Motorola C975 (ex-"3") on T-Mobile?

[trellis]

Hi All!

I recently bought an Unlocked Motorola C975 off eBay, because I needed a UMTS-capable phone for Japan. (They have no GSM in Japan, so UMTS is required for roaming. )

The phone was originally on the "3" network, and still contains all of the "3" branding. I put my T-Mobile SIM in, and it seemed to work fine on 2G or 2.5G. I took the phone into central London to check UMTS operation, but sadly it didn't work. As soon as the phone "sees" a 3G network, it is unable to make or receive calls. When outside 3G coverage areas, everything works fine. I also noticed that in central London, the phone frequently lost all coverage altogether, while the O2 phone in the other pocket was rock-solid.

I read on the T-Mobile site that they cannot guarantee correct operation of 3G on ex-"3" phones, but if the phone is unlocked, surely it should work?

My question really is: is my C975 faulty, or is it true that ex-"3" phones don't work on T-Mobile's 3G network?

The supplementary question is: will this phone roam on the Japanese (NTT DoCoMo) UMTS network?

Many thanks in advance!

[Junglizt1210]

I am guessing you have T-Mobile pay as you go. I have never used T-Mobile, but I know that O2 and Orange don't allow access to their UTMS, while Vodafone and 3 pay as you go's do allow access. That's where my guess stems from.

As far as I know, it's not an issue of being able to use the 3G in the UK... you need to check with T-Mobile if they have roaming agreements in Japan.

For example, my Orange SIM card is a pay as you go in the UK..... and it can't use Orange's uk 3G network... (CS told me they need to issue a special SIM card for a fiver), but it can roam perfectly fine on UTMS in Hong Kong.

You need to check that T-Mobile have roaming agreements with Japan basically. According to this (http://www.gsmworld.com/roaming/gsminfo/roa_gbme.shtml) it does.

If you want, go to a T-Mobile store, and tell them you're travelling to Japan, and that you need to make sure roaming is set up. Let them know that you have a 3G phone as well.

[trellis]

Thanks for that!

Sorry, forgot to mention that it's a contract SIM, but I called CS anyway. They said that my SIM is already 3G-enabled, and it *should* have worked! The only explanation they could come up with was that the network was too busy at the particular time I tried it. Plausible, I suppose.

I will give it another try next time I am in a T-Mob 3G coverage area and report back.

However, it sounds like it should be OK in Japan, even if it doesn't work in the UK. If Wikipedia is to believed, NTT DoCoMo invented the W-CDMA protocol that was adopted for UMTS, so it ought to bl**dy well work :-)

[trellis]

Hurrah! After some extensive Googling and experimenting, I have got to the bottom of this problem. I post the solution here for the benefit of others who may be experiencing this problem.

Basically, it seems that the C975 does not like it when both a 2G and a 3G network are available at the same time. When this happens, all sorts of things start going wrong, including loss of network altogether, rapid fluctuating between 2G and 3G, dropping of calls or inability to make calls, inability to find a network etc.

The trick is to force the phone to use the 3G network only - go into Settings, choose "Network" then "Network Setup", and change the "Band" setting from "Automatic" to "WCDMA2100".

The problem is that this is very difficult to achieve when the phone can see both a 2G and 3G network, as it keeps dropping back to the home screen when you're in the middle of making the changes. I actually had to wait until I was out of 3G coverage to make the change. If you are quick enough, though, this might not be necessary.

Another snag with this is that, obviously, when you move out of 3G coverage, you lose all network access. Unfortunately, the C975 does not have an option to force 2G-only - the only options are "Automatic" (use whatever is available), "GSM1900" (the American GSM band) or "WCDMA2100" (3G only).

I am not sure if this problem is specific to "3"-branded phones, or to T-Mobile contract SIMs, but I have two such C975s and they both exhibit this behaviour on my T-Mobile SIM.

Hope this is useful to someone!