Martin Logan Aerius i strange problem


2019-10-02 1:04 pm
Hello all, this is my first post here. Nice to be part of the community!

I have recenlly bought a pair of Aerius i and one of the speakers has a strange problem. When i start playing music the panel is buzzing/ pop pop besides the music played. Allso the red LED on that speaker does not light up(it is good i checked). Both panels are ok, i cleand them and swiched between. The problem remains with the same speaker.

Has anyone encountered this problem or does anyone have the shematics for the main board?

Thank you, John.
Based on your description, you may have one or more problems. Probably the easiest thing to do is to first divide the speaker into sections and isolate which section is causing the buz/pop problem. Once that is fixed, the power LED may work properly, or there may be additional issues to track down on the HV supply board.

Find attached the overall circuit diagram for the Aerius i. I sectioned off the circuit into 5 main blocks. If I understand your post correctly, you already swapped the panels between speakers and both panels work fine, the buz/pop noises stayed with the base of the speaker where the rest of the electronics are. So, section 1 can be checked off as good.

Considering that in addition to the buzz/pop noises the power LED isn’t work, I would think the next likely culprit would be item 2, the HV power supply board. As seen in the attached pic there are just a few terminal blocks connecting to the board, no un-soldering required, so pretty quick and easy to swap between speakers. There are a few slightly different versions of the board that were used over the years, so be sure to take a pic of wiring beforehand as a reference for what wires go where. See if the buz/pop follows the board. If it does, we can then tackle isolating the problem on the board.

If the HV boards wasn’t the problem, the next thing I would check is item 4, the limiter. Attached pic shows what it should look like…or similar. To check, just disconnect one of the wires from the terminal block and see if the noise problems go away.

The usual culprit is the HV board, but let us know what you find out.


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2019-10-02 1:04 pm
Thank you for the schematics! I managed to get rid of the poping/buzzing by washing the panels and what a difference in sound that make !
Now both speakers sound great, no additionat noise. The only thing left is the red LED that still does not want to come on. For sure is from the HV board. I will search further.

P.s. I allso did an upgrade to the bass filter. Bypassed both capacitors from notch filter and the one in parallel with the bass driver with 2.2uF nonpolarised Audiophiler capacitors. An upgrade will come to the tweeter filter also, bypass with 0.01uF Vishay.
… I managed to get rid of the poping/buzzing by washing the panels …
Glad to hear a good cleaning has solved the buz/pop problems. :up:
I thought you were saying that when swapping, both panels were fine but the problem persisted for one of the speakers.

… The only thing left is the red LED that still does not want to come on. For sure is from the HV board...
Does the LED on the HV board come on but the front panel one doesn’t? Or do neither illuminate.
As you can see from the schematic, resistor R30 is the only circuit component between the auto-ON signal from pin 8 of the op-amp and the LED. It is possible that a previous owner may have accidently swapped the wires at the terminal block. You might try measuring the voltage at the terminal block when powered on and/or swapping the LED wires.


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It has been a couple of years but I think it was a problem with the music sense circuit in one speaker. I would have to turn the volume up quite high to get the power supply to switch on. When I checked the capacitors on the power supply board one had very high ESR. I used to have some pictures but think I lost them when I got a new computer. I have a high voltage schematic. Not sure it is exactly for the Aerius but it was near enough that I was able to troubleshoot the circuit.
Good luck,


2019-10-02 1:04 pm
I replaced all the capacitor from the crossovers and carefully analysing the sound afterwards i noticed that the speaker that makes problems also sounds little bit dull, you have to carefully listen to notice the difference. I just ordered new capacitor for the power board as i saw that two of 100uF 10v are on the Music Sens path. I will replace all of them hopefully this to be the problem.


2019-10-02 1:04 pm
As i said. I replaced all the capacitors on the power board with audio grade Nichicon Fine Gold and Nichicon Muse. The difference in sound is BIG! Everithing is much clear, natural and lots of details came up much present.

Still the LED does not want to light up. I changed the boards from one speaker to another and the problem stais to same one. Allso that pannel sound slighly different. Same DB spl but veeerry little different. Some times you don't even notice.


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Is it possible that if one of the pannels is not working well , the red LED of signal sense not to come on?

You have been talking about the red LED on the front panel, which doesn't give any indication of HV supply function. But, if the red LED on the HV board does not illuminate, this would indicate that the HV supply is not getting turned on. So it could be related to a low output panel.

Look at the schematic back in Post #6.
The red LED on the front of the speaker is driven from the same signal as what powers the red LED on the HV board. The LED on the HV board must illuminate for the TRIAC to turn on and supply power to the HV multiplier. The red LED on the front of the speaker doesn't even need to be hooked up for the speaker to work properly.

With speakers powered up and front LED wiring hooked up to the terminal block, measure the DC voltage at the terminal block. It should be in the 1.5 - 2.2 volt range for a red LED. If it is closer to 15V, then the wiring to the front panel LED is open somewhere. If it is close to 0V, then there is a short in the wiring.


2019-10-02 1:04 pm
I will make the masurements for the front LED. The red ones from the HV board both of them light up.
The problem is that even when i changed the complete back of the speakers between them, it still did not want to light up(front LED).
In this few weeks i have the speakers it came one two times at half intensity.

Is there a way to measure the pannel?

Thank you.
…Is there a way to measure the pannel?
Are you having issues with the panel that had been noisy before you washed it? Perhaps lower output?
There isn’t much you can measure on the panels other than if they have developed leakage paths that are pulling down the HV bias. You might try adding a neon lamp leakage indicator in series with the diaphragm contact to see if the panel is leaky. See links below for details.

The rebuild of an old Audiostatic ESH100
ESL technical questions