Synth-DIY Yahoo! Groups Archives

Thread

Power on issue with Poly-800

2011-07-04 by 7yash

Hi all, just got a second-hand, quite battered Poly-800.

As you expect, it has the lost or randomized patches issue.

It also has an issue with the power supply: it won't turn on with the external power supply. I managed to turn it on with the internal battery leads connected to a 9V battery initially.

Now, what it does is it will sometimes turn on (sometimes not) and only for a few seconds on internal battery - anything from 2 to 10 seconds. This is, of course, annoying, since it's not even enough to play back the factory patches in Tape Mode.

I have searched a lot on the forums including this one, have replaced the Q1 transistor with a new PNP. I have yet to try changing the nearby Zener diode (9/10V).

I just bought a multi-meter (it's analog) and a continuity tester, have plenty of replacement parts, also downloaded the schematics and read everything on this forum concerning battery issues.

Have been going through the service manual testing procedure. Currently, even with the VR1 trim-pot adjusted to the max, there doesn't seem to be enough voltage.

Any guidance would be thoroughly appreciated.

Yash

Re: Power on issue with Poly-800

2011-07-04 by 7yash

For now, I have left the power supply with the jack on it's own, but when I tested it with an external 9V output, pin 6 on the first set of connectors does not give 5V but rather 9V so something is definitely wrong there. If somebody knows what to look for, let me know.

I have temporarily hooked a 9V external supply to the battery leads by extending the latter and soldering to the extensions.

2 fingers burnt but still soldiering on :P

Yash

--- In korgpolyex@yahoogroups.com, "7yash" <josh.nursing@...> wrote:
>
> Hi all, just got a second-hand, quite battered Poly-800.
>
> As you expect, it has the lost or randomized patches issue.
>
> It also has an issue with the power supply: it won't turn on with the external power supply. I managed to turn it on with the internal battery leads connected to a 9V battery initially.
>
> Now, what it does is it will sometimes turn on (sometimes not) and only for a few seconds on internal battery - anything from 2 to 10 seconds. This is, of course, annoying, since it's not even enough to play back the factory patches in Tape Mode.
>
> I have searched a lot on the forums including this one, have replaced the Q1 transistor with a new PNP. I have yet to try changing the nearby Zener diode (9/10V).
>
> I just bought a multi-meter (it's analog) and a continuity tester, have plenty of replacement parts, also downloaded the schematics and read everything on this forum concerning battery issues.
>
> Have been going through the service manual testing procedure. Currently, even with the VR1 trim-pot adjusted to the max, there doesn't seem to be enough voltage.
>
> Any guidance would be thoroughly appreciated.
>
> Yash
>

Re: [korgpolyex] Power on issue with Poly-800

2011-07-04 by billmeirelles@uol.com.br

1 - Have you checked your power supply unity?
2 - Have you tried with a diferent power supply?
3 - Have you tried to resolder the power supply connector in the poly 800 pcb?
4 - Have you checked the battery wiring? If the positive wire is in contact with
ground the power loss will be huge, even when the power supply is in use.
5 - Have you give the pcb an isopropyl alcohol bath using a tooth brush? It can
help you see clearly to trace any broken solder or bad parts, also it helps to avoid
ground loops created by conductive dust.
6 - Don't set VR1 to max as it can get something fried, let it in the middle position for
now and when you get the poly to powerup properlly than you adjust it as the service
manual describes.

Em 04/07/2011 16:49, 7yash < josh.nursing@... > escreveu:

Hi all, just got a second-hand, quite battered Poly-800.

As you expect, it has the lost or randomized patches issue.

It also has an issue with the power supply: it won't turn on with the external power supply. I managed to turn it on with the internal battery leads connected to a 9V battery initially.

Now, what it does is it will sometimes turn on (sometimes not) and only for a few seconds on internal battery - anything from 2 to 10 seconds. This is, of course, annoying, since it's not even enough to play back the factory patches in Tape Mode.

I have searched a lot on the forums including this one, have replaced the Q1 transistor with a new PNP. I have yet to try changing the nearby Zener diode (9/10V).

I just bought a multi-meter (it's analog) and a continuity tester, have plenty of replacement parts, also downloaded the schematics and read everything on this forum concerning battery issues.

Hav e been going through the service manual testing procedure. Currently, even with the VR1 trim-pot adjusted to the max, there doesn't seem to be enough voltage.

Any guidance would be thoroughly appreciated.

Yash

Re: [korgpolyex] Power on issue with Poly-800

2011-07-05 by Josh Nursing

Thanks for replying. Now I have soldered the external power supply output to extensions made to the battery wires. It's working. I managed to transfer the factory patches through a wav file played on my computer.

The sound is huge. I barely dare bring it to 6 as the sounds with resonance will blow my speakers.

I have a video here: http://www.youtube.com/watch?v=uZeL_43Dpo0

I checked with two different 9V power supplies and none would work. I haven't unsoldered the jack though.

The battery wiring is fine.

I brushed the PCB with a toothbrush and alcohol yesterday, and didn't notice anything out of the ordinary.

Good point about VR1, I will check all the servicing procedure and the trimpots again now that the power is fine (most probably my 9V battery had become weak).

Yash

On Mon, Jul 4, 2011 at 5:49 PM, <billmeirelles@...> wrote:

1 - Have you checked your power supply unity?
2 - Have you tried with a diferent power supply?
3 - Have you tried to resolder the power supply connector in the poly 800 pcb?
4 - Have you checked the battery wiring? If the positive wire is in contact with
ground the power loss will be huge, even when the power supply is in use.
5 - Have you give the pcb an isopropyl alcohol bath using a tooth brush? It can
help you see clearly to trace any broken solder or bad parts, also it helps to avoid
ground loops created by conductive dust.
6 - Don't set VR1 to max as it can get something fried, let it in the middle position for
now and when you get the poly to powerup properlly than you adjust it as the service
manual describes.

Re: [korgpolyex] Power on issue with Poly-800

2011-07-05 by billmeirelles@uol.com.br

You are welcome...

Bill Meirelles

Em 04/07/2011 21:16, Josh Nursing < josh.nursing@... > escreveu:

The sound is huge. I barely dare bring it to 6 as the sounds with resonance will blow my speakers.

I have a video here: http://www.youtube.com/watch?v=uZeL_43Dpo0

I checked with two different 9V power supplies and none would work. I haven't unsoldered the jack though.

The battery wiring is fine.

I brushed the PCB with a toothbrush and alcohol yesterday, and didn't notice anything out of the ordinary.

Good point about VR1, I will check all the servicing procedure and the trimpots again now that the power is fine (most probably my 9V battery had become weak).

Yash

On Mon, Jul 4, 2011 at 5:49 PM, <billmeirelles@...> wrote:

1 - Have you checked your power supply unity?
2 - Have you tried with a diferent power supply?
3 - Have you tried to resolder the power supply connector in the poly 800 pcb?
4 - Have you checked the battery wiring? If the positive wire is in contact with
ground the power loss will be huge, even when the power supply is in use.
5 - Have you give the pcb an isopropyl alcohol bath using a tooth brush? It can
help you see clearly to trace any broken solder or bad parts, also it helps to avoid
ground loops created by conductive dust.
6 - Don't set VR1 to max as it can get something fried, let it in the middle position for
now and when you get the poly to powerup properlly than you adjust it as the service
manual describes.