Lcd issues also bankstick question

[TafterT]

Hi folks,

I have just finished wiring up my Midibox Sid and optimized PSU,switched it on and everthing was working ok untill after about an hour when now  the lcd has an intermittent fault, there is a line missing from the top line of characters, this comes and goes ,i have checked for shorts etc and cant seem to find anything ,i am using the 4685 pic and the lcd is wired up for 4 bit operation ,is this problem likely to be a dodgy lcd module or could it be a problem with the core ?.

The other issue i have is the core doesn't seem to accept patch updates to the bankstick i have managed to get the vintage presets onto the bankstick using Sysexbox ,it only worked once now i cant seem to change the preset patches.

Thanks for looking !! 

[nILS]

Welcome aboard TafterT! ;D

Do your voltage regulators get really hot after a while?

As for the uploading of the patches: Try to fiddle with some different block sizes and most importantly pause times after each block.

[TafterT]

Hi ,

The voltage regulators on the Sid modules dont seem to get hot or even warm neither does the one on the psu board !,one thing i have just noticed is the trim pot for lcd luminocity doesn't seem to be doing anything !

[TK.]

Very strange! Check the LCD connections and core module solderings, something seems to be wrong here.

Especially the missing pixel line shows, that this isn't a software or configuration issue, as the HD44780 protocol doesn't allow to access the pixels directly (only characters can be sent).

It cannot be excluded, that you damaged the LCD due to a wrong connection - did you change anything during build-up?

Best Regards, Thorsten.

[TafterT]

Hi,

I forgot to mention previosly to wiring up the lcd module properly i had wired it up wrong and when switched it on it got warm and didn't work, so that might have damaged the internals slightly ,also when building the core the only changed i made to the  module was to leave out the voltage regulator and bridge rectifier as i was using the optimized psu .

[TK.]

I forgot to mention previosly to wiring up the lcd module properly i had wired it up wrong and when switched it on it got warm and didn't work

Ok, I fried many (4?) LCDs this way in the last (20?) years - there is no way to fix it; it has to be replaced.

Best Regards, Thorsten.

[TafterT]

Ok ,thanks for the help much appreciated !

[zgba]

One word about LCD backlight adjusting. I can't do it too, but I guess the cause is too high voltage on T1's base. In my case it was at least about 0,7V. Isn't it too much for T1? So maybe we should change P1 to ~22k and R4 to slightly more - for example 2,2k?

[Matrix12x]

the same pot does nothing for me as well