FM3 Screen 'crash' and mix saves (0.97b)

[Xavier]

Re: power supplies- should we be using 7.5-9v dc with at least 1A (1000mA)? Any other specs to look for?

+ "centre positive" as you wrote above.

Not sure 7.5v is enough as the current go trough 2 diodes (-0.8V each) before the 5V comverter (7805 : that requires more than 6v on its input to deliver 0.3A).
I'll make specific voltage test this week.

Update :
While working (from home), i have a preenfm3 animated screen always on to make some tests (add capacitors, heat sink on the 7805 etc...).
I have some situations where the screen goes white but rarely before one hour or so of heavy animation, so testing takes a long time.
One workaround that seems to work well is a firmware fix. It detects when the TFT does not respond and reinit it (which does not impact the audio/midi threads).

[Xavier]

@ericd I made some tests, 7.5v is not enough.
With 7.5v as is, the pfm3 will turn on and makes sounds, but the whole circuit is powered by only 4.2v (instead of 5v).
It's possible everything works find except a slighty lower output volume, but i didn't make any long test at this voltage.

If you want to use a 7.5v power supply it's better to shortcut one of the 2 diodes, that are left and right of the dcIn jumper. Then it will be fine.

I'd be interested to know how is your TFT with the latest v0.99 firmware.
And if you saw any improvement with a new power supply.

[ericd]

Hi Xavier

I have just stuck with using the phone charger to power the Preen over USB as it works perfectly.

I did pick up a polarity converter though, so I can try a couple of different 9V supplies and report back.

Sorry if I caused any confusion by mentioning 7.5V. The only reason I mentioned this is that the metal case (used by Ardi in his build) has printed above the power supply "7.5-9V DC". I'll ignore the "7.5V" part of that and just use 9V adaptors.

Thanks for the update too!

[ericd]

0.99B

Just tested for 45 minutes with a different adaptor. It's centre negative but I used the polarity converter.
The 9V adaptor specs say:
INPUT 100-240V- 50/60Hz 0.3A
OUTPUT 9.0V=1.0A

Zero TFT inits! 

I'll run the test later too.

[Xavier]

Zero TFT inits! 

Good news ! 
Thanks for the feedback.

[ericd]

Ran the full 'TFT stress test' that you made as per the wiki.

Using the same 9v adaptor, again got the magic number 0.

Awesome work Xavier, troubleshooter extraordinaire! 

UPDATE: had a longer session last night, about 3 hours. During that time the TFT blanked 3 times,
The auto re-init worked twice, I had to do Menu Inst- button press for one.

EDIT- this part is incorrect after further testing (see below): each time was when I was in the Preset load screen.

Still a vast improvement over what I was getting previously. All the same I think I'll just go back to the USB phone charger as I can't see any benefit to using a 9V adaptor?

[served]

In my experience.

The best power for audio equipment comes from transformer based linear DC adaptor.

Switching adaptors also work and they work well. But if you have some issues with the unit the best refference to exclude power issues is a good transformer based linear power adaptor.

The good thing with transformer is the ground isolation. The best part of the linear regulator is low noise. You only need to convert 50Hz AC to flat DC and regulate it, the parts that are needed are simple and effective.

I dont usually use linear regulated poweradaptor. I use switching adaptors. But I always use it for refference if I have some strange issues. It helps to remove possible power issues from the eqasion.

USB power is always very problematic. And should be used as the very last resort.

You got your Preen from me assembled I believe. Let me swap it for you. I got a new patch of TFT screens that are very stable. Maybe it helps to swap it. I will take care of the back and forward shipping and it will go quick. A week to get it back.

[ericd]

Helpful as always, thanks @served

I have emailed you about this to discuss further.

Just had 5 TFT crashes in an hour so it is still an issue. And ignore what I said about only happening on the Preset loading screen- it's happening in editing screens now too.

[Toltekradiation]

hello Xavier,
i have a question about the TFT :
i ordered a model with the Q1 transistor, but the one i received today does not have it
it should work, as @forestcaver use one of this kind, but should i get another one ? how bad is that ?

[Xavier]

hello Xavier,
i have a question about the TFT :
i ordered a model with the Q1 transistor, but the one i received today does not have it
it should work, as @forestcaver use one of this kind, but should i get another one ? how bad is that ?

Hi,

All my TFTs work fine today with latest firmware, i have some without the transistor.
The only problem when there's no transistor is that the TFT backlight LEDs are powered directly from a GPIO of the STM32 which may limit the brightness.
Let me know if you notice any dysfunction.

[Toltekradiation]

ok,
thank you !