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#1612 - 06/07/15 10:46 PM
No display, only two lan leds issues
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Japhar Member
Carpal Tunnel
Registered: 10/19/10
Posts: 9876
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No display, only two lan leds issues P5 Fault Finder Pinout, Or, with power sources Often you can also find the faulty circuit by measuring the Ohms value, (Thank you to Johnny_B for publishing it)All the best about hardware/support from Johnny_B, link : http://jb8a8f8.comhttp://jb8a8f8.nl
Attachments
Fault_finder_pinout_P5.jpg (51 downloads)
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#1614 - 06/07/15 10:51 PM
Re: No display, only two lan leds issues
[Re: Admin]
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Japhar Member
Carpal Tunnel
Registered: 10/19/10
Posts: 9876
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Rev. M/G or ? mainvoltage information. More info, see this topic, Rev M/G voltage source information
Note: If the voltage are fine, but by Ohm values are the 1.2/2.6/3.3 values to low, others are fine then it is most likely a cpu issue.
TIP: One of my cases, No front LED, but two LAN LEDs are On. Other symptoms without simcard always 5v at Vcc / Rst / Clk / IO. when the print on / off and immediately on again it runs. Voltage P5 values are correct, Display connector second row 3.3/5.0/3.3/3.3/2.7/0.0.. (normal = 3.3/5.0/3.3/3.3/3.3/3.3..). 4 large caps replaced / replaced Q8 did not help. After replacing the U18 - TL7702A the problem was solved.
TIP: One of my cases, Ohm value looks healthy, but ampere value too high. volt measurement, 2.6v = 1.9v 1.3v = 0.890v
After removing the U7 R283 0 Ohm resistor, U7 side = 2.6v, other side = 1.9v, 1.3v = 0.890v but the Amp consumtion is fine now.
In my case a bad connection U24 LG. Check the connection U24 LG pin 2 to the U25 pin 4 / HG pin 14 to the U24 pin 4.
TIP: One of my cases, Symptoms, Ohm value u6/3.3v was 37 U7/2.6v ohm value was 800. So both wrong, others were fine.
Removed U6 R118, U6 side okay. Removed U7 R283, U7 side okay.
At the beginning I thought it was a problem on the 3.3v circuit, but in the end it was a diode problem U7. Diode D6 leaked a little, after replacing the problem was solved. By heating the U7 sector I saw that the Ohm value rises.
TIP: 5v circuit If you have a problem with the 5v circuit, see this drawing.
Or read on the topic, DM_800_REV_L_Dead_only_eth
U23, 24 25.. Updated, More information added and changed some voltages.
U6..
U7..
U7/P5 pin 2 test for short circuit (Ohm measurement).
Attachments
dm800-5v-circuit-information.jpg (14 downloads)U23-24-25-oct-2k11.jpg (12 downloads)U6-2012.jpg (8 downloads)U7-Schematic-DM800-v3-300511.jpg (46 downloads)Measure-2-6v-circuit.jpg (44 downloads)
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