Acer G236HL, constant restart after energy star logo.

[check12]

I repair pro-audio gear so have test equipment just very little experience with monitors beyond obvious basics.

Acer G236HL monitor is about 10 years old and uses the S230HL main board (analog & digital inputs).

I already replaced the board electrolytic caps about 6 months ago which fixed the monitor taking longer and longer to turn on and it's been fine again until now.

The monitor will power on, show acer logo, show energy star logo, then it should show blank black screen, then show video or "no signal" if no source plugged in.

It now restarts constantly after the energy star logo.

PSU load tests fine, 12v,5v,3.3v,1.8v rails all test fine, cables are seated properly, cant find any defective diodes etc, etc. I also ran through the troubleshooting flow charts to see if there were any pointers there and all checks out ok, BQ2 pin3 & BR26 pin1 are low, PWM signal is showing on BR4, backlight is working etc.

I've a feeling that this fault may be familiar to some of you guys who fix monitors regularly and any help or info about the start up sequence that can save me time on further testing would be well appreciated.

Service manual attached ...

[check12]

Re: Acer G236HL, constant restart after energy star logo.

Here's a high resolution photo of the board.

[lotas]

Re: Acer G236HL, constant restart after energy star logo.

You may have a problem in the external power supply (capacitors), when the load drops, the output voltage drops, the Power button (leakage in the button itself) or the firmware may be stuck.

[check12]

Re: Acer G236HL, constant restart after energy star logo.

Hi lotas ... just played about again with psu on electronic load tester and doesn't seem to drop at all when load drops, ripple is about 20mv pk/pk and it holds within 0.4v of 19v to over 3A.

Power button I'll test again first chance (I've only got the psu here just now).

I've got a feeling that it may be firmware but have no idea how to confirm.

I'd love to find more info on the start up sequence so i could find out what is supposed to be happening circuit wise when the monitor constantly restarts.

[lotas]

Re: Acer G236HL, constant restart after energy star logo.

If there are no options, then here are dumps for your motherboard (0171-2271-3734), you need to program U5 - Pm25LD020 through the programmer and do not forget to save your dump.

[check12]

Re: Acer G236HL, constant restart after energy star logo.

Thanks for that ... it will be a last resort option though.

I haven't programmed anything for years , I have a couple of programmers but I don't think they support U5. I read that CH341A is cheap and does a good job?

Anybody know what should be happening in the signal sequence after the energy star logo when the monitor is incorrectly restarting or any other pointers for finding out what isn't happening?

[check12]

Re: Acer G236HL, constant restart after energy star logo.

At what point do you decide that re-programming the eeprom is necessary? ... e.g. what are common symptoms?

Is what I have detailed above a common symptom of a corrupt eeprom?

[lotas]

Re: Acer G236HL, constant restart after energy star logo.

Well, if all the supply voltages are in order and without ripples, the buttons do not short, there are no short circuits anywhere, then what remains is either the firmware is damaged or the processor itself, what do you have to lose, reprogram the firmware to spi flash (keeping your own) on the programmer and make sure the firmware is working or no.

[check12]

Re: Acer G236HL, constant restart after energy star logo.

Ok lotas I will have to order a CH341A kit and try it. I'll let you know how it goes. Thanks for your help ...

[check12]

Re: Acer G236HL, constant restart after energy star logo.

While waiting for the programmer ... I tried heating the board a few degrees with a low powered hair drier around U5 and the main processor... and after a few seconds of heating it boots properly to the "no signal connected" screen.

I think I will try re-flowing the IC pins ...

[check12]

Re: Acer G236HL, constant restart after energy star logo.

Nah reflow didn't work ...

But after heating for a few seconds now the monitor always starts properly.

I am using a hair dryer so the heat is over a wide area but it is centred over U5 ... which I think is the eeprom.

Anybody recognise this faults behaviour?

[check12]

Re: Acer G236HL, constant restart after energy star logo.

Can someone confirm that U5 in the attached schematic picture is the eeprom chip?

[lotas]

Re: Acer G236HL, constant restart after energy star logo.

This is the SPI Flash where the firmware resides. Replace with a new one, preprogramming it.

[check12]

Re: Acer G236HL, constant restart after energy star logo.

Ok sorry I didn't see you had already confirmed this above.

Can't easily get the MX25L2026E IC here what alternatives can I use?

[lotas]

Re: Acer G236HL, constant restart after energy star logo.

Try W25P20, W25X20,... (x25x20), any brand on 2M-BIT.

[check12]

Re: Acer G236HL, constant restart after energy star logo.

These are hard to find ... can find x25x** IC's but not x25x20.

Can I use other memory sizes?

[lotas]

Re: Acer G236HL, constant restart after energy star logo.

The closest one is 25x40 (4M-BIT), try it.
Look on aliexpress, there you will find yours as you need.

[check12]

Re: Acer G236HL, constant restart after energy star logo.

I just re-flowed ALL the larger diodes, regulators etc. in the area I was heating and now it seems to be back in service ...

Thanks for all your help anyway lotas!, the ch341 will no doubt come in handy for something else & I have learned some things.

If I had to buy IC's from Aliexpress I would just have bought a full pcb for £25: https://www.aliexpress.com/item/32691442447.html