Xbox TSOP recovery

[scrappysphinx]

Hi all

So I have a 1.0 Xbox that I flashed the tsop with evox, it uses a 1mb bios but I chose a 256kb and now I have a black screen. I tried the 3 wire trick to try booting from different banks of the tsop but got nowhere.

I know I can just install a modchip but I don't have one to hand and I'd like to try and restore the tsop.

So I did some digging and came up with an old tutorial about wiring up a 27c2001 EPROM as a custom modchip which once booted can be disconnected and the tsop reflashed. Now I've programmed the chip with evox 2.6 bios and wired up the 29 wires as instructed in this page

https://web.archive.org/web/20151009063717/http://www.xbox-scene.com/modchips/ownmod_diagrams.html

It's not pretty but it does boot and is working fine however this is where I'm failing. According to what I've been reading once booted into evox you need to disconnect pin 32 a link on the motherboard that piggybacks off pin32 and pin16 to disable the eprom allowing the tsop to be flashed.

I have disconnected the connections as advised but I can't reflash, evox tells me unknown device/ chip not writeable

Anyone have any tips as to what I can try?

Sent from my ONEPLUS A3003 using Tapatalk

 

[grantek]

Those instructions are pretty confusing but here's roughly what's going on:
- Pin 16 is ground, but it's also used as a "low" signal
- Pin 32 is Vcc but it's also used as a "high" signal
- In the first picture, you wire up /OE, /CE, and /WE to pin 16 on the new EPROM to hold it enabled
- In the lower pictures you link one of the pins of the TSOP to pin 32, which is Vcc, presumably to disabled the TSOP by holding the TSOP's /OE or /CE high.

It's not clear what you're doing next, it sounds like you're moving /OE or /CE on the TSOP from Vcc (chip/output disabled) to ground (chip/output enabled).

However the EPROM chip is still also in its enabled state. If you're also disconnecting pin32 on the EPROM then that's to disconnect it from power and remove it. That's not usually the way you deselect chips though.

So some things to try:
- If you're only moving a connection from pin32 to pin16 on the TSOP without doing anything to the EPROM, then go back and look for instructions to disable the EPROM (ie. if disconnecting EPROM pin32 works, do that)
- If you've done everything as instructed, my only other thought is that maybe the EPROM is being powered through one of the other pins, and is responding to the Device ID request (which is a special form of read). If that's the case, I'd suggest leaving pin 32 on the EPROM connected to pin 32 on the TSOP, and using the /CE pin (pin 22) to enable or disable the EPROM. To do that, hook up a switch or something so that you can flip EPROM pin 22 between pin 16 (EPROM enabled) and pin 32 (EPROM disabled)

 

[fordav1]

It might be easier to just get a new flash ROM and re-program it with the correct image. You can get a cheap EPROM programmer for less than $50 and a TSOP socket adapter and program the chip directly, then remove the old one and drop in the new one. Problem solved.
If you can't do the work yourself, I'm sure there are plenty of people in the UK who can do it for you.
It's also much safer than messing around with loads of wires like you are doing now.

 

[scrappysphinx]

Hi guys, thanks for the tips. I do have a couple of programmers but i didn't have the tsop adapter for them. Anyway, this board ended up dead. The eprom chip contacted some pins on the motherboard while it was powered and i saw smoke coming from the MCPX chip. It's no big loss to be honest, plenty more xbox motherboards out there

 

[fordav1]

heh! well after I saw the mess of wires I figured it was never going to work again anyway
the TSOP adapters are available on the other bay for just a few dollars.
Lesson learned... to anyone reading this.... next time get some advice and do the repair the right way and you won't kill it. You're lucky it wasn't something rare and expensive ;-)