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Diagnosing a 12V trigger problem between preamp and power amp
I'm gonna put this before the collective mind of the board since I'm just getting the cold shoulder from Emotiva. I have a new in October BasX PT2 Preamp and BasX 2 power amp. They are in a closed front cabinet, so a trigger from the remote controlled preamp to the power amp saves a lot of hassle each time I have a listening session.
Back in November I started having issues with the amp shutting down out of the blue. This is NOT circuit protection, It would just shut down. Often it would come back on with no intervention after 30 seconds to 3-4 minutes. After a few weeks of this and my first fruitless call to Emotiva, I just removed the trigger cable and ran the ON-OFF manually just to be sure the amp had no issues. It ran flawlessly.
After the holidays I went back to the trigger arrangement and lo and behold, the amp won't turn on at all. Hit the power button and it will eventually shut down on it's own, but NEVER turn on again.
This problem started out somewhat source dependent. When my Smart TV or FM were the sources, it was far more likely to malfunction. Vinyl or CD didn't have issues.
So can anyone tell me if there is an easy way to tell if the problem is with the PREAMP (sending 12V) or the AMP (receiving 12V)? Any contributions here are better than the manufacturer will give me, so TIA.
Comments
I'm not an electronics wiz, but put a scope on the trigger line. You can get them cheap on Aliexpress. That's way bad news to hear about Emotiva's lcak of support.
Interesting.. if it is just 12v rather than a lower voltage signal I wonder if it would simply be powering the coil on a relay.
That's how I think they work.
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If that is the case I suspect a failing cap attached to the relay. The intermittent power off issue experienced may be the dielectric breaking down inside the cap from heat, causing it to short and draw power away from the relay coil. After some time everything cools down due to no power and the cap stops shorting enough to allow the relay to trip again. Eventially the cap gets bad enough the circuit doesn't work anymore until the cap is replaced.
It seems failing caps in the power supply control is not uncommon for Emotiva. https://stereonet.com/forums/topic/123327-help-debugging-emotiva-8100-amp-inconsistent-powerup/
The output is the only thing that is really standard, 12v on 0v off. You should be able to measure this with a DMM.
What you described sounds like a failing cap on the supply side but that's a guess, it could just as easily be a cracked solder joint.
Chances are reading the output it will read 12v even in the failed state as there is no load, if your DMM has LOW Z, try reading the voltage on the LOW Z setting to simulate a small load. I would leave it on LOW Z for a long time to test for circuit integrity.
You could also isolate which side failed by grabbing a 12v trigger from a different device.
I would wager there’s some type of circuit in the amp that drives the relay. Smart engineers might even use a device as an isolator to avoid ground loops. Could be a flaky solder joint, bad cap or even a transistor that’s on the edge for that circuit.
This certainly seems to fit the scenario of creeping worse over time. And I believe it would tend to point at the problem being in the amp, rather than the preamp, no?
I may try to check the signal coming from the preamp at the plug jack with a multimeter, but no way am I opening anything only 3 months from new. Priority for now is determining which component is problematic.
I found a pic of the amp internals on their site. That looks like a small switch mode supply just for the turn-on circuitry.
Interesting note on the toggle: The two possible positions are "ON" and "AUTO-ON". The manual never really explains which does what. In my last correspondence with Emotiva they recomended I try turning it to "OFF". Sure, dude. Which "OFF"?
UPDATE: I appears that the problem has been solved. I've put several hours of listening in without any malfunction so I think it's good.
The problem was apparently a bad trigger cable coupled with using the incorrect toggle position. Luckily both the preamp and amp included a cable, so I had a spare to fall back on. I'll be hitting the market for a better quality 1 meter 3.5mm mono plug cable though.
Bottom line: I'm still EXTREMELY disappointed that between me and two Customer Service "engineers" it took 6 weeks to try checking the cable. It's also highly disappointing that between the owner's manual and the CS exchanges I still have no idea what the difference is between the "ON" and "AUTO" trigger toggle positions. I've contributed to enough tech support docs to know that Emotiva's is pretty shitty.