Dear Daniel: According to your results, I think the internal RF path got something wrong. Please check power pin of the RF switch U7606 first (See GPS..jpg). The 3.0V voltage should be measured while turning on GPS. Then, check Vcont Pin (See GPS.jpg) is low (under 0.2V) while using internal antenna. After the above items are checked, Please plug the external GPS antenna and measure the Vcont. High means that the switch is normal (But if your external path is OK, I think the Vcont is always high). If not, I suggest replace a new component on your Neo.
Of course, the current monitor IC U7605 may the reason to make the path switch is abnormal. Please measure the voltage drop (15mA*6.8Ohm=0.1V or higher depending on your external ant) between Pin2 and Pin3 (See GPS.jpg) while plugging GPS external antenna and Pin 1 is high. If the answer is yes, U7605 works. You may just change the one RF switch to fix it. I have to check the parts are in stoked in our lab. If you need them, just give me a response. Thanks. Best regards, Shawn ________________________________ From: Daniel Willmann [mailto:[EMAIL PROTECTED] Sent: 2008/3/5 [星期三] 上午 09:30 To: SHAWN_LIN (林孝光) Cc: [email protected]; DKAY_CHEN [陳南廷]; TIM_LEE (李國平經理); ALLEN_CHANG (張吉隆) Subject: Re: GPS issues on GTA02v4 Hello, On Tue, 4 Mar 2008 09:13:25 +0800 <[EMAIL PROTECTED]> wrote: > I am the hardware engineer dedicate to RF parts. After reading your > statement about this issue, this issue may be caused by bad > connection of internal GSP antenna. Some tests should be performed on > your Neo. I will also send you two antennas. One is internal and the > other one is external. thanks for offering that, but no need. I already have an external antenna here and I have a couple Neos from which I can take internal antennas. > 1. Replace the new one on your Neo and check signal quality (In > open-sky, the TTFF is less than 50s) > If the result follows my expectation, the reason for this issue may > be repeat de-assembling to damage the RF cable of the internal GPS > antenna. I already tested another (known good) internal GPS antenna which didn't work either. My multimeter says the cable on both antennas are okay. > If not, I think you can do the next test > > 2. Plug the external antenna in our Neo and check the signal quality > > If the GPS is normal, I think the RF switch circuit (ESD sensitive) > is complete break-down. Yeah, did that and it got a fix in ~40s, so the GPS chip itself is working. > I will send you these two antenna as soon as possible. If any > question, let’s discuss together. If you have an idea what I can do to test the RF switch circuit let me know. I do have a soldering station and know how to use it. :-) Regards, Daniel Willmann
<<attachment: GPS.JPG>>
