Emulator II+: new display problem

[cowboy]

Hello, I've just upgraded my EII+ with a Lotharek Drive and a new display (MIDAS MC21605A6WD-BNMLW). I've also replaced the IC25 with a SN74LS04N Hex Inverter, but the screen often shows strange character sequences....   Any ideas? Thanks for your support!!!

[dr.c]

One first rule is to never, when possible, change a few components at a time.
For example, change the drive first, and see how it works, etc..., otherways you will never know what's wrong !

[Wolfram]

And check the order of the Display connection.

[Electro disco club]

I have thé same issue with LS, SN etc.

I've just replaced thé PSU, wondering if it Will work with a good 5v adress?

I Will check and test with thé midas screen.

[Electro disco club]

Sorry, the midas screen is always mad

[cowboy]

Thanks for your feedback. Can you recommend a display?

[alka]

I am using this Midas display with no trouble. Perhaps you have an issue in your Scanner circuit - I've had similar issues with odd characters but it was tracked to a bad IC. I forget which one at the moment... will look when I get a chance.

[HideawayStudio]

Sorry, the midas screen is always mad

Might be worth trying my usual mod for new displays on EII....  (I'm not saying it will work in your case but its worth a try)

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.

[Kalem]

And check the order of the Display connection.

Yep always check the order first.

[Sandrow]

Installed same display on board and had the same issue on different menu pages.

Solved with a Ceramic 33pF capacitor between pin 1 and 6.
I'm testing it before soldering properly but at the moment no issues at all.

Cheers.

[Electro disco club]

Great,
It works well !

Underground music by night 

Thanks

[alka]

Just wanted to update this as I had replaced my display with the MIDAS one as per the instructions here: http://www.nattvard.com/cmi/e-mu-emulator-ii-lcd-screen-change/ and the IC25 change did nothing to correct the timing issue. Unfortunately neither did Dan's solution with the 4.7nf. However seeing that Sandrow had success with the same display with a 33pf capacitor from pin6 to ground i tried a 22pf (closest i had on hand) and it worked! Just thought I'd confirm that this lower value cap solution works across multiple machines.

[dfiorucci]

Did you remove the other fixes or was this in addition to the other fixes of the resistor and IC25 change?
Thanks,
Dana

[alka]

just a one-to-one replacement of the display as instructed here: http://www.nattvard.com/cmi/tag/midas-mc21605a6wd-bnmlw/ and one 22pf capacitor between ground and pin 6.

[dfiorucci]

Just replaced my display with this one.
<http://www.newark.com/midas/mc21605a6wd-bnmlw-v2/display-alphanumeric-16x2-white/dp/03AC3420?CMP=AFF-CJ-6455582-Newark%20Product%20Catalog&source=CJ&CAWELAID=120185550003512238>

Had to change IC25 with a SN74LS04N Hex Inverter and file a small clearance in the circuit board to fit the display in also had to slightly open up the mounting holes.

Looks great