Should I buy: Mcintosh 754 with one bad channel
- Thread starter tdwpgtp
- Start date
Worked over a couple of those, but never lived with either type Mac power here. I liked the pair of 75 better than the 240, but wouldn't have turned it down to try here.
No need for apologies. What you said is what many people need to hear when fixing, well, just about anything. There is no problem with learning, but it is best to do so on cheaper stuff, rather than mess up something fairly valuable, collectible, or desirable. I don't want to be one of those guys who botches a fairly straight forward repair, simply out of ignorance, inexperience, or in the name of being cheap.
As for people's impression of sound, I do not take other's opinions for gospel, but it is reassuring to hear that a majority of people do or do not like a given item that I am taking a relatively large (to me) risk on. That said, I have some pretty cheap gear that I personally enjoy that many other probably would consider junk.
See above. I do place some value in other's opinions, but I do not blindly follow them. In this case, I want to make sure that I have an out, in the event that I do not want to keep it, without losing any money. You see, the way I justify my addiction to the wife is that I only buy what I can sell for more. She can't argue with it if I'm not losing money!
damacman
Resident Psycho
I'd wager a Ben Franklin that I could set up an A/B/X test between the MC754 and say an original MC240 and your ears could not detect the difference.
damacman
Resident Psycho
Did you buy it?No need for apologies. What you said is what many people need to hear when fixing, well, just about anything. There is no problem with learning, but it is best to do so on cheaper stuff, rather than mess up something fairly valuable, collectible, or desirable. I don't want to be one of those guys who botches a fairly straight forward repair, simply out of ignorance, inexperience, or in the name of being cheap.
As for people's impression of sound, I do not take other's opinions for gospel, but it is reassuring to hear that a majority of people do or do not like a given item that I am taking a relatively large (to me) risk on. That said, I have some pretty cheap gear that I personally enjoy that many other probably would consider junk.
See above. I do place some value in other's opinions, but I do not blindly follow them. In this case, I want to make sure that I have an out, in the event that I do not want to keep it, without losing any money. You see, the way I justify my addiction to the wife is that I only buy what I can sell for more. She can't argue with it if I'm not losing money!
No need for apologies. What you said is what many people need to hear when fixing, well, just about anything. There is no problem with learning, but it is best to do so on cheaper stuff, rather than mess up something fairly valuable, collectible, or desirable. I don't want to be one of those guys who botches a fairly straight forward repair, simply out of ignorance, inexperience, or in the name of being cheap.
As for people's impression of sound, I do not take other's opinions for gospel, but it is reassuring to hear that a majority of people do or do not like a given item that I am taking a relatively large (to me) risk on. That said, I have some pretty cheap gear that I personally enjoy that many other probably would consider junk.
See above. I do place some value in other's opinions, but I do not blindly follow them. In this case, I want to make sure that I have an out, in the event that I do not want to keep it, without losing any money. You see, the way I justify my addiction to the wife is that I only buy what I can sell for more. She can't argue with it if I'm not losing money!
When it comes to my wife; these are the words I live by: "it's easier to ask for forgiveness rather than ask for permission"
I've heard that many times before, but it seems she gets more upset when I don't tell her first. Like I said, as long as I am breaking even or better in the end, she's happy. It sort of makes the whole hobby more of a treasure hunt, anyway, and makes it more fun.
@damacman I am going to check it out after work today
Glad you decided to pull the trigger. My money says it's something simple. Good luck.
Looks like a burnt transistor on one of the driver boards. I've attached a couple pictures. Would these be the cause, or a symptom? As in, what would have caused it to burn? Is something upstream likely bad, or could it have just been over driven? I will be taking the board into work tomorrow to look at it with our EE. Hopefully it is just this transistor, as that is an easy fix.
But wait! There's more! The power transistors (I think) were replaced at some point, one of which has a lifted and (maybe) repaired trace, shown in the second picture. Then there are several transistors that look like they've been mashed down, one of which has a broken leg, shown in the 3rd picture.
DOBIEGUY
Well-Known Member
Unfortunately for the OP this appears to be an ugly situation. Obviously someone has been inside.
Anyones guess what type of repair was attempted. Approaching thirty years old any number of issues could haved caused this. Or maybe just outright abuse.
Everyone likes the 'it just needed a new fuse' outcome. Not with this.
My money says the repair could cost twice the purchase price.
Good luck
I am capable of replacing the components themselves.. However, identifying any components that are not obviously damaged will be a bit out of my abilities. I will be consulting those smarter than I, and in a worst case, I may find and buy a replacement board. The cost of the components will be low, and my labor is "free".
I will compare this board against its twin tonight to see if the other has had similar repairs done. It is possible that during the repair they crushed the small group of transistors, did not notice, and simply gave up when it would not work. I don't ' know, but at this point I'm not tapping out, yet.
I will compare this board against its twin tonight to see if the other has had similar repairs done. It is possible that during the repair they crushed the small group of transistors, did not notice, and simply gave up when it would not work. I don't ' know, but at this point I'm not tapping out, yet.
OMGCat!
Super Member
I'd made sure that the replacement transistors are what is supposed to be in there rather than a sorta good sub. When you compare with the working board you can write the proper numbers down. Once you know what should be there you can look for proper sub recommendations here.
I'd say it likely shorted an output and worked it's way down stream which is why that small signal device got it's leg melted off. If you're doing the work and have an EE buddy helping you out it shouldn't cost much to get going again.
I'd say it likely shorted an output and worked it's way down stream which is why that small signal device got it's leg melted off. If you're doing the work and have an EE buddy helping you out it shouldn't cost much to get going again.
