Hello to everyone,
i have been reading another thread in this forum with a similar issue:
http://www.diyaudio.com/forums/car-audio/188895-weconic-amp-protection.html
the only difference with Mote's issue is that i have no offset voltage in the outputs.
With the same jumper disconnected the amp works perfectly. I have done everything just like Perry suggested in the comments and i am kind of lost now.
All the small signal and power transistors of the board are ok (i removed and tested one by one) so there is no other option than a resistor or a capacitor (out of value).
On the other hand, i have been using this amp for a while now and the weird thing is that in the past, sometimes (while using it) it got protected, so i had to power it off, wait a couple of minutes and then power it on again to make it work. After a couple of months it got always in protection mode. This is why i guess it may be an R or C.
With the jumper J110 disconnected (see image), i measure the voltage on the amp side and the voltage is about 0,08V and i have audio output, while working i reconnect the jumper and it keeps working without protecting, but when i turn it off and on again it protects.
Any of you have the schematic of this amp?
Thank you very much in advance for your help.
Valentin
i have been reading another thread in this forum with a similar issue:
http://www.diyaudio.com/forums/car-audio/188895-weconic-amp-protection.html
the only difference with Mote's issue is that i have no offset voltage in the outputs.
With the same jumper disconnected the amp works perfectly. I have done everything just like Perry suggested in the comments and i am kind of lost now.
All the small signal and power transistors of the board are ok (i removed and tested one by one) so there is no other option than a resistor or a capacitor (out of value).
On the other hand, i have been using this amp for a while now and the weird thing is that in the past, sometimes (while using it) it got protected, so i had to power it off, wait a couple of minutes and then power it on again to make it work. After a couple of months it got always in protection mode. This is why i guess it may be an R or C.
With the jumper J110 disconnected (see image), i measure the voltage on the amp side and the voltage is about 0,08V and i have audio output, while working i reconnect the jumper and it keeps working without protecting, but when i turn it off and on again it protects.
Any of you have the schematic of this amp?
Thank you very much in advance for your help.
Valentin
Last edited:
With J110 in place, which of the 4 protection circuit transistors in the audio stage, when removed (all 3 others in the circuit) allows the amp to operate normally?
First of all I have connected only 2 speakers in bridge mode, which means i am loading only between red (-) and yellow (+) cables (see the picture).
Then, following the disconnected jumper (red trace in the picture) it is connected to four 22K resistors (R163-> red cable = R-; R263-> yellow cable = R+; R363-> red cable = F-; R463-> yellow cable = F+). I guess those are just like pullup and pulldown resistors to detect the dc offset between the bridged outputs, if one of them is unbalanced this trace (J110) will trigger the protection. There is nothing else than those 4 22K resistors connected to this trace.
Something i can't understand is that, with the jumper disconnected on the protection circuit side, the voltage is always 0V, which makes sense; but on the amp side during the start-up i have a peak of 3.5V during a second and then it goes to 0V. I bet this peak voltage is triggering the protection, since after the start-up if i reconnect the jumper everything is working fine.
Regarding to the 4 protection transistors, i am not sure which are they.
I attach you the other pictures for reference.
Please, notice that in this picture there are no red and yellow cables for the R- and R+, F-, F+ (only green and yellow). I am using the first picture (zoomed) to explain.
Then, following the disconnected jumper (red trace in the picture) it is connected to four 22K resistors (R163-> red cable = R-; R263-> yellow cable = R+; R363-> red cable = F-; R463-> yellow cable = F+). I guess those are just like pullup and pulldown resistors to detect the dc offset between the bridged outputs, if one of them is unbalanced this trace (J110) will trigger the protection. There is nothing else than those 4 22K resistors connected to this trace.
Something i can't understand is that, with the jumper disconnected on the protection circuit side, the voltage is always 0V, which makes sense; but on the amp side during the start-up i have a peak of 3.5V during a second and then it goes to 0V. I bet this peak voltage is triggering the protection, since after the start-up if i reconnect the jumper everything is working fine.
Regarding to the 4 protection transistors, i am not sure which are they.
I attach you the other pictures for reference.
An externally hosted image should be here but it was not working when we last tested it.
Please, notice that in this picture there are no red and yellow cables for the R- and R+, F-, F+ (only green and yellow). I am using the first picture (zoomed) to explain.
Last edited:
You can remove the resistors that connect to that trace, one at a time, instead of removing the transistors.
Dear Perry,
here is the update. I have discovered that the problematic channel is the REAR one. I had to disconnect R163 and R263 because, as the line must be balanced, if i only disconnect one of them the protection is triggered.
It is something related to the unbalanced output (dc levels), but i can't figure out where because it is only during the start-up phase.
I have re-checked all the transistors of the Rear stage and all of them are good.
What do you recommend me to do now?
It is kind of hard for me to "picture" the schematic in my head because i have never seen one of this kind with all the protection transistors. Do you have any similar as a guide?
Thank you very much once again.
here is the update. I have discovered that the problematic channel is the REAR one. I had to disconnect R163 and R263 because, as the line must be balanced, if i only disconnect one of them the protection is triggered.
It is something related to the unbalanced output (dc levels), but i can't figure out where because it is only during the start-up phase.
I have re-checked all the transistors of the Rear stage and all of them are good.
What do you recommend me to do now?
It is kind of hard for me to "picture" the schematic in my head because i have never seen one of this kind with all the protection transistors. Do you have any similar as a guide?
Thank you very much once again.
Great idea Perry!,
i have isolated a small part of the circuit where the problem should be.
It is in FRONT+ section (sorry it wasn't rear, my mistake before).
Now i have checked D102, D202, D201, C224, C226, C225, C421 and all are ok.
All the output transistors seem to be the original ones and in case they are not matched the circuit should compensate the difference right?
Do you have any other idea to check?
Thanks.
i have isolated a small part of the circuit where the problem should be.
It is in FRONT+ section (sorry it wasn't rear, my mistake before).
Now i have checked D102, D202, D201, C224, C226, C225, C421 and all are ok.
All the output transistors seem to be the original ones and in case they are not matched the circuit should compensate the difference right?
Do you have any other idea to check?
Thanks.
An externally hosted image should be here but it was not working when we last tested it.
Is this still happening?
on the amp side during the start-up i have a peak of 3.5V during a second and then it goes to 0V.
on the amp side during the start-up i have a peak of 3.5V during a second and then it goes to 0V.
Over the protection line (without the speakers) and with the resistor R263 disconnected only i have no DC but, in the F+ i have more than 20V (respect to gnd) during the start-up and in F- i have 0V always.
Check the output of the various op-amps in the preamp section to see if any have excessive DC voltage on them. A high DC voltage could surge through the coupling capacitors on startup.
All the outputs are at exactly half of the rail (14V).
i also checked all the small signal transistor polarization diodes diodes and all of them are fine.
i really don't have any clue about what else can be...
should i have to start changing all capacitors one by one?
i also checked all the small signal transistor polarization diodes diodes and all of them are fine.
i really don't have any clue about what else can be...
should i have to start changing all capacitors one by one?
Place the black probe on one of the non-bridging speaker terminals and measure the op-amp voltage again. Make sure to note the polarity (positive/negative).
What is the DC voltage measured directly across the B+ and ground terminals?
What is the DC voltage measured directly across the B+ and ground terminals?
13,9V in all the op-amp VCC (pin8) and -13,9V in all the VEE (pin4). Also in all the outputs and inputs 0V.
- Status
- Not open for further replies.