peterdulux
New Member
Looking at picking up a MX2 amp and was hoping for advice on what to look out for?
Any advice would be helpful.
Any advice would be helpful.
MX 2 question
- Thread starter peterdulux
- Start date
Broken HCA (BA3122N)
LOL.
http://www.audiokarma.org/forums/index.php?threads/yamaha-mx-2-stereo-amplifier-hca-chip.859286/
LOL.
http://www.audiokarma.org/forums/index.php?threads/yamaha-mx-2-stereo-amplifier-hca-chip.859286/
bmanone
Active Member
If you buy a unit that plays both channels, both HCA chips should be fine, if you buy a non playing unit all bets are off. I'm not sure what caused the failure in my MX-2, I suspect one of the following: transistor failure in the V-Amp; transistor failure in the A-Amp; failed solder joint in A-Amp or V-Amp; or premature failure of HCA IC (BA3122N). My gut feeling is that HCA IC did not fail without an external cause.
My advice if you get a working unit that hasn't been serviced is that you get it serviced before regular use.
Something that I found when servicing my MX-1 that is probably applicable to the MX-2 for what it's worth:
The output transistors (and their boards along with them) are mounted to a rectangular aluminum bar, which is then screwed to the main heat sink. What I found when I removed the transistors/boards/bar from the main heat sink is that they were barely attached.
The screws that go through the bar were so short that they only had 1 thread of bite in the heat sink and were mostly little more than finger tight (the last 2 threads are tapered so there is less actual contact than it looks at first glance). There was so little pull that the heat conducting paste had never even been pressed completely flat between the aluminum. I don't think that the amp was ever getting cooled correctly.
I found some screws that were about 3mm longer and used them, along with some new paste. It gave at least 4 threads of bite and pulled things together nice and tight.
Cheers,
James
The output transistors (and their boards along with them) are mounted to a rectangular aluminum bar, which is then screwed to the main heat sink. What I found when I removed the transistors/boards/bar from the main heat sink is that they were barely attached.
The screws that go through the bar were so short that they only had 1 thread of bite in the heat sink and were mostly little more than finger tight (the last 2 threads are tapered so there is less actual contact than it looks at first glance). There was so little pull that the heat conducting paste had never even been pressed completely flat between the aluminum. I don't think that the amp was ever getting cooled correctly.
I found some screws that were about 3mm longer and used them, along with some new paste. It gave at least 4 threads of bite and pulled things together nice and tight.
Cheers,
James
