PreenFM3 display going blank

[Kyg]

Hi,

I built a PreenFM3 a few weeks ago and have been very happy and impressed with it!
Wonderful synth engine, interface, and a fantastic variety of filters! Thanks for a great synth!

The one thing that is bothering is that the display occasionally goes blank. I know that this is supposedly due to noisy power and changing to a different USB power supply did improve the situation. I also know that a function was already implemented in the firmware that automatically resets the display when it goes blank. This works sometimes but often I still have to reset the display manually by pressing MENU and -.

My observation is that the display never or only very rarely goes blank when the PreenFM3 doesn’t receive any MIDI information. I can have it on that way for many hours and the display stays perfectly fine. But when the unit plays the display does go blank often. The frequency of blank screens seems to depend on the load on the synth engine (how many notes, voices, active sound channels etc.)

I’m no techie and I could be completely wrong, but to me the dependence on synth engine load might indicate that the cause isn’t noisy power. BTW, none of my other synths and effects etc. have ever shown any signs of power issues.

I doubt that my solder connections to the display are weak and I’ve tried numerous different USB power supplies and power outlets.

I'd be glad for advice how to solve this!

Thanks,
Phil

[Xavier]

I thought this problem was gone 


You said it seems to be related to midi activity.
Both DIN5 and USB ?
Don't you think it can be realated to Display activity that follow midi note ?

Have you tried to use the sequencer with all level metter on ?
Let it play (without midi data) with the display showing all level metters and see if it's stable.

When the TFT does not change, no data is sent to it. So it's stable.
The CPU only send data when the display has something new to show.
From all the tests i've made (and i've made a lot), the problem was some random corrupted data (due to external noise), that puts the TFT in a bad state.

The TFT displays is today very stable on the preenfm3s i have. (I had to tweak many parameters in the firmware).
Is your TFT soldered ? or do you use a  connectors between the main board and the TFT ?

Let me know if you found something,
I can make a firmware with slower Data transmission to the TFT, to see if that makes change.

Xavier

[Kyg]

Hi Xavier,

Thanks for your help!

I ran the Sequencer on 4 tracks today with level meters on and the display went blank frequently (requiring MENU and -, auto detection didn’t work)

As soon as I stopped the Sequencer the display became perfectly stable again.

Btw, the firmware file I installed was the current v0.107. However, the Preenfm3 displays v0.106.

Regarding the TFT pins, I soldered the 4 top pins but used a connector on the row of bottom pins.

Phil

[Kyg]

Hi Xavier,

if you have any more insights about possible solutions for the blank TFT or anything else I could try to diagnose what’s causing it, please let me know!

Thanks,
Phil

[Xavier]

Hi Kyg,

The most likely reason is some noise on the CPU to TFT lines.
If your soldering is clean on the TFT connector, that can be the connector itself. Try remove the TFT and to push it back.
You can also try to change the connector (i know it's a real pain), or to solder directly the TFT without connector.

I finally found time to compile a firmware with a slower (4 times slower) communication between the CPU and the TFT.
I attached 0.107s (s for slow  )
I hope that will prevent the TFT from receiving corrupted data.
So before doing anything you can try this firmware and see if that makes a difference.

Xavier

[Kyg]

Thanks so much for your help at solving this, Xavier!
I will check with the new firmware and let you know!

Phil

[Kyg]

Hi Xavier,

I tested the modified 107s firmware. My impression is that the slower update rate of the TFT hasn’t improved the issue and that the display goes blank just as often as it did with the regular firmware.

I guess I will have to try to replace the display connector and solder it directly.

But, in any case, the issue doesn’t really affect the usability of this great little synth!

Thanks,
Phil

[Kyg]

Hi Xavier,

I have one more question about the display going blank:

Whenever this happens, pushing MENU and + always gets the display back to normal. The CONFIG setting to auto detect sometimes works, but eventually there is always a moment when it doesn’t work. That’s when I need to reset the display manually.

Wouldn’t it be possible to fix the auto detection to always work?
Or could the reset simply be automatically done at regular intervals?

Thanks,
Phil

[Xavier]

The autodetect is the preenfm3 that regularly asks the TFT if it's still alive.

If the TFT does not reply, then a TFT reset is triggered.

I think there are some cases where the TFT is blank but it still replies that it's alive.
Sorry, there's not much i can do.

But this blank screen does not occure anymore on any on my preenfms.
It was a real problem on early firmware.

[Xavier]

If you have time, could git a try to firmware v1.05.
https://github.com/Ixox/preenfm3/releases/tag/v0.105

This one does not have "TFT backlight" feature that send Pusle Width Modulation to the TFT to adjust the led intensity.
Would be interesting to see if it's more stable without it.

Thanks

[Kyg]

Great! I will try that firmware and report back.

Thanks,
Phil

[Kyg]

Hi Xavier,

sorry it took me a while to report back!

I did some extensive tests with Firmware 105, but the display also blanks out with this firmware.

This time, I used a stop watch to check how frequently the display goes blank. With four MIDI tracks playing four voices in the PreenFM3 the display went blank far more frequently than with just one MIDI track.

I remain a little skeptical about the TFT connectors causing this. But I will, at some point, resolder the TFT in the hope that it solves the problem.

I could be wrong, but my impression is that the display only goes blank with display activity from external MIDI data but not from display activity when using the PreenFM3 knobs and buttons. If that is so, would it be reasonable to think that a PERF screen without the oscilloscope would not go blank?

Thanks,
Phil

[Xavier]

I did some extensive tests with Firmware 105, but the display also blanks out with this firmware.

Too bad.
But it's good to know.

I could be wrong, but my impression is that the display only goes blank with display activity from external MIDI data but not from display activity when using the PreenFM3 knobs and buttons. If that is so, would it be reasonable to think that a PERF screen without the oscilloscope would not go blank?

Didn't you say that the sequencer playing alone without any external midi also crashed the screen ?
"External midi" ? Both USB and Din5 midi jack ?

[Kyg]

Yes, that’s true. I forgot that I tested it before with the internal sequencer and also got a blank display.
I just don’t remember ever editing any parameter and the display going blank at the same time. I guess that’s why I thought that changes on the display from editing may not result in a blank display.

I haven't used the USB Jack for MIDI in my setup.

I guess I’m still hopeful that there may be a solution to the blank display other than me having to resolder the TFT.

Thanks for all the attention you have already given this!

Phil

[cokosha]

Hi, Kyg!
Any news about your problem?