Hello
I’m at the testing stage of a K8060. The amplifier worked for about 20 minutes then blew-up the TIP147G output transistor. Which now has a short circuit between the collector and emitter. The TIP142 seems to be OK.
The powers supply measures +/- 45V DC on the rails and the transformer input (240V) is fused with a 1A slow blow fuse.
During the test the amp was being asked to drive a pair of 8 ohm speakers in parallel. The input was from a bass guitar pre-amp and was well turned up! It’s difficult to say what the actual input swing was.
I suspect I may have driven the input beyond a reasonable limit.
What input swing would you expect the K8060 to tolerate before destroying the output transistors?
Thanks
[quote=“VEL417”]+ and - 45VDC is a little beyond the max. input for safe operation.
We recommend a 25-30VAC transformer.
At 30VAC, the theoretical max. DC voltage is 30x1.41-1.4=40.9V
[/quote]
I have changed the transformer for the one supplied by Velleman and the DC voltages on the test points are +/- 43.7V not much different from the Maplin one! I’ve replaced the dead transistors and all is now working OK.
Now here’s the thing I am proposing to build a monitor circuit to indicate the presence of 600mV peak or whatever is a safe input level.
I want to establish the actual peak to peak input to limit power dissipation to 100W RMS. I am testing with a 4 ohm 100W resistor connected to the output. With 600mV 200Hz on the input I see 18V peak to peak across this resistor. Calculating the output power: Current = 18/4 = 4.5 amps. Power dissipation = I^2 * R equals approx 81W peak ~ 51W RMS. The heat sink is just beginning to get warm during this test.
In theory I should be able to push this quite a bit more. The TIP142/147 data sheet says maximum 10A continuous collector current. 15A peak.
So my question is what is your recommendation for how much further I might push the measured dissipation?