| Electronics > Repair |
| Keithley 2602 repair need help! |
| (1/1) |
| smaultre:
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. |O UPD, extracting another one same as 2.A LLI from non working channel, i'll bring previously working channel back.. |
| Zucca:
I am sure you already looked here: https://xdevs.com/fix/kei2425/ It is a K2425, but it could be a good source to narrow down your problem. |
| smaultre:
The product lines 24xx & 26xx have different schematics.. |
| smaultre:
What is the part type? 2n3906 ?? |
| smaultre:
https://www.eevblog.com/forum/repair/keithley-2602-dual-smu-repair/ DONE! |
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