Portable Amp died on me twice ;-( Please help with diagnostics

[Wotan1]

This is to much to handle. The amp died on me twice and history repeated itself 100%. It's a portable amp with a rechargable battery pack included (inside)

Same history both times

Recieved amp (according to supplier battery pack inside was fully charged, with the capacity of 50 hours fulltime listening). Sounded great out of the box. I was not using a power supply. Listened for an hour and shut down the amp. Wanted to listen again a couple of hours later. I plugged the HP plug in the amp. When I pushed the power button the led started shining for a second and then died. So I suspected that the batteries were empty.
I went out the buy a PSU, within specs of supplier (24v, regulated, 500mA center positive plugs) Made sure center was connected to the +. Also had the adapter checked by an eletronics specialist for voltage. It measured 23.7V. Installed the adapter. Pushed the switch, got a led light for .1 second and then nothing.

Had to return the amp. According to service the primary electrolytic capacitors in the amp were blown. Amp was repaired and returned.

And then the history discribed above happened exactly the same. With the difference that
1) I bought a new PSU recommended by an headfier (an Ansmann).
2) heard some static noice when connecting the HP jack to the amp (switched off)
3) Noticed some sparkels when I connected the connector of the power supply to the amp (amp was already dead at that time, but I hope it could be rivived)

I checked and doubble checked the voltage and polarity before hitting the switch. Got a led for .01 second and then nothing..

So
> why did the amp stopped working at the 2nd round of listening. Batteries were fully charged and should have run for an other 48 hours or so. PSU was not used yet.
> Why the static when plugging in the HP's with amp of
> Are the adaptors playing a roll here or did the amp already died at the 2nd round of listening.
> What about the sparkels when connecting the addapter to the amp.
> I also heard some pulsing sound at one time when listning and hoping the amp would live again. The led in the PSU was pulsing as well.

The supplier has no idea. They personally tested the amp at 26.5 volts as 27 volts is the max recommended. So they do not know why it did survive this voltage for days yet die with 23v. So they blame it on the voltage or polarity. But what are the changes. Two different adapters both measured by an expert having resp 23,7 and 23.8v (in the last case I started with 20V).

Any suggestions on what could have happened are very much appreciated.

PS: Please note that this is a very good amp. I'm the only one having this issue. All users are very happy with the product and from what I have heard I would recommend this amp to everyone.

[Wotan1]

Your diagnostics are very welcome!!

[JLai]

Might help if you tell us what amp this is...

Edit: nvm...just checked the LISA III thread.

[kramer5150]

What kind of amp is it?

Does the amp by any chance require an AC power supply?

The EC/SS and earmax amps require an AC P/S, as does my entech DAC... for example.

[Wotan1]

Originally Posted by kramer5150

What kind of amp is it?

Does the amp by any chance require an AC power supply?

The EC/SS and earmax amps require an AC P/S, as does my entech DAC... for example.

This one is recommended by Triadadio for the Lisa www.triadaudio.net

http://www.alliedelec.com/Images/Pro...ts_8790090.pdf It says 2,5-140.4 WATT AC. (please note tha Triad advised 20-24 and that amp can take max 27volt.

The Ansmann PSU i used says: 100-240 AC and 12-24 VOLT DC

Please advise.

Thanks

[unbiased]

If the amp blew out using just the supplied batteries installed by the manufacturer, then the amp is defective. If the amp blew out only whenever you plugged your power supply into it, then there is something wrong with that power supply. Blown capacitors usually are indication that the voltage supplied was way too high or that you connected it with reverse polarity. These are the only two reasons for what you describe short of total bad QC on the part of the maker. I would think for a product like the LISA III that they would have reverse polarity protection so that it won't harm the unit if someone did plug it into reverse power supply connected. Anyway, is the manufacturer going to fix this for you again under warranty? Also if you have to send it in, I would recommend you send your power supply that you used so that they can verify if it is correct or not. This may reveal a mistake on your end though and thus they may void your warranty. Good Luck!

[kramer5150]

Originally Posted by Wotan1

This one is recommended by Triadadio for the Lisa www.triadaudio.net

http://www.alliedelec.com/Images/Pro...ts_8790090.pdf It says 2,5-140.4 WATT AC. (please note that Triad advised 20-24 and that amp can take max 27volt.

The Ansmann PSU i used says: 100-240 AC and 12-24 VOLT DC

If I read the above correctly, Triad recommends an AC power supply.

The Ansmann unit you used is a DC power supply.

You can't inter-mix AC with DC (although I've never actually dared to try).

[TzeYang]

AC Power Supply as in AC input DC output power supply i'm definitely sure.

There is no rectifier circuits or anything like it in the LISA III. It will not take AC.

[unbiased]

Originally Posted by kramer5150

If I read the above correctly, Triad recommends an AC power supply.

The Ansmann unit you used is a DC power supply.

You can't inter-mix AC with DC (although I've never actually dared to try).

Even if the LISA III was/is supposed to take an AC voltage supply, connecting your DC supply should not harm it one bit. I still think that your power supply voltage is reversed and that's why the capacitors were blown (or exploded). I know you said you measured the voltage and polarity of the plug but maybe your voltmeter leads could have been reversed and giving you opposite +/- readings? I've had this happen to me on the bench a few times during my life time fixing and measuring electronic gear! Some multimeters have their wire leads where you can plug the red + lead into the minus - lead of the meter and the black minus - lead into the positive + jack. If this was the case you would have been reading minus as plus and plus as minus! Also depending on what meter was used, some have a polarity switch to reverse the polarity readings. If you have this type of meter, then make sure the switch is in the positive position or that will give you opposite readings also. But plugging in a 24v DC into the unit if it was designed for 24v AC input, would not harm the unit. Plugging in an AC voltage into a DC input device that does not have reverse polarity protection, might do damage though. Check your multimeter.

[Negatron]

It would not be the first time a manufacturer got stuck with sub-standard, re-branded or failed grey market caps from a reputable supplier. It happens, they do fine with static testing but fail in the field. You should contact Triad, yours may not be the first they have heard of with the problem.