashes from inside - I think it was the two fuses on the DC board blowing.
I opened it up, and with the help of The Google and youtube started troubleshooting. The two fuses (F801 and F802) on the DC board were blown. I started checking the emitter resistors, and all of them seemed good - they all measured ~0.2 ohms from center to end, and ~0.4 ohms across the two resistors. They also all measured between 50 mV and 150 mV from the center pin with the unit powered up.
I then started going through each output transistor, measuring from the collector pin to the emitter pin. They all measured about 0.5 volts, but one of the transistors on the right front channel measured 0.2 V, and the other resistor on that channel was 0 V (part MN2488). So I'm assuming that I need to replace the transistor that measured 0V, but do I also need to replace the one that measured only 0.2 V? Or is it not a problem? It's counterpart on the left channel measured 0.6 V. Also, is there anything else I need to check? I read something about possibly having to replace some resistors too.
Finally, how much should it cost to get something like this repaired? I have very little experience here, and will have to really dig into this thing deeply to get to that resistor. Any advice from the experts?
Thanks!
Paul
Do you mean that you measured the voltage between the base and the emitter?
The voltage from the collector to the emitter should be equal to the power supply voltage.
I measured from the center pin to the pin on the right, as you face the transistor mounted to the heat sink. Should the receiver have been powered up during that step? I was following the steps I saw in a youtube video with a similar amp. Sorry, I'm not very experienced with this!
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