Hello i have two channel sourcemeter 2602 with one bad channel.
Bad channel get full amplitude on output. That's cause one channel power supply to overload.
On the bad channel:
One of LM337 near the capacitors gets hot, and one LM317 have the room temperature, on working channel they both gets quite hot
I thinks, that it's because one part of pre-amp eat more current.
I try to trace and found one bad smd transistor Q32, marked as 2.(dot)A LLI 2.A LLI
Looks like 2n3906 or maybe some different type?
It's connected with diode(zenner?) VR7
When i de-solder bad transistor and check it with transistor tester. That shows that its BJT-PNP with hFe=0 Ic=0 Ube=0 (BAD).
Then i check resistance to GND from solder pads on PCB and it's shows near the working-one channel resistivity.
I try to put these transistor from a good channel and powering up my 2602 with one connected channel.
Oscillations stops power supply doesn't goes to protect mode, but i have +2.48V on output.
Ok, then i trying to put back Q32 to working channel, transistor tester shows that it's BJT-PNP with hFe=176 Ic=1,6mA Ube=658mV (Good ?)
When i put it back on previously working channel it shows on output -2,68V
Now two channels are bad.
UPD, extracting another one same as 2.A LLI from non working channel, i'll bring previously working channel back..
Home
Help
Search
Login
Register
