R-JTAG (R-)JTAG Troubleshooting once past POST 0x2E

Martin C

VIP Member
Jan 10, 2004
Scotland, UK
This guide is for people who are getting past POST 2E on R-JTAG, or JTAG installers in general.

If you are NOT getting past 2E on R-JTAG, this guide is NOT for you. Instead, the problem lies with the R-JTAG chip configuration.

If you attempt to boot an R-JTAG (or even JTAG) and you receive E79 (1033), it means the JTAG payload which is delivered via TDI/TMS (J2D2.1 and J2D2.2 respectively) has failed.

There are several causes of this error. I'll go through them in the order of probability:

1. SMC Configuration vs JTAG setting.

There are two accepted JTAG wiring methods which are used in J-Runner:
i. Normal (DB1F1 and RoL) - AUD_CLAMP NOT ticked in J-Runner.
ii. AUD_CLAMP (DB1F1 and AUD_CLAMP) - tick AUD_CLAMP option in J-Runner prior to building xell and image.

Your JTAG wiring MUST match one of these. It's advisable to stick with one or the other throughout the process so you don't get confused. I recommend AUD_CLAMP for all HDMI consoles, as you can have sporadic issues with RoL such as erratic lights on your RoL board, random config resets, etc.

2. JTAG component/wiring issues.

If your JTAG wiring is bad/wrong/missing, you won't boot a JTAG image. Period. Therefore, it's important to check both continuity of source/destination points and diodes.

To check continuity:

QSB users can easily check continuity by using the image below:


The QSB is of the older variety but the concept is exactly the same: Set the left switch to 'ON' and the right switch to '0'. Check continuity between the pairs of same colour circles. Also check to ensure the different colour circles have no continuity between them. To test the 330/470 switch, set the switch to the middle (330/470) and choose a jumper setting accordingly. Checking resistance between the BLUE circles should result in a 330 or 470ohm reading, depending on which one you checked.

To test the diodes, check this image:

(image taken from http://www.allaboutcircuits.com/vol_3/chpt_3/2.html)

On JTAG wiring, the cathode is the end directly linked to the destination point from the QSB. So in the QSB image above, the orange and green circles are on the ANODE side of the diode. Simply put your meter onto 'ohms' as above and ensuring you have the correct orientation of probes, check as per above. Diodes are one-way components, so you should have continuity when the red probe is on the anode and black on cathode, but nothing the other way around.

Finally, it goes without saying that any broken traces to the JTAG points will stop it from booting.

3. TDI/TMS connection to the GPU.

This is the least likely cause of your problem, especially if you've eliminated the first two.

It's entirely possible for any console to not have a good connection to TDI/TMS, even from factory. The GPU JTAG header is not used in retail units so won't be put through QA. There's a basic test you can carry out.

With a multimeter set to 10kohm max (or auto-ranging on kohm), put one probe on J2D2.1 (TDI) and the other on ground. Do NOT have the PSU connected - it's not needed. Note the value. It should be around 1.5kohm. Do the same with J2D2.2 (TMS). Again, it should be the same.

If these values or off, or even if you've exhausted all other options, there's a chance you have a bad GPU. I've only seen this once in the hundreds of JTAGs I've done. The only fix was to replace the GPU.

Please leave thanks if this was useful :)

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