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Old 23rd June 2011, 05:57 AM   #811
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Default Missing resistors?

Hello gentlemen. New to these forums and the DIY audio experience as well. I just bought a Lepai LP-2020A+ amp, blue pcb with tone bypass and two op-amps, and R41 and R40 are missing on the board. Since I can't find a pic that has already been posted that shows that section of the board in detail, does anyone else have resistors R41 and R40 on their board?

The quality control on these seems pretty horrible but you still can't beat them for the price.
My power cap came crushed along with bent heat sink fins. Somehow the amp still works pretty well.

My relay appears to be different than the ones posted. The relay on my board is a blue OSA-SS-212DM3. It doesn't seem to help the turn on/off pop that much, as the speakers will give a slight pop when the relay clicks on or off. I imagine this might have something to do with other components, the relay itself, or perhaps both?

One more question to the community, is there any good reason why this newer version would have substantially more caps and resistors? All the surface mounted components seem a bit excessive considering the simplicity of much more expensive, higher rated amps that use the same Tripath TA2020 chip.
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Old 27th June 2011, 03:34 AM   #812
lithoc is offline lithoc  Malaysia
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Hi,

Anybody have schematic for TA2020A+(one with blue pcb & tone defeat button) preamp section.

I'm studying the tone control of this unit. It's easier for me if anyone already have the schematic.



Thank you in advance
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Old 28th June 2011, 08:30 PM   #813
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I just received my Lepai LP-2020A+ from PE. Couldn't resist the price, and I can use it for a casual-listening bookshelf system in a worst-case situation (excluding giving/throwing it away). I'm only a few songs into it, but it doesn't sound half bad using the included ps. The tone control seems a little screwy; I think someone mentioned the better bass response with the tone enabled, and I'm finding that true also. I have a 5A linear supply I plan to use permanently. Gonna do some more listening and "electron exercising" before opening it up.
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Old 29th June 2011, 01:38 AM   #814
lithoc is offline lithoc  Malaysia
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I think the tone defeat feature is useless. There are no low end bass and high.
Right now, I maxed out my bass but still not enough. Still looking for ways to boost the bass but wanted to modify the cap so that by boosting the low end bass, it won't affect the mid too much. Now the mid already sound muddy.
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Old 30th June 2011, 07:57 PM   #815
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Quote:
Originally Posted by toxaris View Post
Hello.
I have searched this thread but I cant find an answer to my question.

I have bought a Lepai TA-2020A+ amp and its driven by a 12V 55Ah carbattery.
If I want to add a fuse between tha battery and the amp, what is recommended?
From what I know a 6A fuse is just 1A above specifications.
Will that work or should I go higher or lower?

Thanks.
Daniel Persson.
I'm using a 12V car battery too - I connected it to the amp via a 2A fuse and it hasn't blown yet (8 ohm speakers). The current is under an Amp for normal listening levels... I would say 6A is probably excessive. These amps are about 85% efficiency, so at 40W (4 ohms) output I wouldn't expect it to draw more than 4A at 12V. The low power consumprion is one of things that first attracted me to the TA2020... I'm running mine off a 12V solar system charging a car battery, so efficiency was important to me!
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Old 2nd July 2011, 03:48 PM   #816
Sigrm is offline Sigrm  Norway
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Quote:
Originally Posted by padgettr View Post
From the data sheet for the TA2020:

Min: 8.5V, Max: 14.6V (I havent tested these exactly though)

However, I wouldn't recommend exceeding 13.5V with the Lepai circuit.
What happens if the voltage drops below 8,5V? Is it possible to change this to something like 11,5V to protect a SLA battery?

Another question:
Can the amp get damaged if I run it with only one output channel driving my speakers?

Thanks in advance!
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Old 4th July 2011, 12:45 AM   #817
pkozul is offline pkozul  Australia
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Default My Lepai is dead?

Hi there,

I think my Lepai is fried. Not sure whether I should try and replace the TA2020 chip or buy a new Lepai and start over.

A few months ago, I modded the amp in several ways Ė removed the zener , replaced the input caps, bypassed the tone controls, replaced the inductors with toroids, etc. After months of nice listening, it suddenly stopped working.

When I switch on the amp, I still get the usual minor thump noise, but no sound is being output (except for some slight hissing). I tried different speakers to make sure, but same result. I checked the PCB, solder joints, and visually inspected the components, and everything looks fine.

Thanks to some tips from Dr. Lex, I perfromed the following checks...

- Checked the power supply. It produces 12.9V with and without the Lepai connected.
- Measured the voltage between ground and pin 18 of the amplifier chip, and it did produce a 5V reading (fault).
- Touched pin 10 (and later pin 13 separately) with a wire in my hand while the Lepai was switched on but no sound was produced on my speakers.

Iím just a beginner at electronics, so Iím learning as I go along.

Using the multimeter, I also checked for continuity to make sure that the path between the input signal and the TA2020 chip. I also check the input caps and resistors, and they all appear fine too.

So, if thatís the end of this chip, is it easy enough to replace just the TA2020 chip and leave everything else as is (assuming I can get hold of a chip)? Iíd prefer that option as I think it will be quite a hassle to remove all the components I upgraded, and then move them to a new Lepai.

Thanks!
Pete
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Old 4th July 2011, 01:54 PM   #818
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try this link.....

2PCS, Tripath Class D Amplifier TA2020 IC NEW | eBay
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Old 7th July 2011, 03:45 AM   #819
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I bought a Lepai Tripath 2020 on Amazon for under $30 with shipping, cut the wal wart wire to attach to a car cigarette lighter adapter, went over it 4 times, making sure I had the center connector to the hot side, plugged it in, and fried it, since I actually had the center wire connected to the ground! Doh! Double Doh!!

I haven't soldered on an electronics project for almost 40 years, but will try anything. Can somebody direct me towards any possible fix? I am thinking maybe there's a polarity protection diode I can replace? Sorry for not studying all the pages myself.

Thanks!
Steve
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Old 7th July 2011, 05:33 AM   #820
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It isn't gonna be as easy as polarity protection diode replacement. I would put a signal injector at the input of each IC to determine if anything gets thru to the speakers. If it doesn't, I'd just get a new amp. Judging from the link above, a new Tripath chip is going to cost roughly half of what the complete Lepai costs. If it's just a blown opamp, I'd replace it.
The signal injector could be practically anything. A small radio or soundcard output for example. Use the proper jack and insert a small ~1uF capacitor in series - one lead connects to the cable and the other lead is the probe.
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