XPA-2 Turn-on Fault, Power lite Blinks

[Priapulus]

I have an older XPA-2 Amplifier, with a linear power supply. It normally lives on standby, and switches on automatically via the enable wire from the XMC-2.

Sometimes, instead of coming on, the power light just blinks on and off (about once per second). Each times it blinks, I can hear relay(s?) switching on-off. After a half dozen tries, it comes on normally and sounds great. I presume it is failing a power-on-test. 

It's out of warranty, and there is the scary cost of freight (I don't live in the USA). I can solder, and know how to test capacitors, etc. So thought I'd take a look under the hood, before I send it back.

Any suggestions or advice? 

Sincerely,
/b

[ttocs]

Aged capacitors in the power supply?

[cawgijoe]

I would check with Emotiva first to what it would actually cost you to send it in for check and repair. I know they have a set repair amount.

After you receive that cost information, then you can decide whether to have them look at it or tinker yourself.

Also, if you decide to tinker, see if they can provide you schematics.

[vcautokid]

I is about that time. Also not just the power supply caps, but the other ones too especially for the micro controller. Once that controller gives up. That XPA will no longer function at all.

[Priapulus]

Aug 7, 2023 10:22:01 GMT -5 vcautokid said:

I is about that time. Also not just the power supply caps, but the other ones too especially for the micro controller. Once that controller gives up. That XPA will no longer function at all.

That the power light blinks, suggests to me that the microprocessor is working, and is seeing something it doesn't like... But if I have to open it, I'll replace ~all~ the caps with high quality ones.
/b

[AudioHTIT]

Have you tried it without anything connected? No inputs or outputs? This would eliminate some kind of speaker / cable issue the amp doesn’t like, or possibly some kind of errant signal coming to the inputs.

[leonski]

Aug 7, 2023 9:27:06 GMT -5 ttocs said:

Aged capacitors in the power supply?

When 'popping the hood'.....the big PS capacitors will be easy to tell BY EYE if they are bad.
Leaking?   Bulging?  are the 2 big hitters here.   If any are bad, replace them ALL.....No prisoners.   
Nelson Pass said that such caps should go 30 years with regular use.    It's when they dry out due to disuse that problems happen.

If you replace them?   'just because'?    Use only TIER 1 PARTS.    Elna?   Rubicon?     Nichicon?     Panasonic?    Vishay?    
Don't get tricky here.    Replace with exact value if possible AND the same tempreture rating......

Could be a relay not 'latching' in the on position.    If they are socketed (probably NOT!) it is easy to swap 'em......IF you can find them at all.

First step?  

D|ISCONNECT everthing from amp.   Speakers and Inputs.    Try it THAN.     If it passes that test?    Add stuff back ONE at a time trying to 
find what is causing fault.....

Certain parts, like transistors, can be checked with COLD AIR     When running, a short spritz of 'cold' may cause failure or change of state.

Proper troubleshooting should becoma a habit.....with a built-in mental checklist.....

[audiobill]

Ten years old, replace caps?

Way too soon.

[leonski]

Many years ago, NAD had problems and really suffered a reputation 'hit' as a result.

Me? I've got ELNA caps in the PS of my 40+ year old Kenwood KA7100 which are still FINE......

www.diyaudio.com/community/threads/capacitor-question-nad-c272.341016/

[emotimmo]

Have you tried turning on the am without the use of the trigger cable?

[leonski]

Aug 15, 2023 10:45:48 GMT -5 emotimmo said:

Have you tried turning on the am without the use of the trigger cable?

See my post.....2 or 3 above......where I mention a good scheme to begin troubleshooting.

Sure.....FIRST unplug everthing.     

[speedydave]

Aug 7, 2023 9:22:29 GMT -5 Priapulus said:

I have an older XPA-2 Amplifier, with a linear power supply. It normally lives on standby, and switches on automatically via the enable wire from the XMC-2.

Sometimes, instead of coming on, the power light just blinks on and off (about once per second). 

Any suggestions or advice? 

Sincerely,
/b

Just been thru this exact issue, and with many hours of tracing the circuit boards and figuring out just how these things work,  I have solved the issue ( at least in mine )

I reached out to  service@Emotiva  and they supplied the technical knowledge that helped me understand the various circuits and ultimately rectify the fault.

A big thanks to Joe Sr.  !!!!


*****************************************                   my issue was a faulty -38v connection to one of the amplifier boards.                           ****************************

Caution, technical stuff ahead !


Firstly, there is a small "standby" transformer that powers the "Micro" and soft start relay board whenever the amp is plugged in and the power switch on the rear panel is on.

The relays you hear "clicking" are the two "soft start" relays engaging to supply AC power to the MAIN power transformer, which powers the amplifier boards, when you push the power button on the front panel.
That switch just sends a 5 volt signal to the "micro" to start the power up sequence.  The power up sequence also powers up the "protection" circuit and if it doesn't pass the tests, it tells the micro to shut down power. (relays turn off )

On each power amp board, there is a dedicated "protection" chip, a UPC1237, which you can google to get the spec sheet.

It has the ability to detect DC voltage (which is bad) on the amplifier outputs ( to the speakers)
It has the ability to detect an AC voltage so that it can disconnect the speaker relay when the power turns off ( stops power off thump ) but the XPS-2 gen 1 does not have speaker protect relays. ( but it still uses this AC input ! )
It has the ability to detect overload (clipping).
It has the ability to detect overheating of the main heat-sinks.

If the chip detects any of these faults ( that it has been configured to detect ) it sends a signal to the "micro" to kill the main power relays, removing the main power from the amps to help protect them.

So what is happening with yours, is that the protection circuit is triggering after the main power up sequence,  which then tells the micro to turn off the power on relays ( the click )

This is where it gets tricky.
You need the amp to fully power up to be able to test various circuits, but the amp powers down before you can do any test !

STOP RIGHT HERE IF YOU DON'T KNOW WHAT YOU ARE DOING !!   BAD THINGS CAN HAPPEN !!!!

Not sure this is the place to go into all the details publicly. as I mentioned, if you are not trained, this "unprotected testing" can get very dangerous !!

You can message me ......

[leonski]

Excellent post. And a 'Fair Warning' about safety / training / troubleshooting........

We had stickers in some VERY high voltage gear (100kv to 160kv typical) that said 'Death Is Final'.......and finished the warning.

And if you DO continue....you CAN make things worse.