Kurzweil pc3x booting problem

Hi,
I have a used Kurzweil pc3x, which I bought few months ago to “study” VAST synthesis. It started to freeze during bootup after I connected it to PC via USB. Now it freezes on “Initializing scanner…” and boots up after I have turned it on and off for several times without any additional cables. Sometimes it shows error code “db1f”. I have managed to update it now to latest os and clean the few easily accessible cable pins, but the problem is still there. I would be thankful for any kind of suggestion to fix the problem. It seemed that the VAST world is an interesting way to keep me busy for many many years I would like to bring the instrument back to fully working condition.

thank you for your time,
Martin

Does the synth boot up and operate normally without external connections?
Did you look up what error code “db1f” means, or Google that on Web?
Do you have the manual? If so, check the section on connecting it via USB, or to an external PC.
Does the PC require some specific Kurzweil driver installed to detect synth on USB? Did you check in Windows settings under connected Devices to see if it shows the synth listed? If not, disconnect USB cable, restart synth, then with both instruments powered on, reconnect the (Plug-n-Play) USB cable. What happens then? Is it shown in the Devices, or Audio lists? :thinking:

Thank you for helping me!

Does the synth boot up and operate normally without external connections? - No, no difference -

Did you look up what error code “db1f” means, or Google that on Web? - I tried and even asked from Kurzweil (they did not answer), but have not found the meaning -

Do you have the manual? If so, check the section on connecting it via USB, or to an external PC. - I have, I have checked, no help -

*Does the PC require some specific Kurzweil driver installed to detect synth on USB? - No, but I have installed Kurzweil software with everything they had there for this synth -

Did you check in Windows settings under connected Devices to see if it shows the synth listed? - It recognizes the synth only if I have managed to boot it up after several attempts -

If not, disconnect USB cable, restart synth, then with both instruments powered on, reconnect the (Plug-n-Play) USB cable. What happens then? Is it shown in the Devices, or Audio lists?* - If it boots up after several on/off switching then everything seems to work fine.

I checked the manuals on line and It doesn’t also have a SCSI port, as some instruments of that era did. Such an option can produce very similar symptoms as you describe, if not properly configured.
I’ll check for that error code too. Unfortunately I have no experience with Kurzweil and only vaguely remember the mentions of the VAST synthesis thing.

Service manual is online, and running diagnostics is described. See https://www.manualslib.com/manual/1114872/Kurzweil-Pc3x.html
When you follow that procedure at power on, we need to know what diagnostic test is running and failing, producing the error code, then what options it gives you on screen at that report stop.

Also you didn’t mention if you performed a factory reset on it yet. Internal memory would be wiped and reset to factory configs during that. It’s good to try on an acquired used instrument of considerable age.

I can enter into diagnostics (under bootloader menu) only if I have several times switched the instrument on and off, so the instrument seems to freeze even before to option to enter the bootloader menu. If it finally manages to boot, I can run the tests, did also loop for 10 times and there are no errors.

I have performed factory reset several times. I also did repeat OS update. No change in behaviour.

Currently I am thinking about to disassembly everything, clean all the connectors. Would that be a good idea?

P.S. I also did run diagnostics for the sliders and buttons before and after cleaning the sliders with aerosol spray. After cleaning, the sliders and buttons work perfectly.

You just about answered your own question -“ only if I have several times switched the instrument on and off”.

This is a typical case of failed electrolytic capacitor(s). these capacitors kind of behave like car batteries; they contain an oxide layer between the two poles that create the separation of the two “plates”. Old Electrolytic capacitors can break down that oxide layer and become a short circuit - but applying power may be able to partially restore that oxide layer and remove the short. That is what you experience right now.
Solution - re-cap the engine board and the PSU I’m afraid …

Thank you all for your time and suggestions. Fortunately, it turned out that the problem was easy to solve. While I was looking inside the instrument to find bad caps or count these for change, I noticed that some screws that hold the central logic board where loose and some even missing. Somebody was perhaps unscrewing them before and did not put back properly. These screws seemed to link the board with main grounding. I put some new screws and tightened the old ones. Problem solved!

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