Korg t3 boot problem no lights

Pasali · Post by **Pasali** » Mon Oct 04, 2021 9:35 pm

Wow! What electronic level, I am impressed! It is fortunate to have this kind of experts. Best of luck with the repair.

Invader32 · Post by **Invader32** » Thu Oct 07, 2021 10:32 am

I did as you said and shorted pin 13 of IC45 to ground while measuring pin 10 and it behaved like it was supposed to, the output went from 4.5v to 0 and then back up again when I removed it. But the keyboard still did not boot and nothing happened on the screen, just the usual lines were there . I replaced the capacitors after the keyboard stopped working because at first I thought it must've been some capacitor related issue because they hadn't been replaced so I ordered a kit and replaced them. But the keyboard still had the issue and didn't work. Also I would like to mention that I suspected the reset circuit because when I was changing the capacitors I noticed that the 50v 1uf capacitor was shorted open and I was using my multimeter to check by continuity,(I know they can't be checked accurately like this) but the replacement was giving me readings like a capacitor is supposed to as it charges from the multimeter' s voltage. That's why I thought the reset circuit might have something to do with it.

T3owner · Post by **T3owner** » Thu Oct 07, 2021 11:05 am

OK - based on what you determined, it appears that the problem is not related to a reset issue.

If you are located in an area where the humidity is high, especially in a coastal region with "salt air", some corrosion can develop and connector and other contacts might be an issue. One thing you could try is to reseat the ROMs in their sockets.

Invader32 · Post by **Invader32** » Thu Oct 07, 2021 11:31 am

You mean to remove the rom chips and then put them back in?

T3owner · Post by **T3owner** » Thu Oct 07, 2021 2:17 pm

Invader32 wrote:You mean to remove the rom chips and then put them back in?

Yes, although you might be able to only partially unseat the chips and then push them back in place. Such contact wiping can help if there's a poor connection. Power should, of course, be off, and care taken not to bend or misalign any pins.

Invader32 · Post by **Invader32** » Thu Oct 07, 2021 4:31 pm

I reseated them but still nothing, I have no idea what could be wrong enough to cause it to not boot. Tell me if there's something else I can check and see. I really want this to work.

T3owner · Post by **T3owner** » Thu Oct 07, 2021 10:46 pm

Have you tried self-checks? The following includes two test modes that aren't documented in the service manual...

Korg T-Series Self-Check Modes
------------------------------
Display OS ROM version number at upper left corner of display:
Press Number button 0 (lower row, "FINE") while turning T power on.

Initiate test mode as per Service Manual:
Press Number button 0 (lower row, "FINE") and PROG A button while turning T power on.

Initiate test mode that includes MIDI check:
Connect cable between MIDI-Out and MIDI-In.
Press Number button 0 (lower row, "FINE") and COMBI button while turning T power on.

Initiate test mode that includes PCM and Card memory testing as well as MIDI check:
Connect cable between MIDI-Out and MIDI-In.
Press Number button 0 (lower row, "FINE") and PROG B button while turning T power on.

Note: Accessing the last two modes above is not revealed in the Service Manual. These modes are available with OS version 29 ROMs, and possibly earlier versions.

----------------------------------
The lack of normal boot might mean that none of the above will work. However, let us know if there is any indication of a response.

Also, do you have access to an oscilloscope?

Invader32 · Post by **Invader32** » Fri Oct 08, 2021 10:06 am

I've tried self checks before and they didn't work because it isn't booting up, and these combinations don't give any response either. I don't have an oscilloscope, they aren't easily available here where I live. Also I wanted to ask, above the removable chips there is a solder pad marked high and usually they have 5volts when the keyboard is powered on but the one above the removable chip is low 0 volts is this normal?. Also if there are some voltage checks I can verify on the cpu or ram chips please let me know.

T3owner · Post by **T3owner** » Fri Oct 08, 2021 11:02 am

Invader32 wrote:I've tried self checks before and they didn't work because it isn't booting up, and these combinations don't give any response either.

As I mentioned, I thought that might be the case.

I don't have an oscilloscope, they aren't easily available here where I live.

That's unfortunate. Checking for clock signals, etc., might help with diagnosis.

Also I wanted to ask, above the removable chips there is a solder pad marked high and usually they have 5volts when the keyboard is powered on but the one above the removable chip is low 0 volts is this normal?.

Besides the "HIGH" marking near one ROM socket, the other socket is marked "LOW". A data word is 16 bits long, which can be formed from two eight-bit bytes. One ROM contains the high bytes, the other the low bytes. The board is marked to indicate which ROM goes in each socket.

Also if there are some voltage checks I can verify on the cpu or ram chips please let me know.

I'm sorry, but DC voltage checks (other than power to chips) tend to be of minimal value in troubleshooting digital circuits. I can only echo, as Pasali suggested, that you recheck your previous work. Perhaps someone else will have further advice.

Best of luck.

Invader32 · Post by **Invader32** » Sat Oct 09, 2021 9:36 pm

I guess I'm done with this one then, thank you both for your support and help.

Cheers.

slooky · Post by **slooky** » Fri Nov 05, 2021 8:11 pm

I was sort of having the same problem with the x3,,,I turned the power on and there was nothing. I had to hold enter and down button and then push power button and it turned on.