Lepai T-Amp with TA2020

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Just checked all the connections.. These are the results..

pin no 25 - +9v

pin no 2 - 0v

I didn't manage to find any short circuit..however I noticed 1 blue led is not working ..

What should i do now? If possible can someone please post the list of minimum equipment's I need to run this lepai as a power amp..(without preamp & this will make the circuit more simple & easy to diagnose)....Thanks
 
I'm suspecting something to do with the resistors & caps..

I already checked the power supply...It's more than enough to feed the amp..

What I've noticed is that some of the resistors & caps are not showing their correct value..(using multimeter) I'm not sure whether I can replace them since they are so small & not easy to find here..There was a short circuit earlier & probably this cause all these problems.. If you can please tell me the parts need to run just the ta2020 chip..(thisway i can identify which parts are necessary which are not). Thank you very much..
 
You can follow the diagram that I've posted before http://www.e-ele.net/DataSheet/TA2020.pdf on the page 5 appears the minimum components needed, DH are not needed if <13.5v

BTW the Lepai setup only differs on the op-amp section, and the protection circuit.

If you only have 9v at pin 25 something is wrong, because on mine at least, there is a direct connection from power supply line (after the big cap) to switch and then to pin 25.
 
Those are very interesting toroids! I didn't know about them. I think Ill try the ones that helder electronics sells first though. Although... these may be much easier to mount on the under side of the board, as opposed to trying to squeeze them in on the upper side of the board.

Thanks for posting these, where did you get them?
 
Just checked all the connections & i noticed something was wrong with the relay.. (Not 100% sure)

All the power input pins are receiving correct voltage (pin 22 ,25 ,27)

So is it possible to remove or bypass this relay ? (if I'm not wrong its not a must to run this amp)

By the way how to check those tiny caps using the multimeter ?

Thanks..
 
Check your power supply. I had 12VDC rated psu that would just blink your leds but not turn the relay on while other much tiny 10vdc rated psu's would just do the job.

My advice now is to save on parts and just go for the arjen helder ta2020. The MK II without mods is so much better than the modded lepai and costs only $ 10 more. I've sold all my lepais. MKll Version Tripath TA2020 PCB 25w CLass-T amplifier
 
@Virpz Lepai now is too expensive on ebay, but I've seen it for 10$ months ago (for that price is a great value, for the 20$ that could cost now is only a low cost option). The Helder MKII seems a great board, but you'll need a case, a potentiometer for volume, and some input and output connectors, that can easily increase the price...

Just checked all the connections & i noticed something was wrong with the relay.. (Not 100% sure)

All the power input pins are receiving correct voltage (pin 22 ,25 ,27)

So is it possible to remove or bypass this relay ? (if I'm not wrong its not a must to run this amp)

By the way how to check those tiny caps using the multimeter ?

Thanks..
You can bypass the relay, simply join the corresponding tracks on the bottom side of the PCB you can see that the relay simply disconnects/connects the negative from speakers. But I don't think that the relay could be the cause... 9v on the 22,25,27 is not a good sign if your power supply is 12v, clearly it doesn't have enough current to start the amp, and it's voltage falls.


Hello all. I', really interested in this small amp. But all the 105 pages of info, discussion and mods are a bit to much.
I created a wiki entry for this amp: Amplifier:Lepai T Amp - diyAudio (it is waiting for a moderator to approve it).
If it is approved it would be a great place to put all the filtered information.

What do you guys think?

Its a great idea. I have a lot of urls pointing to interesting mods, info, etc. will try to contribute ;)
 
Thanks for your reply..

I've already spent so much money & time for this circuit & I don't want to give up at this moment... By the way how can i know whether relay is working or not? (Newbie to this field)One blue LED is not receiving voltage as well...I'm thinking of replacing all the caps and resisters..This will cost me around $1 ..Its much cheaper for me..After going through the chip manual, now I can understand the circuit much better..My only worry is about those small SMD's.. It's difficult to find those stuff here & take some effort to solder..
 
Thanks for your reply..

I've already spent so much money & time for this circuit & I don't want to give up at this moment... By the way how can i know whether relay is working or not? (Newbie to this field)One blue LED is not receiving voltage as well...I'm thinking of replacing all the caps and resisters..This will cost me around $1 ..Its much cheaper for me..After going through the chip manual, now I can understand the circuit much better..My only worry is about those small SMD's.. It's difficult to find those stuff here & take some effort to solder..

As far as I remember you have the LP-2020B model, that is like the one I have, and has many of the components in SMD under the PCB. I wouldn't recommend to change all of them, as would be very hard and probably will lead to other problems...

What you should do is to check the voltages, on the PSU disconnected from the amp, on the amp once connected, on the relay pins (it has six pins, 4 of them in one side, and two on the other, these two are the ones that should have 12v to turn on the relay).

You can try to check the relay, but I don't think that this could be the problem... what the LP-2020B has is a DPST relay File:Relay symbols.svg - Wikipedia, the free encyclopedia the solenoid two pins are the ones mentioned before, and the 4 pins on the other side connect negative from chip with negative to speaker. What could cause a relay to stop working is, a broken solenoid (will have 0 ohm resistance if its shorted, or infinite if its broken) or broken switch contacts (but in this case you should hear de "click").
 
Those are very interesting toroids! I didn't know about them. I think Ill try the ones that helder electronics sells first though. Although... these may be much easier to mount on the under side of the board, as opposed to trying to squeeze them in on the upper side of the board.

Thanks for posting these, where did you get them?


I searched for these toroids on the site of my electronics shop : SEGOR-electronics GmbH, Berlin

The names they posted there were WEPD4L / SMSL1305 / PISM 100uH (three different manufacturers)

like here Fastron SMD Hochstrom Induktivität Serie PISR 1.3 A im Conrad Online Shop

It is easy to mount these, you only have to scratch away a little bit of the silkscreen (green stuff). Then solder it there, to remove it is a little bit trickier ;-)
 
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As far as I remember you have the LP-2020B model, that is like the one I have, and has many of the components in SMD under the PCB. I wouldn't recommend to change all of them, as would be very hard and probably will lead to other problems...

What you should do is to check the voltages, on the PSU disconnected from the amp, on the amp once connected, on the relay pins (it has six pins, 4 of them in one side, and two on the other, these two are the ones that should have 12v to turn on the relay).

You can try to check the relay, but I don't think that this could be the problem... what the LP-2020B has is a DPST relay File:Relay symbols.svg - Wikipedia, the free encyclopedia the solenoid two pins are the ones mentioned before, and the 4 pins on the other side connect negative from chip with negative to speaker. What could cause a relay to stop working is, a broken solenoid (will have 0 ohm resistance if its shorted, or infinite if its broken) or broken switch contacts (but in this case you should hear de "click").

Thank you very much..

What I've noticed here is that those 2 pins are connected through a diode & its working fine.. (I mean the diode)But I'm unable to receive the "click" sound.. So my idea is that the relay is not functioning well due to some unknown reason .. I'll try to bypass this part .. (manually connect speaker negative wire to chip negative out)..I'll try it ..

Thanks
 
Thank you very much..

What I've noticed here is that those 2 pins are connected through a diode & its working fine.. (I mean the diode)But I'm unable to receive the "click" sound.. So my idea is that the relay is not functioning well due to some unknown reason .. I'll try to bypass this part .. (manually connect speaker negative wire to chip negative out)..I'll try it ..

Thanks

Well, the diode is to avoid that the current hold by the solenoid come back and could damage other components (it's a typical circuit, some transistors -the black components with 3 pins- control the relay http://img299.imageshack.us/img299/8766/relaydrivergg8.jpg ). Be careful to not bypass any components in the output stage, and do not make ground contact, as it can damage the chip.
 
like here Fastron SMD Hochstrom Induktivität Serie PISR 1.3 A im Conrad Online Shop

It is easy to mount these, you only have to scratch away a little bit of the silkscreen (green stuff). Then solder it there, to remove it is a little bit trickier ;-)

I've seen these on ebay http://cgi.ebay.es/ws/eBayISAPI.dll?ViewItem&item=250958137468 which looks nice, have 10uh 4.8A and shielded (but they are 6.5mm height, probably will not fit under the PCB on the original case). If I finally recover my Lepai with the new chip will try them.
 
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they have a current up to 1,4 A - should be enough.

Well, the recommended values by Tripath are 3A for the TA2020, I won't go behind that... inductance falls when current goes over maximum value, so they will become useless.

And they quality is also important, a bad coil could cause the over-current protection feature to malfunction and damage the chip... on the TA2022 (which is a more powerful chip with similar technology) there is a long description about the output filter and its importance "The core material and geometry of the output filter inductor affects the TA2022 distortion levels, efficiency, over-current protection, power dissipation and EMI output." you can have a look at the output filter design section http://g.dubuc.free.fr/pdf/TA2022.pdf

I don't know how much current capable are the ones present on stock Lepai... but pointing in make an improvement, I would try to get at least 3A 10uH (toroids ideally, but are too expensive, so shielded probably will do the job and they are not so expensive).

These are 3A 10uh shielded with 4,5mm height so will be also ok http://www.ebay.es/itm/Lot-5-SLF101...10uH-Tol-20-4040-Case-TDK-A3232-/250911958419
 
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