New to me amplifier has some issues with channels 1 and 4. Output is way down on both channels. Need to turn the input attenuation all the way up to get close to balancing with channel 2, same with channel 4 and 3. When bridged the 1-2 channel is way down on power compared to the 3-4 channel. Channels 5 amd 6 are fine.. I am using an DSO and test tones, but it was obvious in listening there is a huge power discrepancy. No distortion though, just low power.
Channels 2,3,5 and 6 all work fine.
I have messed around with the 4,5,6 selector amd that is set right according to the manual for the different configuration I have tried.
I am looking into protection mode this amp uses maybe that is the issue. I think grounding th PG terminal will shut the protection off.
Anyone have any experience with these amps or suggestions on where to start?
Channels 2,3,5 and 6 all work fine.
I have messed around with the 4,5,6 selector amd that is set right according to the manual for the different configuration I have tried.
I am looking into protection mode this amp uses maybe that is the issue. I think grounding th PG terminal will shut the protection off.
Anyone have any experience with these amps or suggestions on where to start?
You should try getting the service manual if it's still available:
Mac Service Manual MC420 & MC440 on pdf **FREE** | DiyMobileAudio.com Car Stereo Forum
Mac Service Manual MC420 & MC440 on pdf **FREE** | DiyMobileAudio.com Car Stereo Forum
The 440 uses the same STK style driver IC's most of their other MC series stuff uses, you probably have a bad one in there. Do you have a scope?
Perry - thank you contacted that guy to see if he still has a .pdf of the manual. Some guy on eBay has them for $30 if I get desperate.
I do have a scope, I have a Rygol DSO.
I do have a scope, I have a Rygol DSO.
Since you have a scope, look up the data sheet on the STK chips and see what the input and output pins are. Once you identify those play a sine wave through all the inputs in turn while reading the respective input and output pins on the STK. My guess is you will find all the inputs to the STK’s equal, but the output of the bad channels will be diminished. If that’s what you find, you’ll need replacement STK’s which are NLA. You can take your chances on eBay like I did, but of course there are no promises it will last since they are certainly all counterfeit. If you do replace them, I strongly advise adding some type of heatsink as they get quite hot in operation. I did this to my own amplifier, and it continues to work to this day.
Thanks
I am a little shocked to see multichannel IC's in an amp like this. McIntosh may be more marketing that substance unfortunately.
I would bet since there is still output that your advice is on he right track. I will mess around with it this week and confirm.
I was also able to get a copy of the service manual.
I am a little shocked to see multichannel IC's in an amp like this. McIntosh may be more marketing that substance unfortunately.
I would bet since there is still output that your advice is on he right track. I will mess around with it this week and confirm.
I was also able to get a copy of the service manual.