Hello all,
I have had this problem for a while now, when the amp is sitting idle, every once in awhile, I'll see the red LED blinking. It doesn't happen while it's being used. The amp board on that side is hotter than the other. Using a temp probe I have the location pointed at the Bridge rectifiers.
I noticed in the repair guide that the clipping LED is driven by Q1 & Q2 which activates the OP amp to overcome by delivering higher voltage to them, that extra voltage operates the clipping LED through the small bridge rectifier. It requires 2.6v to operate.
Could the Bridge rectifiers be bad or could it be the OP amp acting up and supplying voltage when it's not needed?
These amps have a long process for setting bias voltage and I checked by basically checking voltages on one of my other boards so that it was very close. (I checked it at the pot output) So I'm not sure if it's getting messed up after that or if it's even possible. That's why I turned my attention away from bias and since the rectifiers are hot, and the clipping LED circuit ties into them, it kinda looks like this could be the problem? The rectifiers are really cheap (unless I need a very specific type) manual says 25A 400V I do know there's 4 different types and I'm assuming the 3 line voltage is not used and the simple one might work? It's square with a hole in the center with 4 wires and I see they make them with spades too.
I'm leaning towards a bad op amp and I'll pick up the rectifiers as well while I'm doing it. I've already replaced the biggest capacitors because a few didn't like the heat, one had a tiny bulge but they all still tested fine.
The amp sounds great, with no noise (only the tiniest transformer hum if you put your ear close to the case but nothing from the speakers) so I haven't been that concerned.
The boards are very easy to work on and I'd like to get this done finally, been this way for 7 or more years, it it doesn't affect anything, even when the lights blinking, if I put on some music it plays fine and after a few songs the light stops blinking. So it's been a mystery. Both channels have the same output while playing. Imaging and stage are perfect with every centered.
I have 2 of these amps and one runs the woofers on a set of Martin Logan Aerius and the other runs the panels. I've bypassed the crossover and use an active crossover. I use the blinking amp for the woofers. I'll probably move each amp to a dedicated side, I just added the second amp again and removed the jumpers and ran the 2nd wires for testing and then remembered I need to resolve the LED thing again after not using the amp for a year.
Any advice would be helpful, it's not a big deal to do the work I would rather not be removing parts I don't need to just to save wear on the copper traces. The Rectifiers mount on the heat sink and are very easy to replace.
I have had this problem for a while now, when the amp is sitting idle, every once in awhile, I'll see the red LED blinking. It doesn't happen while it's being used. The amp board on that side is hotter than the other. Using a temp probe I have the location pointed at the Bridge rectifiers.
I noticed in the repair guide that the clipping LED is driven by Q1 & Q2 which activates the OP amp to overcome by delivering higher voltage to them, that extra voltage operates the clipping LED through the small bridge rectifier. It requires 2.6v to operate.
Could the Bridge rectifiers be bad or could it be the OP amp acting up and supplying voltage when it's not needed?
These amps have a long process for setting bias voltage and I checked by basically checking voltages on one of my other boards so that it was very close. (I checked it at the pot output) So I'm not sure if it's getting messed up after that or if it's even possible. That's why I turned my attention away from bias and since the rectifiers are hot, and the clipping LED circuit ties into them, it kinda looks like this could be the problem? The rectifiers are really cheap (unless I need a very specific type) manual says 25A 400V I do know there's 4 different types and I'm assuming the 3 line voltage is not used and the simple one might work? It's square with a hole in the center with 4 wires and I see they make them with spades too.
I'm leaning towards a bad op amp and I'll pick up the rectifiers as well while I'm doing it. I've already replaced the biggest capacitors because a few didn't like the heat, one had a tiny bulge but they all still tested fine.
The amp sounds great, with no noise (only the tiniest transformer hum if you put your ear close to the case but nothing from the speakers) so I haven't been that concerned.
The boards are very easy to work on and I'd like to get this done finally, been this way for 7 or more years, it it doesn't affect anything, even when the lights blinking, if I put on some music it plays fine and after a few songs the light stops blinking. So it's been a mystery. Both channels have the same output while playing. Imaging and stage are perfect with every centered.
I have 2 of these amps and one runs the woofers on a set of Martin Logan Aerius and the other runs the panels. I've bypassed the crossover and use an active crossover. I use the blinking amp for the woofers. I'll probably move each amp to a dedicated side, I just added the second amp again and removed the jumpers and ran the 2nd wires for testing and then remembered I need to resolve the LED thing again after not using the amp for a year.
Any advice would be helpful, it's not a big deal to do the work I would rather not be removing parts I don't need to just to save wear on the copper traces. The Rectifiers mount on the heat sink and are very easy to replace.
Last edited: