Newark and Digikey are Sanken dealers. Mouser sells Toshiba but not old stock that everyone is looking for. Sanken has discontinued a lot or their larger transistors but the output devices used in this amp are available from Digikey.
This drivers are out of production, as I know. I would change them with 2SC4883A/2SA1859A, which are available from Digikey.
Sajti
Sajti, thanks for the recommendation - added to Digikey basket.
Seems most of the devices are hard to find. Even the temperature sensor is out of production. I'm not sure what characteristic to look for in the replacement. Original is 2SD669A. I found KSC2690AYSTU-ND as potential alternative. Would that seem ok?
It depends what is between drivers and outputs.
A lot of my designs use 390r in series with mosfet gates and so the resistors rarely burn.
If you have bi polar drivers into bi polar outputs then there is a low impedance between them, and the drivers can easily be taken out too.
I find with irs2092 class d amps if the mosfets go they often take the 2092 with them.
So now I just replace 2092 too as part of the course.
Its cheaper than just changing mosfets then they blow again.
Ok, so thanks to the help on here, I now have replacement parts. Some of the parts I needed were on back-order so took a while to come.
And as advised, I have now replaced (on the bad channel):
- All output transistors
- Drivers
- Temperature sensors
- Emitter resistors (both channels)
I made a current limiting lamp lead and turned the amp on with the lead in place. The lamp lit brightly, I got scared and quickly turned it off, then tried again, the lamp starts bright then gradually dims - I presume this is the power supply caps charging then current drops as caps are charged.
Voltage across the emitter resistors starts at about 0.5mV then rises to about 1.0mV after a minute or so, but there is some discrepancy between some individual output devices, one or two measure 2.0mV when others are at or below 1.0mV.
DC offset is around 10mV
I haven’t left the amp on for very long but it doesn't seem to get warm at all. Could this be due to the lamp tester limiting the current?
One other concern is that there is a relay in the power supply and when turning the amp on, it clicks a few times before allowing the amp to power up. It's a bit like a car struggling to start with a flat battery and firing slowly for 5 or 6 cranks before starting. Could this be related to the current limiting or a bigger issue elsewhere?
Should I fire up without the lamp, or does it sound like there still may be issues?
And as advised, I have now replaced (on the bad channel):
- All output transistors
- Drivers
- Temperature sensors
- Emitter resistors (both channels)
I made a current limiting lamp lead and turned the amp on with the lead in place. The lamp lit brightly, I got scared and quickly turned it off, then tried again, the lamp starts bright then gradually dims - I presume this is the power supply caps charging then current drops as caps are charged.
Voltage across the emitter resistors starts at about 0.5mV then rises to about 1.0mV after a minute or so, but there is some discrepancy between some individual output devices, one or two measure 2.0mV when others are at or below 1.0mV.
DC offset is around 10mV
I haven’t left the amp on for very long but it doesn't seem to get warm at all. Could this be due to the lamp tester limiting the current?
One other concern is that there is a relay in the power supply and when turning the amp on, it clicks a few times before allowing the amp to power up. It's a bit like a car struggling to start with a flat battery and firing slowly for 5 or 6 cranks before starting. Could this be related to the current limiting or a bigger issue elsewhere?
Should I fire up without the lamp, or does it sound like there still may be issues?
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