basil13
Active Member
Hi All,
I have been working on a stubborn MC 250 with some help from c_dk and thought I was successfully done with it. This has been my first MC 250 to work on and has been an adventure.
After a few days of play testing, I noticed some distortion on one channel. I put it on the scope and sure enough there is some oscillation on the positive half cycle (see picture).
It only happens under load, it is clean otherwise.
The channel is using the original drivers and output transistors. The class A board still has its original transistor as well. However, I had to essentially rebuild the class A board with many new parts.
The 0.56 ohm 5 watt wirewound resistor was replaced previously with a NTE, I have read that Mac does use NTE parts, is this a Mac replacement (see picture)? If not, could it be the source of my problem?
Any other parts I should look at troubleshooting?
An oscillation problem is a new experience, so any other advice would be appreciated.
Regards
Bob
I have been working on a stubborn MC 250 with some help from c_dk and thought I was successfully done with it. This has been my first MC 250 to work on and has been an adventure.
After a few days of play testing, I noticed some distortion on one channel. I put it on the scope and sure enough there is some oscillation on the positive half cycle (see picture).
It only happens under load, it is clean otherwise.
The channel is using the original drivers and output transistors. The class A board still has its original transistor as well. However, I had to essentially rebuild the class A board with many new parts.
The 0.56 ohm 5 watt wirewound resistor was replaced previously with a NTE, I have read that Mac does use NTE parts, is this a Mac replacement (see picture)? If not, could it be the source of my problem?
Any other parts I should look at troubleshooting?
An oscillation problem is a new experience, so any other advice would be appreciated.
Regards
Bob
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