Aerius, low output, possibly hit by surge

[kevington118]

Hello, I'm a new member here. I've recently picked up a pair of Aerius speakers from someone who said that stopped working after being hit by a power surge. However, he was very vague about what exactly happened and didn't seem to have an electrical background so I'm trying to approach this repair with an open mind.

Started by searching Google, which led me to a few forums with people experiencing similar symptoms and finding various solutions. I tried vacuuming/showering the panels with no luck. I double checked all the terminations, all seemed to be secure. I removed the binding jumpers and fed signal to the woofer and panel separately, woofer output is comparable to the rest of my speakers while the panel is barely audible.

I removed all connections to the speakers and let them sit for a couple days. Then I opened the cabinets and visually checked over everything, no blown fuses, no burned resistors, no blown capacitors.

I then resorted to contacting ML customer service who gave me lots of diagrams and procedures for troubleshooting. The bias voltage check requires a 1 gig ohm resistor to prevent damage to the multimeter, so I'll be picking up one of those to perform that test next.

Is there anything else I can check in the meantime? Since opening the cabinet, I've checked all the components I can and nothing seems to be out of spec. Until I try the bias test, I'm stumped.

Any help or direction would be appreciated

 

[Tosh]

You can check that one winding of T1 is outputting ~160VAC.

 

[kevington118]

You can check that one winding of T1 is outputting ~160VAC.

Is that the same as this test? I found this in another forum and tried it, mine read about 260v on both speakers.

 

[Tosh]

Yes! What's a hundred volts between friends?

 

[kevington118]

Yes! What's a hundred volts between friends?

So that transformer doesn't seem to be the issue. I did the bias voltage test and did not get the 17-30 volts DC that I was supposed to. How often does the step up transformer go bad?

 

[Tosh]

T1 is the little PS transformer on the pcb. One half of T1 feeds the HV section directly, and the other half feeds the music sensor section and eventually switches on the Triac1 (and the main LED) which then completes the HV circuit. On mine the HV faded away slowly lowering the panel's output and acted as if the Triac or T1 was bad, and after knocking on it T1 went out permanently.

The big audio step-up transformer is very rugged....

 

[ttocs]

I then resorted to contacting ML customer service who gave me lots of diagrams and procedures for troubleshooting. The bias voltage check requires a 1 gig ohm resistor to prevent damage to the multimeter, so I'll be picking up one of those to perform that test next.

So that transformer doesn't seem to be the issue. I did the bias voltage test and did not get the 17-30 volts DC that I was supposed to. How often does the step up transformer go bad?

I did this same test with the same resistor a couple weeks ago. My power supply was outputting fluctuating millivolts. The speaker involved is the C18 Focus, only 1-1/2 years old. So I guess they can go any time.

Since being a ML customer for about 13 years and having purchased 22 or so products, this was the first failure. That's a great record!

 

[kevington118]

T1 is the little PS transformer on the pcb. One half of T1 feeds the HV section directly, and the other half feeds the music sensor section and eventually switches on the Triac1 (and the main LED) which then completes the HV circuit. On mine the HV faded away slowly lowering the panel's output and acted as if the Triac or T1 was bad, and after knocking on it T1 went out permanently.

The big audio step-up transformer is very rugged....

That might be it. The led does not illuminate even with signal. I just received the replacement hv transformer from customer service, so in the coming days I'll de-solder the old and re-solder the new.

 

[kevington118]

I did this same test with the same resistor a couple weeks ago. My power supply was outputting fluctuating millivolts. The speaker involved is the C18 Focus, only 1-1/2 years old. So I guess they can go any time.

Since being a ML customer for about 13 years and having purchased 22 or so products, this was the first failure. That's a great record!

So the fluctuating readings is normal? Did you fix your issue and if so, how?

I'm newer to Martin Logan products, but as an electrician I've been fascinated by the electrostat concept for years. I also own the Cinema center channel and Script surrounds and those have been flawless for about 3 years now.

I recently picked up the Aerius speakers locally, knowing that they had an issue, as it was documented by the previous owner. Hopefully I'll be able to restore them and have a fully electrostatic surround sound experience

 

[ttocs]

So the fluctuating readings is normal? Did you fix your issue and if so, how?

I'm newer to Martin Logan products, but as an electrician I've been fascinated by the electrostat concept for years. I also own the Cinema center channel and Script surrounds and those have been flawless for about 3 years now.

I recently picked up the Aerius speakers locally, knowing that they had an issue, as it was documented by the previous owner. Hopefully I'll be able to restore them and have a fully electrostatic surround sound experience

No, not normal. Got a replacement PS from ML, Faaaaast!! They're great! Installed it and right away got the expected voltage of 23.5V! So, all is well now.

 

[kevington118]

No, not normal. Got a replacement PS from ML, Faaaaast!! They're great! Installed it and right away got the expected voltage of 23.5V! So, all is well now.

Understood, so you replaced the entire power supply board correct, not just individual components?

 

[ttocs]

Understood, so you replaced the entire power supply board correct, not just individual components?

Correct. But on my speaker it's just multi-pin and single pin connectors that get pulled off the failed board and pushed back on the new board. No soldering.

 

[kevington118]

Correct. But on my speaker it's just multi-pin and single pin connectors that get pulled off the failed board and pushed back on the new board. No soldering.

That would make life much simpler indeed! I still replace just the transformer for now and see if that fixes the issue.

 

[Leporello]

If the LED is not illuminating that probably means your HV transformer is not necessarily at fault. The sensing circuit fires the triac, which bypasses R16 and gives you full bias supply. Otherwise, you're at reduced bias, for standby, which indeed would give you reduced output. The schematic doesn't show where everything goes, for example the bottom of the lower winding of T1 but presumably the Triac determines how much voltage is fed to the multiplier stack. You might check the quad op amp, IC1. If you're lucky, it's in a socket. There's a decent probability of it frying in a power surge. If it is socketed just swap it out. Otherwise you may want to determine what exactly in the sensing circuit isn't functioning. IC1 does a lot of things related to it.

 

[kevington118]

If the LED is not illuminating that probably means your HV transformer is not necessarily at fault. The sensing circuit fires the triac, which bypasses R16 and gives you full bias supply. Otherwise, you're at reduced bias, for standby, which indeed would give you reduced output. The schematic doesn't show where everything goes, for example the bottom of the lower winding of T1 but presumably the Triac determines how much voltage is fed to the multiplier stack. You might check the quad op amp, IC1. If you're lucky, it's in a socket. There's a decent probability of it frying in a power surge. If it is socketed just swap it out. Otherwise you may want to determine what exactly in the sensing circuit isn't functioning. IC1 does a lot of things related to it.

If this is what you're referring to, then yes I did try testing it but didn't get any steady readings.

 

[kevington118]

They did pry up with a little gentle effort. Boards have been disconnected for days so they're fully discharged. I ordered replacements from customer service and will report back with findings.

 

[Tosh]

The triac is simply connecting ground to the bottom of the diode/capacitor HV ladder, so if you short out the triac (which is what the MS would normally do), the HV ladder should energize...

 

[kevington118]

The new opamp arrived today. I installed it onto the board while still disconnected from everything, then I gave it 120v and a signal, and the led came right on. So I wired it back up to the cabinet, and that did the deed. Panel is back to life! I did not even try the new transformer because I never got around to desoldering the old one. So I dodged that bullet. Thank you for taking the time to help troubleshoot!

 

[Tosh]

Congrats! Do you have both working now?

 

[Robert D]

Man, we have some knowledgeable folks here! This board is great.