Meshtastic

OLED problem on T-beam boards

Hello everyone who has problems with T-beam boards. I read adjacent threads and see that I am not the only one with a problem.

I have 2 T-beam boards in my hands with the same problem - the OLED screen does not work after trying to solder the display board.

A deep analysis of the PCB shows that if the OLED is soldered inaccurately or if the Chinese PCB masters are defective, there are no contacts on the I2C SCK and SDA lines. In addition, these same contact lines go to another microchip. The lines on the PCB leading from the microcircuit to the contact covers are very thin and break off if soldered inaccurately. So this is not an OLED-display problem, but a T-beam board problem.

Later, I will provide a schematic diagram and a photo of problem points that need to be checked with a tester for the presence of contacts.

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Wut? :smiley: I want to see this inaccurate soldering job. Most of the solderings that I have seen on this forum are horrible and for most of the times there is only a problem between soldering iron and chair :slight_smile:

Here is a photo of a piece of a circuit that is very critical to the quality and accuracy of soldering. If you overheat or carelessly press on the soldering points, then very, very thin hairs of the contact lines can easily break. This can be seen under a microscope or by checking the contact with an Ohm meter tester.

Also, the 3.3V voltage contact may fail. It also needs to be measured with a Voltmeter. If there is no voltage on it or its insufficient level (1.2 … 2.8V), it is necessary to re-solder the display power contact to the 3.3V contact located next to it.

This is T-biam version 1.1

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My soldering job was horrible and I’ve done it repeatedly, adding and removing posts and wires. No flux, no sucker, just a really really hot iron and all three of my displays are fine. I guess I’ve been lucky!

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You are describing it as a problem with tbeam boards and as this is related only to i2c lines :smiley: If you rip a pad off due high temperature and inadequate force, then it is just your fault. It can happen on any board when you don’t know what to do… and yes, flux and a soldering iron with a good thermal capacity set to 300 C are your friends :slight_smile:
To be honest 2.54 pin headers are crazy big, I prefer 1.27 as these can be used for 2.54 just by removing every second pin.

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Hi all,
I also have an issue on one of my seven t-beams with the display. Everything was fine, but after desoldering the display. After that the 3,3V power supply pins are both on 0V.
Does anybody know where I can get the 3,3V somewhere else on the board?

Best regards
1984

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Try the following: Once again liberally moisten the 3.3V and GND pins with rosin flux. Solder these points so that the solder does not go beyond the edges of the pins. Rinse the soldered area well. The surface of the common metal is very close around the contacts. Inaccurate soldering may result in a short circuit. Check with an ohmmeter tester for short circuit to common ground of 3.3V pins or not. Contacts should not be short. If, after soldering the contacts, the voltage does not appear, then the power controller is damaged. In this case, you can find other 3.3V pins from other nodes.

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@ Der_Bear,

thanks for your suggestions. I did the tests you adviced and there is now short between 3,3V and GND Pins. And, there is even no connection between both 3,3V pins. So something (the pcb routing) seems to be damage due to the desoldering I did.

I couldn´t find the 3,3V regulator nor was I able to find alternative 3,3V supply points.
Do you know where the regulator is? Maybe I can exchange it.

T-Beam T22_v1.1 uses PMU AXP192 - the big IC on the left side on the shared picture.

Good hint, I checked the datasheet of the AXP192.

Do you have a shematic of the T-Beam T22_v1.1 pcb?
I´m searching which DCDC (1, 2 or 3) is used for the 3.3V of the LCD.

It is DCDC1, on the schematic marked as VCC_2.5V. DCDC2 is not connected, DCDC3 is powering ESP32, LDO1 is charging backup battery for GNSS, LDO2 LoRa and LDO3 GNSS

Top! Thanks a lot. I manage to get the 3.3V directly from the AXP192 and now my display works again as new.
Do you know if the eagle files are available somewhere?

This is how I did the wiring:

There are no official PCB or boardview files.

Good idea to rotate that SMA connector :slight_smile:

:slight_smile: yes, I rotated the connector to get a more slim overall footprint.
But still searching for “the best” case, to print it in 3D.

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after i rotate the sma on one of my boards, i will be designing a new case to accommodate the change.

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