A question about Jtag Diodes

[Keihanzo]

Hi there,

I´ve jtagged some systems for my friends and myself and I have always used 1N4148 diodes for the installation and LPT reader because everyone said that they were OK. All the consoles are working fine so far, but Today I readed carefully the nandpro readme and it says that BAT41 are the prefered diode to use with the LPT reader (I know, it´s not the same thing as the Jtag wiring), being 1N4148 also usable but less eficient.
Because of this I have a doubt now... ¿Are the diodes that I used the most efficient ones or I am harming the GPU or Jtag port in the long run?

Thanks for reading

[Blackaddr]

Assuming you soldered everything properly without any accidental bridges, you can't harm the console with the wrong diodes.  If the diode can switch fast enough, you'll boot.  If the diode cannot switch fast enough, you'll get errors.

[Keihanzo]

Assuming you soldered everything properly without any accidental bridges, you can't harm the console with the wrong diodes.  If the diode can switch fast enough, you'll boot.  If the diode cannot switch fast enough, you'll get errors.

Thanks Blackaddr, very illustrative

 

[MastaG]

Which diodes switch faster then? 1N4148 or BAT41?
I did quite a few consoles for jtag and Zephyr motherboards seem to be most sensitive to switching problems causing the hack to fail followed by E79.
On these motherboards I first remove the solder from the holes with braid (MS' solder is really hard to attach a wire to), and replace it with my own solder after applying some flux (I have this can of flux wich I can spray onto the points (smells really nice)).
Then I solder my 1N4148 diodes with one leg into the jtag holes and the other leg a kynar 28g wire (as short as possible) to the rf-board and the other point.
I dont cut the legs of the diodes since I'm paranoide the heat of my iron will f*** them up causing them to not do the job.
Instead I apply hot glue all over the legs of the diodes and on the rf-board point (since I'm also paranoide the signal for wireless controllers will interfere with the jtag hack, lots of people report more errors when powering the xbox from a wireless controller).
After this the zephyrs will work most of time.
But still one in the 10 times it will fail to boot.
I get the feeling the jtag wires/diodes are really sensitive when it comes to XBR on Zephyr.
So if BAT41 handles the jtag hack better by switching faster I'm happy to give them a try.

[SuperKMK]

Which diodes switch faster then? 1N4148 or BAT41?
I did quite a few consoles for jtag and Zephyr motherboards seem to be most sensitive to switching problems causing the hack to fail followed by E79.
On these motherboards I first remove the solder from the holes with braid (MS' solder is really hard to attach a wire to), and replace it with my own solder after applying some flux (I have this can of flux wich I can spray onto the points (smells really nice)).
Then I solder my 1N4148 diodes with one leg into the jtag holes and the other leg a kynar 28g wire (as short as possible) to the rf-board and the other point.
I dont cut the legs of the diodes since I'm paranoide the heat of my iron will f*** them up causing them to not do the job.
Instead I apply hot glue all over the legs of the diodes and on the rf-board point (since I'm also paranoide the signal for wireless controllers will interfere with the jtag hack, lots of people report more errors when powering the xbox from a wireless controller).
After this the zephyrs will work most of time.
But still one in the 10 times it will fail to boot.
I get the feeling the jtag wires/diodes are really sensitive when it comes to XBR on Zephyr.
So if BAT41 handles the jtag hack better by switching faster I'm happy to give them a try.

I used 4148 like you did, but on a falcon and it never gave me any issues whatsoever... I dont know about the bat41 but the 4148 have 4ms switch time which is pretty darn quick.

I did all my solders, and then if I had any ends that were slightly elongated I removed those ends with snips once they were soldered in and then glued the wires to the board with hot glue, at the cooled solder points of the motherboard... I soldered mine to the underside of the board, easier access for soldering and cleaner look on the top of the board.

[Blackaddr]

@SuperKMK: switching time for 4148s is on the order of 4ns, not 4 ms.

I took a quick look at the datasheets for 1N4148 and BAT41.  The Fairchild 1N4148 has a capacitance of 4 pF while the BAT41 has a ST BAT41 has a capacitance of 2 pF.  Capacitance directly impacts switching speed.  Based on that, I would suspect the BAT41s to be faster.  I would assume other manufacturers to have similar values.

Zephyrs do seem to be temperamental.  If anybody has one that puts out a lot of E79, try using BAT41 and see if it gets better or goes away.

[B1N4RY]

I have also used 4153 diodes before (The ones that were originally used to build TA-level shifters), and they worked fine for me.

[Tiros]

BAT41 has a lower Vf, which is why its preferred.
Any switching type diode is plenty fast enough.