I have picked up another non-working MX-1000 a few months back. The amp would not come out of protection. Today I decided to take a shot at fixing it.
It turned out to be a bad left channel.
After some investigation, I found:
one blown driver (Q315 - 2SA1306), replaced with 2SA1837 and replaced its pair which was not bad, but replaced it anyway, with 2SC3503
one blown final transistor (Q317 - 2SC3280), replaced with MJL3281
Base-Emiter resistor for Q317 (R367 - 68ohm)
Emiter resistor for Q317 (R317 - 0.22ohm)
On the power supply board I replaced two transistors
Q513 (2SC3416) replaced with KSC3503
Q515 (2SA1352) replaced with KSA1381
D511 (1SS133) replaced with 1N4448
The amp comes out of protection now and I get sound on both channels, BUT...
I adjusted the right idling current (good channel) to 10mV - no problem
I tried to adjust the left channel, the channel I thought i fixed, and I get 20mV at the minimum, thus the idling current remains high on the Left channel, which I thought I fixed. I do not have to mention that the heat sink of the left channel is much hotter than that of the working channel.
I know I missed something, but do not know what. Does anyone have any suggestions? Thanks for your help in advance.
It turned out to be a bad left channel.
After some investigation, I found:
one blown driver (Q315 - 2SA1306), replaced with 2SA1837 and replaced its pair which was not bad, but replaced it anyway, with 2SC3503
one blown final transistor (Q317 - 2SC3280), replaced with MJL3281
Base-Emiter resistor for Q317 (R367 - 68ohm)
Emiter resistor for Q317 (R317 - 0.22ohm)
On the power supply board I replaced two transistors
Q513 (2SC3416) replaced with KSC3503
Q515 (2SA1352) replaced with KSA1381
D511 (1SS133) replaced with 1N4448
The amp comes out of protection now and I get sound on both channels, BUT...
I adjusted the right idling current (good channel) to 10mV - no problem
I tried to adjust the left channel, the channel I thought i fixed, and I get 20mV at the minimum, thus the idling current remains high on the Left channel, which I thought I fixed. I do not have to mention that the heat sink of the left channel is much hotter than that of the working channel.
I know I missed something, but do not know what. Does anyone have any suggestions? Thanks for your help in advance.