In my Poppulse T180 amp one of the TA 2022 IC-s (one per channel, BTL mode) gave up the fight (no heat conducting paste between the the IC, and the heatsink ! ) , so I ordered one and replaced tha failed chip. The problem is, that now I have almost 1V DC on the speaker terminals, and the circuit uses two trimpots to adjust the 0V DC on the output. I have the data sheet of the IC, but it does not tell you how to adjust the DC offset in BTL mode. Any idea?
Attachments
1 volt is a lot!
It's been awhile, but what I remember is that DC on the input means DC on the output. Of course there is always DC on the input, so that has to be tweaked a little to null the output. The trim pot circuit allows you to that. Each channel should have its own trimmer, so that they can be set individually.
It's been awhile, but what I remember is that DC on the input means DC on the output. Of course there is always DC on the input, so that has to be tweaked a little to null the output. The trim pot circuit allows you to that. Each channel should have its own trimmer, so that they can be set individually.
Last edited:
En dual mono (pont), le réglage de l'offset peut être plus compliqué, sachant qu'il y a deux réglages par canal...
Mesurez la sortie incriminée avec les entrées court-circuitées avec un voltmètre.
Mesurez la sortie incriminée avec les entrées court-circuitées avec un voltmètre.
En Anglais, SVP This is an English langauge forum - which should be obvious.
And yes, be sure to measure with a load attached. 4-16 ohms will do fine.
And yes, be sure to measure with a load attached. 4-16 ohms will do fine.
Of course I know all of the above, but the problem is: I can adjust the output 0 Volt DC with either trimpot (one R up, one R down, and the oppsite way too, but there must be a way to find out which one is the proper setting. In normal stereo -non BTL- mode (I worked with this chip few times before) the trimpots are usually set NOT in their middle position to achieve zero DC at the speaker terminal.... 🤔 And of course, I measure the offset with a dummy load.
Also, -as I said in the initial post- there are TWO trimpots for each channel.
Also, -as I said in the initial post- there are TWO trimpots for each channel.
Hi Syra
I've got a Poppulse 150 that shows the left channel very attenuated.
I've found your thread and noticed that in my amp (single Ta2022) there is a single pair of trimpot (VR1 & VR2) similar similar to yours
https://photos.app.goo.gl/fKjV3svcXNNA9ajBA
Maybe they can be used to give the missing gain to the left channel ?
How to identify the left channel between vR1 & VR2 ?
Can be directly set, with with source & speakers connected, and turning the two screws listening to the speakers ?
Given your experience, any suggestion how to operate the settings ?
Thanks for your help,
BR
Giuliano
I've got a Poppulse 150 that shows the left channel very attenuated.
I've found your thread and noticed that in my amp (single Ta2022) there is a single pair of trimpot (VR1 & VR2) similar similar to yours
https://photos.app.goo.gl/fKjV3svcXNNA9ajBA
Maybe they can be used to give the missing gain to the left channel ?
How to identify the left channel between vR1 & VR2 ?
Can be directly set, with with source & speakers connected, and turning the two screws listening to the speakers ?
Given your experience, any suggestion how to operate the settings ?
Thanks for your help,
BR
Giuliano
In the case of the 150 it is easy. With a 8 ohm 10W dummy load connected to each speaker terminal and no input signal, measure the DC voltage across the resistor. You can find out really quick which trimpot belongs to which channel.... If you rotate the adjustment screw gently, you will see whether the voltage changes on the given channel or not. If not, it is the other trimmer.... Then -after about 30 minutes of warmup time- adjust the corresponding trimpot to minimum reading on the 200 mV DC range setting on your multimeter. 5-20 mV is OK, don't worry too much about playing it down to zero. After another half an hour repeat the measurement, and readjust it if necessary.
Depending on ambient temperature and output power it will change sligthly anyway, but as I said don't bother with a few mV-s up or down.
In the case of the T180 -because it is operating in BTL mode- it is more difficult, but it can be done with adjusting the trimpots while measuring the voltages on each speaker terminal relative to the main (common) ground point on the power supply of the amplifier. One trimpot is adjusting the output zero on on the + terminal, and the other on the - terminal.
The reason for this being that the outputs in this mode are not ground related, but floating. (be aware that none of the terminals can be connected to ANY common ground point in the system!)
BTW: adjusting the trimpots do nothing with the gain of the channels, they are only for output DC balance setting.
Depending on ambient temperature and output power it will change sligthly anyway, but as I said don't bother with a few mV-s up or down.
In the case of the T180 -because it is operating in BTL mode- it is more difficult, but it can be done with adjusting the trimpots while measuring the voltages on each speaker terminal relative to the main (common) ground point on the power supply of the amplifier. One trimpot is adjusting the output zero on on the + terminal, and the other on the - terminal.
The reason for this being that the outputs in this mode are not ground related, but floating. (be aware that none of the terminals can be connected to ANY common ground point in the system!)
BTW: adjusting the trimpots do nothing with the gain of the channels, they are only for output DC balance setting.
Last edited:
