Hi Guys,
I'm sure the solution is on here somewhere if someone could point me to the right place that would great.

I am new to the Iphone. I bought a secondhand 3gs that was working perfectly except for LCD had failed(dim screen).
I have replaced the LCD, the Digitizer and the charging dock.
have tried to restore on Itunes - result not eligable for restore.
have tried greenpoison and pwnage.
Any help appreciated
Thanks

You mention a lot in your post but aren't really specific enough that we can help too much:

1) Error 3194 / Device not eligible for requested build is due to SHSH files. If you don't know what they are, read the link in my sig or google it. You will need SHSH on file for any version of iOS that isn't current if you want to restore to it, as you can only restore the 3GS to versions of iOS that Apple is still signing. Without the SHSH, you will have to upgrade to 5.0.1 (or whatever version of iOS is current at the time of you restoring) or you will get the 3194. Use TinyUmbrella to determine if Cydia has any SHSH on file for you. If not, you can use iFaith to attempt to pull partial SHSH blobs for your existing running version of iOS, but that only works if the phone isn't bootlooped without firmware.

2) You mention a blank IMEI and blank S/N, but don't mention anything about the baseband. Usually, blank IMEI and no S/N are signs of hardware failure. They can also cause your phone to not successfully be able to restore. Let us know what revision baseband is on your phone, you can usually find out with f0recast.

Depending on the behavior, it could be that the baseband bricked during a flash operation, in which case successfully flashing it to an upgrade with baseband included MAY make it work again. That said, I am hesitant to provide too much troubleshooting as I don't really know enough about your current situation to recommend anything. Let us know the following:

1) What iOS revision was on the phone before you started messing with it?
2) What iOS revision are you attempting to flash onto the phone?
3) What baseband is the phone running?
4) Are you attempting to unlock?
5) What (if any) version SHSH do you have on file with Cydia or locally?

Let us know and we should be able to help.

Thanks for responding n1ckn4m3, I will check SHSH as soon as I can.

1) What iOS revision was on the phone before you started messing with it?
Stupidly didn't check before i started?

2) What iOS revision are you attempting to flash onto the phone?
I think 4.3 was the only one that was acceptable.

3) What baseband is the phone running?
Don't know
4) Are you attempting to unlock?
I will be happy just to have worling phone - at least to start with.

1) OK, try using f0recast to determine if any version of iOS is running on the phone. This is important because you may be able to pull the required SHSH out of it.
2) At this point, the only version of iOS that Apple is signing is 5.0.1 for the 3GS. This means that if you want to restore 4.3, you would need to have an SHSH on file locally, or have one available on saurik's server that you could retrieve with TinyUmbrella.
3) OK, use f0recast for this as well, it's only important for when you unlock, but it can add resale value, etc., so if we know now I can give you better advice.
4) OK, understood.

This is what I would do:

1) Make a custom 5.0.1 IPSW, electing to block the baseband update using the latest redsn0w (0.9.10b3)
*Note: If you are 100% certain you never want to unlock, and you're not interested in selling the phone at any point, you can allow the baseband update.
2) Use redsn0w or iReb to put the phone into "Pwned DFU" mode
3) Shift/Option click on 'Restore', and point it to the No_BB firmware you made in step 1 (or the custom firmware you made with the baseband)
4) Let it restore and you should be ready to go, jailbroken on iOS 5.0.1.

Thanks for your help.
so - iPhone3gs is stuck in recovery.
f0recast does not recognise device at all.
Tiny umbrella V5.10.06 finally gets into recovery loop where the iPhone has been for a while.
The only restore version which I could get it to except was iPhone2,1_4.3.3._8J2_...e.ipsw (custom)
result:-unable to find
gBdevlist
fs_mount
fs_unmount
Bs_load_file

When i try to put on charge the iPhone does not show Imei or serial but I do have record of them.
I would like to unlock, So shall i continue and follow your last recommendation do steps 1) to 4) ??

Most likely, if your IMEI is showing blank, the baseband itself is shot and even if you get ultrasn0w on the phone, I don't believe it's going to work to make phone calls.

At this point, I don't think flashing to 5.0.1 will fix your problem -- since you'd be blocking the baseband update (in order to unlock) it has a only a markedly slim possibility of fixing your issue. The steps will still work, however, if you want to give it a shot.

Most important though is that if the IMEI is blank after the flash, nothing will make the radio work...

So it didn't work but hey at least I tried. Seem crazy situation I'm sure Apple have the means to correct this.
Anyway thamks for your help.