I have dell laptop D600m. I have a charger for it but the charger does not work properly meaning that it can power the laptop but does not charge the battery of the laptop.

I opened the charger and saw the circuit of the charger and found a problem in a transistor at the end the circuit which two legs are connected but the 3rd one is free. The transistor no is Dallas 2501+0447D3+170AA. I live in peshawar Pakistan, I searched in different electronics shops but could not find anywhere.

How can I replace that transistor with some other which is available in shop easily. I bought two other chargers but after some time they had the same problem.


closed as off-topic by PeterJ, Nick Alexeev Dec 31 '15 at 19:48

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the repair of consumer electronics, appliances, or other devices must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired. See also: Is asking on how to fix a faulty circuit on topic?" – PeterJ, Nick Alexeev
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  • 3
    \$\begingroup\$ No e-mail. You post here, you read here. \$\endgroup\$ – stevenvh Jul 14 '12 at 16:38
  • \$\begingroup\$ You don't say whether the transistor is actually faulty - did you try soldering the 3rd leg back in place? \$\endgroup\$ – Oli Glaser Jul 14 '12 at 16:40
  • \$\begingroup\$ A not-soldered pin may happen once in a while, but if that's the reason why it doesn't charge they should have caught that in manufacturing test. \$\endgroup\$ – stevenvh Jul 14 '12 at 17:00
  • 1
    \$\begingroup\$ According to this link the IC is not a transistor, but a 1-wire memory chip. \$\endgroup\$ – m.Alin Jul 14 '12 at 17:01
  • \$\begingroup\$ @m.Alin - Yes, I also found that. I.e. I deduced it because I found 2502, but not 2501. \$\endgroup\$ – stevenvh Jul 14 '12 at 17:03

Like also m.Alin says the DS2501 is a memory IC. It's no longer available, replaced by the DS2502, which appears to have twice the memory.

The DS250x use a 1-wire serial protocol, where data and power share the same pin, so that there are only two of them required:

enter image description here

(Why they don't put it in a 2-pin TO-92 is beyond me. That's an existing package.)

  • 2
    \$\begingroup\$ (Why not in a 2-pin TO92): Because all 2/3-pin one-wire chips have this pinout. This one does not need power (beyond the 1-wire parasitic power), so the power pin is NC. \$\endgroup\$ – Wouter van Ooijen Jul 15 '12 at 8:01

Since your charger and the other two didn't work, it is virtually certain the laptop, not the chargers, is at fault. Especially given stevenvh's point that what you saw is fine for that part.


It can be usefull, i tried to test it like a transistor, so I found this information: http://www.laptop-junction.com/toast/content/inside-dell-ac-power-adapter-mystery-revealed

  • \$\begingroup\$ Do not just post a link to a off-site resource. Explain the solution here. \$\endgroup\$ – Martin Zabel Dec 30 '15 at 13:38
  • \$\begingroup\$ If you just supply a link, and the link breaks, your answer will be useless for all EE.SE users. Therefore you only get negative feedback on such an answer. If you sum up what you have found in your link so that it can be used directly, you'll get better feedback. \$\endgroup\$ – Ariser Dec 30 '15 at 17:31

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