Lepai T-Amp with TA2020

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col

col

Member
Joined 2008
minirig.org.au
12v lead battery? batteries just charged can have voltage up around 14v. Do you have a multimeter? you should measure the voltage. I don't recommend connecting anything over 13.5v.

The constant ticking is the amp trying to reset itself. If you leave it like that it will burn out the chip. If you remove the zener, the little glass orange and black diode near the chip. It will stop the amp resetting. Then you need to work out which inductor is shorted. Follow Mike's directions:

"Try removing the zener diode between pin 18 (fault pin) and pin 11 (I think), and see if you still get ticking.

With the zener gone, try connecting an LED and 2k resistor between pin 18 (fault pin) and GND and see if the LED lights up."

col.
 
MikeHunt79

MikeHunt79

Member
Joined 2003
col said:
I might take out the zener too! Mike, did you replace it with a wire link or just remove it?

col.
Click to expand...
I removed it and left it open circuit, it's not needed at all and I'm not sure why they put it in! Take a look at the TA2020 datasheet for the nitty gritty, basically the ticking sound is the amp trying to start up despite there being a problem, and the ticking can lead to a broken TA2020.
whelibob said:
thanks, for the help. so you think the tripath chip is now broken? i used 12V lead battery. adding a new output inductor with higher capacitance wont repair it anymore?
Click to expand...
I could be the TA2020, it could be a short on the outputs where the inductors and diodes are, I'd remove the zener and wire up the fault LED if you've modded it already, otherwise I'd send it back. :)
 
MikeHunt79

MikeHunt79

Member
Joined 2003
col said:
Mike, which side of the zener is pin 17 and which is 18? I think I might wire a fault led in and glue it to the front.

col.
Click to expand...

The zener goes from pin 11 to pin 18, if you can post a close up of the chip I can highlight it in photoshop for you. :)

i'll try and get a photo of mine with no zener, but I've only got a camera-phone so it may not work too well...
 
MikeHunt79

MikeHunt79

Member
Joined 2003
panda360

panda360

Member
Joined 2009
Calamaro said:
panda, just bypass the electrolitic with the 100nF film cap: solder its legs on electrolitic legs. The film cap (100nF) is non polarized so you don't have to pay attention to + and - legs.
If you prefer you can solder the little film cap under the board
Click to expand...


Hi Cal,

I just finished the modification by passing the opamp. Except input cap. (I can't good quality 470uf cap at this moment. ) The sound quality is better than before. But the sound level is lower. Before mod, I turn to 12 oclock position is enough. After mod, I need to turn to 1 o'clock position.

Anyway, I am happy with this amp.

Thank you.
:D
 
MikeHunt79

MikeHunt79

Member
Joined 2003
col said:
just removed the zener and put a 2k resistor with led on the No18 pin. drilled a hole in the front between the tone controls to mount. So I now have a fault led :D

col.
Click to expand...
Nice work. :)

Some people at the 41Hz forum suggest shorting the speaker outs is a good way to test if the fault LED works, but I'm not sure if I'm that brave to do it to my Lepai! :bigeyes:

I'm making a perpex faceplate for mine, I've found that the pot I want to use is a little large so I've had to improvise... :smash:
 
MikeHunt79

MikeHunt79

Member
Joined 2003
Hey guys, another Lepai arrived today, and it appears to be a little different, I guess this could be Mark 3?

Here's a pic, new (mk3) on the right and my old (modded mk2) on the left:
An externally hosted image should be here but it was not working when we last tested it.


As you can see the mk3 has notches for mounting bolts, and I've also found that the switch now turns the LED on and off, but there is a big turn on thump... I guess the switch must switch the power and mute is now disabled?

I haven't opened it up yet, but when I do I'll post some more pics. :)
 
MikeHunt79

MikeHunt79

Member
Joined 2003
I think I've finished tinkering with mine for today:
An externally hosted image should be here but it was not working when we last tested it.


The red LED on the bottom left is the fault LED, the orange wire has a 2k2R resistor from pin18 for the fault LED. The big cap on the left is exactly like Calamaro's power mod. :) I've also wired 4 x white LED in series so when I'm powering this amp from my Li-ion battery pack I can see when the voltage goes below 9v when the LED's go dim.

I've replaced the volume pot with a 50k A&B pot which is a little large so I've had to have it floating and have the front panel hold it in place.

I've made a new front panel from 4mm perpex, and because the front panel is now removable, I can now mount decent quality RCA connectors on the rear panel. I've gone for a 4pin molex connector for the speaker connectors so I can quickly disconnect and reconnect this in the car...

View from front:
An externally hosted image should be here but it was not working when we last tested it.


I need to buy a knob for the volume pot, right now I'm just using 6mm washers taped together! :D I'm used a drilled 2p coin as a washer for the volume pot. :clown:

Once the new op-amps arrive I think I'll try swapping out the JRC4558, and I have still yet to try tone control bypass and I still need to wire in a mute switch.... Right now it's just shorted so it's unmuted the whole time.
Calamaro said:
I have that one (the new). I think it has the same pcb.
Click to expand...

Yep, I just taken it apart and it is the same PCB... Pic:
An externally hosted image should be here but it was not working when we last tested it.


I guess this could be a the early version after all? Did that one have the LED switch on and off with the switch on the front?
 
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