lp-2020a+ with no sound, no relay click, no nothing

leosep

Member
2013-01-10 5:01 pm
Hi all, I got this lepai lp-2020a+ from ebay, at first it worked ok but now no audio comes out from speakers, cant hear that click of the relay, no pop when powered, i opened the amp and tested with speakers bypassing the relay, capacitors, etc, but no nothing. Tested with various power suplies. also with one that i use with a lp-2020 model. The blue light is on. I waited with the amp powered on for more than 1 hour and nothing. Dont know what else to do. :confused:
 

Kyriarxos

Member
2010-01-05 2:43 pm
Sorry to hear that; similar story here:

Short version: Mine gave up too after several days of happy post-surgery performance, after having replaced everything upgradeable.

Long version: Four plus days of burn in, then burn out. Found it shut off and the chip looked ok, but smelled bad; the fuse on the regulated 13,8v psu was burnt too. After replacing the fuse, the psu was no longer regulated at 13,8 but at 2x (!) that voltage! I found out the hard way, when, after changing fuse, the lepai wouldn't start at all (no led, no nothing). So, I plugged it on an audiophonics 2020 board and its chip literally blew up with a spark and had a silicon piece burst out leaving a crater on it... Add another amp and a psu destroyed during lepai-troubleshooting. Then took the lepai to a Kingrex psu, causing it to have its fuse blown, indicating that something is terribly wrong in there. Verdict: Three healthy devices and the lepai itself (with man-hours of modding on it) gone in one evening. Frustration...

The only way to start it up now is with a non-regulated fuse-less wall wart. When this happens the relays never click, whereas the chip & heatsink go very hot very quickly - didn't leave it on for more than seconds. Please note that right after all modifications the thing was running much cooler than before, cold to the touch on the outer casing that is. Oh, and the sound!!!

Question (not that I'm not going to try it anyway and post back, with pics should it resurrect) would be whether this lepai -and maybe most failing ones- might work again if the chip is replaced. Maybe 13,8v constant is too much? What do you think?
 

ricortes

Member
2009-10-24 1:46 am
Well you did ask for input.

Ditch Lepai, forget the 2020. If you look in class D amps here, you will find plenty of problems with the chip and general design i.e. tone controls. Switch to a Sure 2024 if you want a nicely built amp for about the same money. I haven't looked on eBay lately for them because mine has been working faultlessly for almost 5 years now.

The Sure isn't quite as complete at the Lepai, no volume knobs or case, but they use better components that are there and build quality can't be compared. I'd rather have a Sure 2024 in a cheese box then a Lepai in an anodized aluminum case.
 
The 2020+ will protect itself from lo/hi voltage and speaker shorts. Try a known good regulated 12 volt power supply without any speakers connected to it and see if the relay kicks..

It will operate down to a voltage of ~9.5 volts but will go into self protection @~14.6 volts. (At least mine does)

Had one with a bad power switch. The LED's would come on but every time I put any audio to it, the amp would shut down. The switch was resistive. It allowed enough current to pass to fire the LED's but that was all. I just bypassed it..

Check some resistors. Maybe one is out of range. Good luck!
 

Kyriarxos

Member
2010-01-05 2:43 pm
Thanks for your input, even though I lagged a year!

I am (im)patiently waiting for a replacement chip right now, have already desoldered the failing one -did a neat job removing it too- so we are looking at 50-50% chances . I am a bit optimistic about this, although I also favor the 2024 and still have the legendary Sonic Impact slightly modified in my very small Tripath collection. Nevertheless I have to get this Lepai to work for the sake of confidence and time; it was initially bought to experiment with and after that it looked and sounded so good that I couldn't get rid of it anymore.

A properly laid out 2024 will perhaps be the next test-bed... The SI would take 13,8v constant for several months, so I figured out it would be safe for the Lepai too, maybe I was wrong, maybe there is something rotten inherently in this design as you suggest.

The tone controls were a actually a reason why I chose to experiment with it, I like fiddling with them and they can be of assistance once the opamps are changed to one's preferred kind. Yes, it would be compromised on dynamics, presence and transparency with the tone-sag in the way, but was so smooth, grain-free and relaxed that you could listen to it all day.
 

ricortes

Member
2009-10-24 1:46 am
Among other things, the Lepai left off some of the protection diodes. There should be a schematic floating around in D amps or T amps with them added. I vaguely recall some problem with the protection circuit too. Too long ago to remember but I thought its mute or function logic was inverted.

Someone else ran the Spice<?> simulations for the tone controls. They ended up replacing many of the parts. I'm guessing the work involved in doing all the component removal and replacement is greater then building tone controls from scratch.

Yes, nice amp when they are working right. I went through the original and one replacement 2020 before I got tired of working on it. Not enough circuit board left to replace it another time. The only way they could have made the circuit board worse is by laying copper traces on a cracker.