Kurzweil K2000S shuts down

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Kurzweil K2000S shuts down

Postby ALaMothe » Sat Jan 12, 2019 3:18 am

Hi all, new to these forums! I do home recordings as a hobby, have been for all my life. I've owned a couple synths, mostly cheap things, but recently I did a great find of a DX7 and a K2000S in rough shape for next to nothing.

The Kurzweil has a problem I can't troubleshoot by myself. I read manuals, boards, blogs, etc... with no luck.

The synth powers up, then works fine, though there is a huge background noise that I've been able to link directly to the effect engine. As soon as i set the dry/wet mix to 0%, the noise is gone.

Anyways, the thing is after a short delay (from 20 seconds to 5 minutes), tit will shutdown, or at least everything but the LCD screen. I've done a hard reset, I've opened the thing up and everything seems neat, the big a*s capacitors are visually ok. The power cord i use isn't the original but from what I understand it doesn't really matter.

I don't get why the synth would start up and work fine before shutting down. There seems to be ONE part that fails after a bit of time, and I clearly need help locating that part.

If you guys have any idea of things I could do to troubleshoot, that would be great. I paid 50$ for it and won't start spending unless I know it has a big chance of working. But I'm willing to open it again and use a solder if needed.

Cheers and thanks in advance :-)
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Re: Kurzweil K2000S shuts down

Postby madtheory » Sat Jan 12, 2019 12:26 pm

Given that the CPU is shutting down, the PSU needs checking because that could be fatal. Is it linear or switched? Then I would do the easy things: reset to factory, install firmware updates, remove all of the expansions (memory etc. if it has anything extra). Then I'd be using freeze spray on the relevant chips (sounds like the effects chip is going down first, then the CPU) to check for overheating, then measuring capacitors on their PSU line. I don't know if Kurzweil have a reputation for bad soldering on some units like Roland have had?
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Re: Kurzweil K2000S shuts down

Postby Tekhed66 » Sat Jan 12, 2019 1:49 pm

Does your K2000 have any expansion cards? ... I have a K2000 and had HUGE problems when I installed a non-genuine P/RAM card... the synth would boot up but switch off within less than a minute, show a corrupted display, freeze on patch changes etc etc... a real PITA

The synth worked perfectly without the card so if your synth may be playing up because it has a faulty card or some other faulty expansion card (btw - I replaced the non genuine card with a second hand genuine card and the synth worked perfectly).

Madtheory's suggestion to check the power supply sounds like a good first step.... the K2000 is getting on in age so there may be several things that are on the way out but as everything hangs off the PSU, I'd be checking that first.

Good luck with your repairs... the K2000 is a great synth
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Re: Kurzweil K2000S shuts down

Postby ALaMothe » Sat Jan 12, 2019 4:50 pm

Thank you for the complete replies. I will find a way to test the psu, and from what i understand i wont try to turn on the unit until i find the problem, because that could cause greater damage.

I dont think i have any add ons on the synth though at one point a technician opened it and installed the V3 and put a warranty sticker inside. I guess he maybe added some ram at the same time. I'll check it tonight. What should i look for to ID non genuine ram? Is there an easy way?
Thanks again!
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Re: Kurzweil K2000S shuts down

Postby ALaMothe » Sun Jan 13, 2019 2:43 am

So i've tested the ram by taking both pairs of simm cards out of the synth one after the other. In either situation, the synth would boot and work fine for a couple minutes, as before.

I also tested the voltages coming out the transformer and they seem fine (a bit higher but from what i understand thats ok) and perfectly stable.

So that rules out both the ram and the psu, am i right?
Now what should i do? Take the main board out to test every capacitor? Seems like a pita but ill do it if i have to.
Is there a way to disable the effect section completely? Since i know it is faulty because of the big hum, maybe its faulty enough to get the synth to shut down?

There is a small board fixed against the analog outputs of the machine thats called "fet protection network board k2000". I havent seen this thing on pictures of other k2000, does that ring a bell to anyone?

Thanks again for the support!
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Re: Kurzweil K2000S shuts down

Postby Yekuku » Sun Jan 13, 2019 11:34 am

ALaMothe wrote:Since i know it is faulty because of the big hum, maybe its faulty enough to get the synth to shut down?

A known issue for the k2000 is a faulty DSP chip causing noise issues , it could be whats causing the unit to shut off.
ALaMothe wrote:There is a small board fixed against the analog outputs of the machine thats called "fet protection network board k2000". I havent seen this thing on pictures of other k2000, does that ring a bell to anyone?

Another known issue is that the k2000 is killing the output FETS, this should be a modification added to prevent this.
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Re: Kurzweil K2000S shuts down

Postby ALaMothe » Sun Jan 13, 2019 2:57 pm

Breakout: it's a problem that can be solved by gently hitting the synth on the right side ahah... the effects stop going crazy and the k2000 stays on, meaning it's either a bad connection somewhere in the PSU or anything else physicaly weak. I'll just reopen it and turn it on and find out where exactly is the bug. Thanks for all the help. I noticed some weird acting on the effects part, so I might try to find a new DSP chip anyways.

BUT as you can imagine, there's more to this repair :-)

I can't access the MIDI section! And I mean at all. Nothing happens when I press the MIDI button. If a hold the program button and then press MIDI, the MIDI red light indicator turns on, wich means that the button isn't dead... it's something internal, probably software.

Once again, if anyone can help me troubleshoot this thing, go for it!

Thanks for the nice answers before, that helped a lot!
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Re: Kurzweil K2000S shuts down

Postby ALaMothe » Sun Jan 13, 2019 3:08 pm

Forgot to tell that I already did a diagnostic of the MIDI UART and it works (meaning it is a success if i have a MIDI cable running from in to out).
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