Strange worrying behaviour after display replacement..

[andyfox]

Hello guys,

I just replaced the display of my Emulator II, since the original one was very old and almost unreadable.
I did it following the instructions I found here on the forum along with the links.
I followed the procedure on this blog, seemed to me quite easy for my soldering and electronic knowledge..
http://www.nattvard.com/cmi/e-mu-emulator-ii-lcd-screen-change/

The Emulator II is also equipped with HXC Floppy SD Card Reader since last year, I've had no problems with it.
Everything seemed to went well, but just after a few hours using it in the studio, all the red led lights went on.
Sometime it happens to me that the Emulator get stuck when she doesn't like some midi data.
But this time the problem is back even when I switch it off and on again.
So I disconnected the power, yesterday, for one night. Trying now to boot it, the first boot went ok.
Today I just discovered the LCD is showing messy chars as well.
What could it be? I am desperate. Very worried about my Emulator II I don't want to destroy it.

I bought this blue MIDAS screen:
http://it.farnell.com/midas/mc21605a6wd-bnmlw/lcd-2x16-neg-stn-white-led-b-l/dp/2063158?CMP=i-bf9f-00001000

and this hex inverter:
http://it.farnell.com/texas-instruments/sn74ls04n/ic-hex-inverter-74lso4-14dip/dp/1106072?CMP=i-bf9f-00001000

Any help would be much appreciated.. thank you guys.

Andy

I am attacching some photos to show what's happening.
Thanks again

[andyfox]

*UPDATE!*

I was able to solve the problem "ALL RED LEDS ON"...

Man. There was a screw stuck under the Emulator motherboard!!!!!

Must have been there for years, from the previous owner.
The screw was not belonging to the Emulator II.
There must have been a contact between the external case and the board, thus the leds on!

Concerning the problem about the strange characters on the display...

The problem appears when I am using the Emulator for some hours, when it starts to get hot 
In case I have to switch it off and then on, the strange chars starts to populate the display.

Then I switch it off again, pull off the power cable.
I wait for 1 minute, then I put on the power cable again and power-on the Emulator.
The problem is gone. 

Any clue?
Thanks for your help guys

Andy

[HideawayStudio]

*UPDATE!*

I was able to solve the problem "ALL RED LEDS ON"...

Man. There was a screw stuck under the Emulator motherboard!!!!!

Must have been there for years, from the previous owner.
The screw was not belonging to the Emulator II.
There must have been a contact between the external case and the board, thus the leds on!

Concerning the problem about the strange characters on the display...

The problem appears when I am using the Emulator for some hours, when it starts to get hot  
In case I have to switch it off and then on, the strange chars starts to populate the display.

Then I switch it off again, pull off the power cable.
I wait for 1 minute, then I put on the power cable again and power-on the Emulator.
The problem is gone.  

Any clue?
Thanks for your help guys

Andy

This is actually a common issue which I've reported a fix I came up with before but perhaps not on this site.

The LCD timing on the EII is marginal and although it just about works with older HD44780 compliant LCD modules, many of the modern equivalents have faster timings.  

This often manifests itself by showing nothing, a solid bar or garbled characters on the bottom line of the display.  The top line is always fine with a new display fitted.

The fix I came up with several years ago has helped a number of other owners to make their new displays work so this is definitely worth a try....

FIX: Solder 4.7NF metal film capacitor between pin 1 (Ground) and pin 6 (Module Enable) on the LCD module header.

This works by slightly lengthening the Enable pulse to the display.