I applied 14V to the amp and i used a 100Hz sinus and the gain all up with a 4 Ohm resistor on Speaker output.
I adjusted the input signal to one point where the amp pulls 5A.
I put 6 fingers to the output fets on the working channel.
No finger hurts after 1 minute!
I apllied the same signal level to the " defective " channel and after 20 seconds i have to take my finger away from Q126.
This channel pulls 0.5A more from the supply than the other one with identical signal and has a slightly higher output, maybe 1Vrms on Speaker output.
In Bridge mode also some FETs of the working channel get hot.
The complete heatsink was very warm like pushing the amp to the limit in bridge mode with the same 4 ohm resistor load.
EDIT:
amp sounds good, but when i connect the amp to my 65a psu some FETs burn and mmbta06,56, diodes near the driver transistors.
the working channel puts out max power and nothing burns.
BR
Andi
I adjusted the input signal to one point where the amp pulls 5A.
I put 6 fingers to the output fets on the working channel.
No finger hurts after 1 minute!
I apllied the same signal level to the " defective " channel and after 20 seconds i have to take my finger away from Q126.
This channel pulls 0.5A more from the supply than the other one with identical signal and has a slightly higher output, maybe 1Vrms on Speaker output.
In Bridge mode also some FETs of the working channel get hot.
The complete heatsink was very warm like pushing the amp to the limit in bridge mode with the same 4 ohm resistor load.
EDIT:
amp sounds good, but when i connect the amp to my 65a psu some FETs burn and mmbta06,56, diodes near the driver transistors.
the working channel puts out max power and nothing burns.
BR
Andi
Last edited:
Set your multimeter to hi-resolution mode.
Measure the resistance between all 3 gates for each of the 4 banks of output FETs. Do all read the same?
Do the same for all 3 FETs in each of the 4 banks, but this time, between the emitter legs. Do they read the same?
Measure the resistance between all 3 gates for each of the 4 banks of output FETs. Do all read the same?
Do the same for all 3 FETs in each of the 4 banks, but this time, between the emitter legs. Do they read the same?
Here is what i got, with probe to probe 0,04 ohm.
Working channel:
gate:
Q224-Q219: 19,88 ohm
Q224-Q226: 19,99 ohm
Q219-Q226: 19,99 ohm
source:
Q224-Q219: 0,26 ohm
Q224-Q226: 0,26 ohm
Q219-Q226: 0,26 ohm
gate:
Q225-Q215: 20,04 ohm
Q225-Q227: 19,92 ohm
Q215-Q227: 19,96 ohm
source:
Q225-Q215: 0,26 ohm
Q225-Q227: 0,26 ohm
Q215-Q227: 0,26 ohm
" defective " channel:
gate:
Q127-Q115: 19,98 ohm
Q127-Q125: 19,94 ohm
Q115-Q125: 19,92 ohm
source:
Q127-Q115: 0,29 ohm
Q127-Q125: 0,29 ohm
Q115-Q125: 0,28 ohm
gate:
Q126-Q119: 19,99 ohm
Q126-Q124: 20,04 ohm
Q119-Q124: 19,90 ohm
source:
Q126-Q119: 0,27 ohm
Q126-Q124: 0,26 ohm
Q119-Q124: 0,27 ohm
Again, thank you very much for helping me with that issue.
Working channel:
gate:
Q224-Q219: 19,88 ohm
Q224-Q226: 19,99 ohm
Q219-Q226: 19,99 ohm
source:
Q224-Q219: 0,26 ohm
Q224-Q226: 0,26 ohm
Q219-Q226: 0,26 ohm
gate:
Q225-Q215: 20,04 ohm
Q225-Q227: 19,92 ohm
Q215-Q227: 19,96 ohm
source:
Q225-Q215: 0,26 ohm
Q225-Q227: 0,26 ohm
Q215-Q227: 0,26 ohm
" defective " channel:
gate:
Q127-Q115: 19,98 ohm
Q127-Q125: 19,94 ohm
Q115-Q125: 19,92 ohm
source:
Q127-Q115: 0,29 ohm
Q127-Q125: 0,29 ohm
Q115-Q125: 0,28 ohm
gate:
Q126-Q119: 19,99 ohm
Q126-Q124: 20,04 ohm
Q119-Q124: 19,90 ohm
source:
Q126-Q119: 0,27 ohm
Q126-Q124: 0,26 ohm
Q119-Q124: 0,27 ohm
Again, thank you very much for helping me with that issue.
I still have parts from the same batch and i didnt try it.
It seems i should give it a try. 🙂
Maybe i heated the mehsa board too much and damaged the FET....
Time to go to bed, i will let you know then.
Have a nice day and again thanks a lot !!
BR
Andi
It seems i should give it a try. 🙂
Maybe i heated the mehsa board too much and damaged the FET....
Time to go to bed, i will let you know then.
Have a nice day and again thanks a lot !!
BR
Andi
Hi Perry ! 🙂
Finally the amp works perfect, the issue wasnt the amp.
Its weird, but i think it was my small 70$ 0-30V / 10A powersupply.
Ich changed the FET again and the problem was still there. Amp heated up quick when i pull around 5 amps out of the supply.
I got a little frustrated and i decided to hook the amp to my 50A power supply and try to drive it hard mono bridged 4 ohms with 100Hz sinus-signal.
Even when i pull 20 amps the amp didnt get as hot as in the test with the other powersupply. So i decided to kick it harder 😀
My PSU does 13.7V and i noticed that i can even pull around 80amp ( 13.6V ) out of it without issues.
The amp puts out around 700 watts ( everything tested quick and dirty ). During delivering that amount of power the amp got a little hot, but that felt normally to me.
Efficiency was around 60-65%.
The 4 ohm load got warm and Resistance grew up to 4.3 ohms then.
I never heard of problems with PSUs...what can be the issue?
The last component i changed was D5 , can you tell me what it does in the circuit because the amp worked even with D5 open...
And again thank you very much for your support!!
Best regards!!!
Andi
Finally the amp works perfect, the issue wasnt the amp.
Its weird, but i think it was my small 70$ 0-30V / 10A powersupply.
Ich changed the FET again and the problem was still there. Amp heated up quick when i pull around 5 amps out of the supply.
I got a little frustrated and i decided to hook the amp to my 50A power supply and try to drive it hard mono bridged 4 ohms with 100Hz sinus-signal.
Even when i pull 20 amps the amp didnt get as hot as in the test with the other powersupply. So i decided to kick it harder 😀
My PSU does 13.7V and i noticed that i can even pull around 80amp ( 13.6V ) out of it without issues.
The amp puts out around 700 watts ( everything tested quick and dirty ). During delivering that amount of power the amp got a little hot, but that felt normally to me.
Efficiency was around 60-65%.
The 4 ohm load got warm and Resistance grew up to 4.3 ohms then.
I never heard of problems with PSUs...what can be the issue?
The last component i changed was D5 , can you tell me what it does in the circuit because the amp worked even with D5 open...
And again thank you very much for your support!!
Best regards!!!
Andi
I don't know how the 12v power supply could have made one out of 3 output transistors overheat.
D5 delivers positive regulated voltage to the power supply driver components to boost the drive voltage and also prevent the drive voltage from going too low when the battery voltage drops. The amp worked because the supply voltage for those components was still being provided by the remote voltage.
D5 delivers positive regulated voltage to the power supply driver components to boost the drive voltage and also prevent the drive voltage from going too low when the battery voltage drops. The amp worked because the supply voltage for those components was still being provided by the remote voltage.
Thanks Perry!!
I was confused that the amp pulls around 60 watts and puts out way less than 50%.
I thought that those amps have an efficiency of around 60-70% regarding the birth sheets i saw.
Is it possible that these amps have a bad efficiency at lower output levels and get more efficient the higher the output power gets?
BR
Andi
I was confused that the amp pulls around 60 watts and puts out way less than 50%.
I thought that those amps have an efficiency of around 60-70% regarding the birth sheets i saw.
Is it possible that these amps have a bad efficiency at lower output levels and get more efficient the higher the output power gets?
BR
Andi