do i need to match q1/q2 and q9/q10? right?
what parameter do i need to mach? sorry to ask but it is the first time i m doing this matching operation and i want to do it right.
i bought 50 from each type.
what parameter do i need to mach? sorry to ask but it is the first time i m doing this matching operation and i want to do it right.
i bought 50 from each type.
Hello,
please HELP 😕
When setting VAS biasing, I was carelessly manipulating the multimeter probe and a short time I connected the legs R25 and R39.
It sparkled a bit and the R4 resistor burned out before I turned off the power on. Shown in the picture below.
What was destroyed? Transistor? Who?
I'm not an expert to find a mistake. I can only measure components if I know which ones.
I hope this is a small problem and I can repair it.
Thank you for the advice.
please HELP 😕
When setting VAS biasing, I was carelessly manipulating the multimeter probe and a short time I connected the legs R25 and R39.
It sparkled a bit and the R4 resistor burned out before I turned off the power on. Shown in the picture below.
What was destroyed? Transistor? Who?
I'm not an expert to find a mistake. I can only measure components if I know which ones.
I hope this is a small problem and I can repair it.
Thank you for the advice.
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Por favor, note que este é um fórum em inglês
Hello,
please HELP 😕
When setting VAS biasing, I was carelessly manipulating the multimeter probe and a short time I connected the legs R25 and R39.
It sparkled a bit and the R4 resistor burned out before I turned off the power on. Shown in the picture below.
What was destroyed? Transistor? Who?
I'm not an expert to find a mistake. I can only measure components if I know which ones.
I hope this is a small problem and I can repair it.
Thank you for the advice.
Hi Robodo.
Check all the resistors. Replace the burnt ones.
Check all bipolars for base-emitter and base-collector voltage with multimeter in diode test mode. For Q1,3,5,7,9 black probe goes to base, for Q2,4,6,8,10 black probe goes to base. Pin 2 is base for small bipolars and pin 1 is base for Q9/Q10. If any junction shows open or short, replace that transistor. Remove jumpers before probing.
Hello Shaan,
I was able to match q1 and q2 perfect but on q9/q10 i m having trouble.
On a batch 30 mje340 and 30 350 i have no 340 higher than 80 hfe and 350 no lower than 119hfe.
Should i buy more? what is the max diference alowed?
Sorry for this question but i m learning.
Thks.
Hi Pistollero.
A difference of upto 25% is fine. See if you can get 340 with 100 or more hFE.
No need to say sorry for asking questions.
Bests.
A difference of upto 25% is fine. See if you can get 340 with 100 or more hFE.
No need to say sorry for asking questions.
Bests.
Thks... for the help. I will need to buy more to get the right ones....Hi Pistollero.
A difference of upto 25% is fine. See if you can get 340 with 100 or more hFE.
No need to say sorry for asking questions.
Bests.
[emoji106][emoji846]
Hi shaan,
Thank you for your help. I measured all the resistors and replaced only the burned R4, the others were fine. Then I measured the transistors and I detected faulty Q2
First I also desoldered the Q4, Q8 and Q10 because I thought they were also defective,...
...before I found out that for NPN transistors it is necessary to apply a red probe goes to base and then these transistors were already good.shaan said:
So I soldered them back. I'm glad I have more of these transistors, because I destroyed the desoldered ones.
After attaching the finished board to the heatsink and connecting the power supply. Everything seems to be fine.
Tomorrow I will make setup VAS, Offset and more, I'm finishing today.
I don't like two differences. It just seems to me that the LED D6 versus D5 is a little dimmer. And resistance between the output terminal and heatsink body is 4,7 MOhm.
This does not happen with the second PCB module. I already have it installed and all setup fine.
Any advice? Thank you.
Robert
Replace the led that's dim.
If it's showing 4.7Mohm without heatsink connected to psu ground then somewhere there is a slight leakage between mosfet backs and heatsinks. Replace the insulators.
Hi shaan,
the resistance between ground and output is ok. I measured it with the power supply connected
Today I tried to set the VAS, but the mV value didn't want to change, still 0mV, even though I was rotating VR1 and VR2. As the VR2 rotates, LED D6 dims to completely dark. If I turned the trimmer back to the maximum resistance, then is the light back on D6 😕
I'm finishing today, I won't continue until after the weekend. I should give time to my family 😱🙂
Robert
the resistance between ground and output is ok. I measured it with the power supply connected
Today I tried to set the VAS, but the mV value didn't want to change, still 0mV, even though I was rotating VR1 and VR2. As the VR2 rotates, LED D6 dims to completely dark. If I turned the trimmer back to the maximum resistance, then is the light back on D6 😕
I'm finishing today, I won't continue until after the weekend. I should give time to my family 😱🙂
Robert
I salvaged another amp (i guess peeceebee has priority [emoji1]) to get mje340 that mach well with the mje350 I had already.. problem solved and one board almost done.. 
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