Electronics guru’s in here please.

eLbot · 5 Sep 2006 at 01:34

Ok, long story short; I’m a complete novice but I’m being forced to make the following in order to read the eeprom from my Thinkpad T41 laptop and recover the supervisor password:

I’ve had trouble finding a supplier that will do small quantities but came up with the following:

http://www.fastcomponents.co.uk/index.php

I’ve found the correct resistors but I’m a little confused as to whether the Zener diodes from pack 10:

http://www.fastcomponents.co.uk/product_info.php?products_id=36

are suitable as they are of the BZX55 rather than 79 specification, having no real idea what that specification means and being unable to find it elsewhere I’ve come here. I have a rudimentary understanding of what a Zener diode is and from my understanding there shouldn’t be a problem. But I’m not really willing to just go ahead and find out either. So whilst this is a massive long shot; any help guys?

Adam_151 · 5 Sep 2006 at 08:03

Close enough for jazz, as they say, (I'd have thought, for what you are doing with them)

Fensta · 5 Sep 2006 at 09:04

Umm, flash the BIOS? :confused:

monkeyspank · 5 Sep 2006 at 10:13

can;t you just reset the bios?

squiffy · 5 Sep 2006 at 10:17

No, laptop passwords are stored in a non volitile BIOS area, usually encrypted...so if you forget password basically knackerd (needs to be sent back) Not like a desktop board, simple BIOS reset removes password.

At least laptops have more security protection (also HD passwords as well)

Bear · 5 Sep 2006 at 10:40

The BZX55 will be a 5.5V zener when used as a voltage reference so no use if you need a 7.9V

Sputnik II · 5 Sep 2006 at 10:45

The Zener diodes in that diagram are 0.5 watts rating, so as long as you get something equal to or larger power rating would be fine. something like the BZV85C 5V1 would do you.

Edit: your going to buy a complete multipack with all those values for just 2 diodes?

If all you need is a couple of zeners and resistors etc. I'll send them to you FOC if you want, save you having to buy silly amounts you wont use.

Sputnik II · 5 Sep 2006 at 11:02

Bear said:
The BZX55 will be a 5.5V zener when used as a voltage reference so no use if you need a 7.9V

The Zener's in the diagram are 5v1 not sure where you get the 7.9 from :confused:

BZX55 is the range number it would be followed by some extra digits and letters to state voltage i.e. BZX55C5V1 which would be a 5.1 volt unit.

Dr.EM · 5 Sep 2006 at 11:27

Mighty expensive for 500mw zeners :eek:

. I know a UK supplier that will do any quantity at 4p a piece (BZXC5V1). It might well be a competitor, email in trust. You still need to pay postage if this in under £25exc vat (£3.50 or so for postage, next day usually)

Sputnik II · 5 Sep 2006 at 11:34

Dr.EM said:
Mighty expensive for 500mw zeners . I know a UK supplier that will do any quantity at 4p a piece (BZXC5V1). It might well be a competitor, email in trust. You still need to pay postage if this in under £25exc vat (£3.50 or so for postage, next day usually)

Because 4p is cheaper than 1.9p :confused:

The £3-99 is for 21 packets of 10 of each voltage value isn't it?

Anyway, I've offered to send him some for free if he wants to Email me a postal address and provided he only needs a few.

Dr.EM · 5 Sep 2006 at 11:51

Oops, read that wrong. That must be like a starter kit or something, I thought it was 10 of any of those values for £4. Nevermind, looks like you've got it covered if your sending some.

eLbot · 5 Sep 2006 at 12:42

Fensta, monkeyspank -

Unfortunately guys, no, this is the –only- way to recover the supervisor password and retain all data stored under the HDD under the same password at this stage – save having hypnotherapy to recall the password.

Sputnik II -

Yes I was going to buy those entire multi-packs just for two diodes and two resistors. The price really didn’t bother me because the alternatives made this look cheap and more practical than buying a few hundred of the same plus I could grab PCB at the same time. Although the idea of being able to make resistor people and animals sounds good; I would be massively appreciative if you had some of those you didn’t need. Email on the way

Thanks.

Bear · 5 Sep 2006 at 13:09

Sputnik II said:
The Zener's in the diagram are 5v1 not sure where you get the 7.9 from

BZX55 is the range number it would be followed by some extra digits and letters to state voltage i.e. BZX55C5V1 which would be a 5.1 volt unit.

I was in a hurry and read the 79 specification in the opening post.