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Sony IPS-360 GPS LCD Repair Guide

Just in case someone else would like to save one of these old GPSs from the trash, if it has the apparently blank LCD problem...

My unit had the symptom of no LCD display (like it was turned off), but the unit properly beeps when powered on, and the POS LED properly lights.

I found that the -5V LCD drive voltage had failed which causes the contrast to be turned off. The -5V inverter is on the small daughter PCB that is around the antenna connector on the lower main PCB.

Remove the battery cover.

Remove the battery cover gasket, then remove the 4 screws, then remove the back GPS cover

Remove the top PCB (4 screws) and carefully unfold the ribbon cable.

Remove the lower PCB (4 screws) and pry the PCB out from the light button side 1st, being careful not to mess up the button rubber pieces.

You will see a small daughter PCB under this PCB that surrounds the antenna connector. This small PCB also has the beeper on it. Unplug this PCB as this is the PCB with the -5V inverter on it.

Replace the two electrolytic SMT caps that are on either side (above and below) of the 8 pin SOIC labeled "7600" which is a switching power supply controller/inverter. I replaced the caps with SMT tantalums (remember Tant polarity markings are opposite of the AL electrolytics). Reassemble and test.

Regards to all who want to keep old stuff running :-) Craig

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cpu_nut
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Reply to
russ lavergne

Hi Russ, The first hopeful sign that the IPS-360 was not totally dead (although the display was 100% blank) was that, upon switching on, the beeper beeped and the POS LED came on. When I disconnected the GPS antenna (with the power off), there were additional beeps (I assume an error indication) when the switch was turned on, which I assumed was also a good sign that the main microprocessor was running.

My first troubleshooting started with the LCD controller which is the "Sharp 7930" on the back side of the PCB that the LCD crystal is on. Search on "EN2778C.pdf" to get the data sheet. As of Nov 2005:

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I saw that the various TTL (0 to 5V) clocks were running on the Sharp chip which is a hopeful sign.

I then measured that the -5V was absent on pin 36 "Vee". All LCDs require a negative voltage on the LCD crystal which is the voltage that provides the contrast. Then I traced the -5V back to the small daughter PCB through the ribbon cable, and the small connector to the daughter (small) PCB.

On the daughter PCB, I recognised the inverter chip "7660" from previous experience. I was familiar with the 8 pin inverter chip "7660" and how it uses the capacitors (one is a charge pump, and the other is the negative V filter) so I just knew that these were likely causes of failure for aluminum electrolytic capacitors. The main issue here is that Al electrolytic capacitors are often a weak point in a design. With an O-scope I saw that the 7660 was oscillating (a requirement for a charge pump to operate), but its output to the PCB trace that went to the Sharp 7930 was at zero volts with just a bit (maybe 0.1V) of the 7660's square wave from the oscillator. From experience I knew the electrolytics were the most likely problem especially since the 7660 itself was switching / oscillating. There is also a small diode in the circuit around the 7660, and I verified that it was good with a VOM / diode tester. I replaced both capacitors with tantalum capacitors since I know that this type will last longer in this circuit.

I think just about every IPS-360 has failed in this fashion from the little that I have read online, and I hope this information will keep a few alive for history.

I hope that helps, Craig

Reply to
cpu_nut

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