Synth-DIY Yahoo! Groups Archives

Poly 800 mk1 top segment of LED not lit

2012-09-19 by tombarndt

I've been searching the forum for this issue and haven't found it yet, the issue is the top segment/line of the LED display isn't lit. Everything else work great. I checked voltages feeding the displayboard and pin 5,and 6 are at around 2.8-3V and every other pin is showing between 5 and 6V. No obvious break in the yellow 14 wire cable and no obvious damaged traces. Wondering if anyone else has had this issue and if there are further tests to narrow the search. Possibly IC30 or IC31?

Re: [korgpolyex] Poly 800 mk1 top segment of LED not lit

2012-09-19 by Martin Ator

Have you tested the LED display itself?

I think it should be possible to light each segment on the LCD display using the diode test function of a digital multimeter or measure them as a diode.

If that segment of the display lights up from the diode test , then one of the parts driving it is faulty. Either an led driver IC or transistor is fault.

Apologies if you've already tried these.

From: tombarndt <tombarndt@...>
To: korgpolyex@yahoogroups.com
Sent: Wednesday, 19 September 2012, 21:33
Subject: [korgpolyex] Poly 800 mk1 top segment of LED not lit

I've been searching the forum for this issue and haven't found it yet, the issue is the top segment/line of the LED display isn't lit. Everything else work great. I checked voltages feeding the displayboard and pin 5,and 6 are at around 2.8-3V and every other pin is showing between 5 and 6V. No obvious break in the yellow 14 wire cable and no obvious damaged traces. Wondering if anyone else has had this issue and if there are further tests to narrow the search. Possibly IC30 or IC31?

Re: Poly 800 mk1 top segment of LED not lit

2012-09-20 by bimmerfan222

is it just one "8" display section or is it the entire group of "88 88 88" displays that are missing the top segment?

Hard to tell from your description and very pertinent information to help in the diagnosis.

--- In korgpolyex@yahoogroups.com, "tombarndt" <tombarndt@...> wrote:
>
> I've been searching the forum for this issue and haven't found it yet, the issue is the top segment/line of the LED display isn't lit. Everything else work great. I checked voltages feeding the displayboard and pin 5,and 6 are at around 2.8-3V and every other pin is showing between 5 and 6V. No obvious break in the yellow 14 wire cable and no obvious damaged traces. Wondering if anyone else has had this issue and if there are further tests to narrow the search. Possibly IC30 or IC31?
>

Re: [korgpolyex] Re: Poly 800 mk1 top segment of LED not lit

2012-09-20 by Tom Barndt

all across the three displays

On Sep 20, 2012, at 9:11 AM, "bimmerfan222" <bperkins211@...> wrote:

is it just one "8" display section or is it the entire group of "88 88 88" displays that are missing the top segment?

Hard to tell from your description and very pertinent information to help in the diagnosis.

--- In korgpolyex@yahoogroups.com, "tombarndt" <tombarndt@...> wrote:
>
> I've been searching the forum for this issue and haven't found it yet, the issue is the top segment/line of the LED display isn't lit. Everything else work great. I checked voltages feeding the displayboard and pin 5,and 6 are at around 2.8-3V and every other pin is showing between 5 and 6V. No obvious break in the yellow 14 wire cable and no obvious damaged traces. Wondering if anyone else has had this issue and if there are further tests to narrow the search. Possibly IC30 or IC31?
>