ADVANCED JTAG building for DUMMIES

[justplayin]

First off let me say that Chupy's Jtag guide is awesome...great detail, well put together...easy to follow..and because of this I have 3 working JTAGs.

So why am I posting ? I want to know a little more about the buffer chip and its need for external power.

The reason I am asking is that I really only use the JTAG on IRD models 3900 and 4700. I have soldered in DB9 pig tails that i nterface witht he JTAGs for easy ECM fixes. I also added a LED to the JTAG board for shits and giggles.

What I found interesting is that the JTAG will work in any power setting - 3.3v 5v or in the OFF position and the LED will light whenever Jkeys is funtioning.

So is it really necessary to have a cumbersome batterr pack added to the Jtag is I only intend to use it with these receivers ?

Is the buffer chip getting enough power from the IRD and Parallel port to protect the hardware from surges.

Thanks.

[skinerd]

I have a couple buffered jtags, one is an old one from the DTV days, it's 5v wall adapter powered. Both work fine. Some receivers, when I connect the old jtag, the power light on it comes on dimly, and it will read without being powered. Most receievrs, however, require that I power the jtag in order to read. Kind strange, I am sure there is a logical explaination, but I have not investigated it further.

[justplayin]

Wow, Skinerd...I feel honored, Big Fan Big Fan. You got me through my first DRD420RE Nozkt. So thanks.

Anyway...I really hate that battery pack in Chupy's guide...always fragile hard to get into a nice box. Would prefer to make one with an optional input for power.

But of course AC differs from DC and I am not an EE.

Obviously the chip is being powered via either the IRD or Computer port (at least on my set up.) But if I did run into a problem with another IRD I would like the option. Is there some where I could find info that would allow my to make this modification...so I dont blow up my Jtag, Ird or Computer ?

[skinerd]

Since you are using a db9 connector, pick the 3.3v up inside the receiver and run it out through a couple unused pins in the db9.

[send2r]

you can hook a j tag to an ird and it will not require a battery.... it never fails done 16 different irds and never failed......got plans around here somewhere.....
can post if interested let me find it it is around here somewhere...



share the joy were all in this together...send2r :cool:

[justplayin]

I appreciate all of your replys, but keep in mind that the jtag is getting power from both th eIRD and the computer. I know this because the led ligths when I attach the jtag to the IRD and when I run JKEYS.

So why would I need to tap the ird for 3.3v if it is already running. Am I running any risk of frying the ird without a supplemental power source?