Dead pixels or...?

[bitrex]

LCD display having issues:

http://tinyurl.com/jovnnra

Dead pixels, corroded/dirty ribbon cable contacts, or something else?

 

[whit3rd]

On Saturday, April 2, 2016 at 12:03:51 PM UTC-7, bitrex wrote:

LCD display having issues:

http://tinyurl.com/jovnnra

Dead pixels, corroded/dirty ribbon cable contacts, or something else?

Doesn't look like dead pixels, more likely a logic corruption. The wrong letter, maybe just
a weak bit in whatever holds the program memory. Start looking at the power supply
(hey, it's a WEAK bit, could just be low battery).

 

[Jeff Liebermann]

On Sat, 2 Apr 2016 14:47:35 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Saturday, April 2, 2016 at 12:03:51 PM UTC-7, bitrex wrote:
LCD display having issues:

http://tinyurl.com/jovnnra

Dead pixels, corroded/dirty ribbon cable contacts, or something else?

Doesn't look like dead pixels, more likely a logic corruption. The wrong letter, maybe just
a weak bit in whatever holds the program memory. Start looking at the power supply
(hey, it's a WEAK bit, could just be low battery).

I agree. Check the power supply voltage.

My guess(tm) is that the display has a COB (chip on board) that has a
broken wire bond and the display needs to be replaced. Just touching
the blob of epoxy is sometimes enough to trash a wirebond and missing
pixels cannot be produced by data errors between the synth and the
display.

1601 displays are quite common and cheap, but not with EL
backlighting. If you're going to replace it with an LED backlighting
version, you'll need to:
1. Check the thickness of the display as they do vary and may not
fit.
2. Disarm, disconnected, and possibly remove the EL high voltage
power supply.
3. Find a way to power the backlighting. Some run on 5.0V, some
bring out just the diodes and need a series resistor, and I ended up
with one that wants 4.4VDC.

I thought it was easy, but it took me several evenings to replace the
display:
<http://802.11junk.com/jeffl/Korg_DSS-1/>


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jon Elson]

bitrex wrote:

LCD display having issues:

http://tinyurl.com/jovnnra

Dead pixels, corroded/dirty ribbon cable contacts, or something else?

Yes, that looks like a ribbon-zebra-LCD contact problem. Carefully
dismantling the assembly, cleaning the LCD and ribbon contacts and then
getting it back together is risky, but then it isn't working now, so not
that much to lose.

Jon

 

[bitrex]

Jon Elson <elson@pico-systems.com> Wrote in message:

bitrex wrote:

LCD display having issues:

http://tinyurl.com/jovnnra

Dead pixels, corroded/dirty ribbon cable contacts, or something else?
Yes, that looks like a ribbon-zebra-LCD contact problem. Carefully
dismantling the assembly, cleaning the LCD and ribbon contacts and then
getting it back together is risky, but then it isn't working now, so not
that much to lose.

Jon

Thanks for the reply. The original LCD was very old, and it
literally crumbled in my hands as I attempted to disassemble it
from the board to clean the contacts.

Fortunately, I managed to find a lot of 3 unlit LCD displays on
eBay that look like drop in replacements for the original - they
use the same SMT OEM Hitachi display controller in a similar
package, and even the PCB layout is very similar. The date code
on the original board looks like 1986, these are from the early
1990s.

$3 plus shipping for the lot. Seems like a much easier solution...

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