Kurzweil SP2X MARA (CPU) fail *update*

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Fnlorrain
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Kurzweil SP2X MARA (CPU) fail *update*

Post by Fnlorrain » Sat Apr 13, 2019 5:45 pm

Hello VSE readers,
I acquired an old Kurzweil SPX2 that plays, but has issues. It sometimes freezes, where the sound gets "stuck" and no buttons or sliders can stop it. It also can sometimes distort a clean piano program for a note or two randomly, or have pitch issues, where I play an octave but one of the notes is wrong. It will play the 3 demo songs mostly fine, but can also get "stuck" playing those, or play some random distortion. I performed a "reset", reseated every cable and replaced the internal battery then I ran the diagnostics, the ROM, RAM, SoundROM, DRAM and MIDI all pass, but the MARA (CPU) fails with some variation in the results. I also ran the panel scan, which indicated that the buttons knobs, slider, and wheels are all operating correctly, with the values in range. Main engine boards for this stage piano run a bit over $400, and I'm not sure I'm willing to spend that much on this old beast. I'm considering "reballing" or "re-flowing" the MARA (CPU) to the board, and was wondering if any of you have attempted to revive an old board this way. The chip isn't in a ZIF socket, it's just glued down, or simply soldered in place. I know that PC boards can be rescued this way, and am wondering if it is worth the risk to try it here.

For what it's worth, a few of the NAr test (MARA) results:
r.E.9 (g maybe?) CrN HE4 (incomplete 4 missing right top) CO dF Cd 62 FAL

r.E.9 (g maybe?) CrN HE4 (incomplete 4 missing right top) 83 d7 Cd 62 FAL

r.E.9 (g maybe?) CrN HE4 (incomplete 4 missing right top) 69 6F cd 62 FAL

any old Kurzi engineers out there? Thanks for any information or suggestions in advance.

**UPDATE** I did attempt a rescue on the main "engine" board of this 2007 stage piano. I filled the bottom of a loaf pan with a bunch of ratchet sockets to use as thermal mass for preheating the board. I heated it up to 350F, while it was heating in the oven I placed the board on some wine bottle corks on the back burner that serves as the vent for our range/oven to begin to preheat the board, and turned it over from time to time. You don't want to subject the board to uneven heat or rapid changes in temp (I learned from reading about DIY reflow attempts) I used a laser IR thermometer to check the temps during warm up and reflow. I pulled the pan from the oven and placed the corks on the sockets, then the board on the cork to begin working the heat gun. I tried to mask off the board with aluminum tape beforehand (the type used for ductwork) and aluminum foil to keep from heating other components (Particularly adding some physical pressure on the flat film capacitors on the bottom side of the board underneath the chip, to keep them from falling off while heating the CPU) and cut a hole in a piece of aluminum from a coke can that matched the size of the chip to use as a deflector. I used the laser IR thermometer while heating the chip with the heat gun, trying to maintain a 1 degree C per second ramp up until I got to 200C, it took some effort to prevent the temp from shooting up once there, pulling back the heat gun and closely monitoring the temp. At the highest I had measurements around 214. My setup failed a bit on one side, where I melted one socket for a wire connector, and popped one aluminum SMD capacitor, which I could have prevented by using the aluminum tape to form deflectors on all sides of the CPU, instead of counting on the coke can deflector, whose curve allowed too much hot air to heat other parts on the board. I won't know whether I fixed or bricked the board until I can procure the right capacitor and solder it in place. Fingers crossed, I'll update when I get that done. The important lesson I learned is to pay attention to masking, and to prevent heat from damaging adjacent components. Absent that error I'd be testing that keyboard right now.

Fnlorrain
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Re: Kurzweil SP2X MARA (CPU) fail *update*

Post by Fnlorrain » Mon Jul 08, 2019 4:13 am

**Update 2**
I did find the right capacitors that I had scorched but my BGA reflow did not work. I purchased a new mainboard for the piano and it works fine now. It's a dated instrument, but really feels and sounds great. If you ever run into one I can highly recommend it. Fantastic pianos and a very usable layout of controls, no diving through menus, everything is right there.

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meatballfulton
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Re: Kurzweil SP2X MARA (CPU) fail *update*

Post by meatballfulton » Mon Jul 08, 2019 2:21 pm

As a retired electrical engineer, after reading your update I was really impressed. I used to just bring my stuff into the lab at work where we had the proper tools to do that kind of repair.

BTW, I used to work with the guy who was lead engineer for Kurzweil's custom chip designs. I would have sold my wife and kids to have worked there back in their glory days.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

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