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Just found this article: https://www.perfectcircuit.com/signal/oberheim-matrix-12 -geri

The following files have been uploaded to the Files area of the [email protected] group. * /Demos/The_Last_Emperor_tiny.mp4 ( /g/xpantastic/files/Demos/The_Last_Emperor_tiny.mp4 ) *By:* Xpantastic! *Description:* The Last Emperor by Mr Firechild. See the high-resolution video in YouTube at https://bit.ly/31OJdpt or more at http://firechild.se.

Dear all, I've got an xpander with a misbehaving voice number 6. When I switch the synth on voice 6 hangs and won't switch off. It's almost like the drone of vco2 but it's there even even when vco2 is not active. It's not on all patches particularly the stabby sort, but it is on all pads. Has anyone got any suggestions at what I might poke about at or what it might be? When voice 6 is off and I restart the synth it performs faultlessly. Many thanks in advance Shaun

I have a feeling I'm going to feel like a dummy for asking this, but does anyone know the meaning of the numbers on the front panel under the Single/Multi Patch Page Select section that are inside the diagram/flowchart circles? Example: VCO1 section shows Frequency with a number 1 inside a circle and VCA shows a 6 inside a circle. Second example: FM/LAG shows FM VCA with a number 1 inside a circle and LAG shows a 5 inside a circle. I've held off on asking thinking I'd find it in the owner's manual, but I haven't found it yet. Rob

Hi I am a new member to this list. I am looking for the "Matrix-12 Owner's manual Supplement" (scans or PDF) that the Matrix-12 Owner's manual (first edition) mentions on page 21. It is supposed to show all the 59 pages and sub-pages for programming the Matrix-12: a Matrix 12 pages directory... I would like to emulate the Xpander or Matrix-12 programmer for my Matrix-6. Thank you very much.

Hi all, I’d like to make a higher quality PDF of the Xpander Service Manual, to share with the group. The copy floating around the web is illegible in some places, and appears to have been scanned off a photocopy. (No slight to the hero that originally made it!) I hope to make much higher resolution scans, and perhaps correct some of the known errors. So, does anyone have an original Xpander Service Manual (US version) that they might sell? The ideal would be a well preserved version, with all of the original schematics. I’d also be happy to pay ‘rent’, and return the original to its owner when finished. Hopefully, someone out there has a nice original lying around?

I have an Oberheim Xpander (v 14. ROMS), which is failing all auto-tune tests. I have read every post related to tuning back to 2008 and have developed a game plan. I am posting here, please feel free to provide feedback. I am an electronic technician and I have access to the parts listed as well as a full set of test equipment. (Digital voltmeters, Oscilloscopes, I.C. Testers, etc) Please feel free to add comments or update me on what needs corrections. This is my game plan in repair of my Xpander. In my case I will test any I.C. listed before replacing. Oberheim Xpander Cheat Sheet Check output of each CEM 3374 VCO chip, pins 2,5,14,17 with oscilloscope. Any chip this missing any of the 4 outputs needs to be replaced. Reseat all IC’s as they are prone to “Chip Creep” over time. Retest unit before proceeding. Check underside of voice board for bad solder joints, repair as necessary. Replace C233, C333, C433, C533, C633, C733 & C237, C337, C437, C537, C637, C737 & C249, C349, C449, C549, C649, C747, C749 they are all 2.2uF 50v C103, C104 15uF 35v Check operation of: U811 DAC U816, U805 Multiplexer CD4051BE U812, U815, U813 Op Amps TL081, TL084, TL081 U814 Analog Switch CD4053BE The CD4051BE & CD4053BE are known to die over time. U706, U707 Voice 1 U606, U607 Voice 2 U506, U507 Voice 3 U406, U407 Voice 4 U306, U307 Voice 5 U206, U207 Voice 6 U805, These are all CD4051BE 8-Channel Analog Multiplexer/Demultiplexer, These are known to fail over time. U805 is responsible for collating the temperature compensation voltage from each CEM. U814 can also fail, CD4053BE, U814 is responsible for combining a stream of high and low resolution CVs for delivery back to the analog world. Kinda crazy, but this whole rig is running constantly. e.g. The tempco CV is updating constantly; You can hold a cold finger to one of the voice’s CEMs and see the DAC output change in real time. Any parameter changes that affect CV are also updated through here in real time U108 (LM311N) is a comparator that essentially takes the audio from the voices, and turns them into square waves for delivery back to the U9xx block for tuning. It's always running, outputting a square wave version of anything the voices put out. Check output with scope. Once U108 has turned everything into pulses/square waves, there isn’t a need for ADC, so it’s signal is fed directly to U915, U916 and U921. By my estimation, U915 is used exclusively for tuning PW1&2. (On a side note, the square waves from the Xpander’s VCO are their own little bag of tricks. It’s not generated by the CEM VCO ICs directly, but derived in realtime from a combo of the SAW waves and CV for pulse width, spliced together per-voice by a CMOS/OP-amp combo. Lots of analog synths do something similar.) U916 works in tandem with U921 to address memory, possibly responsible for storing the newly derived tuning offsets.

Hi, My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas? Thanks in advance, David

Hello; I've subscribed to this wonderful group because I recently got an Xpander that exhibits some weird tuning problems. It's a "Made in U.S.A." model running firmware 1.0. When I start it I can sometimes directly afterwards tune all 6 VCO's without a problem once (!); however any subsequent tuning attempts result in FAIL for all 6 voices. After it warms up for some time the VCO's are starting to come around until all 6 VCO's tune again. It's not reliable, though - subsequent tunings might again disable (and later re-enable) voices. PW practically never tunes ok; occasionally I can get one or two voices to not FAIL. RES and VCF always (!) tune fine. When I enable the voices they often sound fine although with a slightly different timbre (I believe that's the missing correction offsets for the PW). Sometimes one or two oscillators are out of tune in a certain range - as if the offset for that range is missing. I've recapped the power supply (there was some ripple) and also the voiceboard. The machine originally had one dead 3372 and 3374 each; I've replaced them (though the 3372 is a "D" revision). Voltages are ok. I've also found at least two dead 4051; and to be on the safe side I've swapped Ux06 and Ux07 for all voices. Right now I'm poking a bit in the dark. The behaviour seems to hint at a thermal problem; however I don't quite understand why the VCO's tune eventually but the PW mostly doesn't. All voices definitely "make it" to the output of U108 and look pretty normal there during the tuning routine. A working hypothesis of mine at the moment is that the zero crossing detection doesn't work as it should. All measurements for VCO and PW are done with rectangular waves while the RES/VCF measurements are done with sine waves. Perhaps some slew rate problem? Sadly that part of the voice board circuit isn't (in my opinion) really well documented (page 51 of the service manual). Right now I'm thinking of swapping most of the U900 group chips. I'd be very happy about any further ideas, suggestions and pointers. -- Malte Rogacki <gacki@...>

Just a quick note about a successful Xpander repair: My Xpander was suddenly failing all tuning tests. Consistently at power up, all VCOs and VCFs ramped up in pitch until they were ~4 octaves too high, then stayed there. Fixed by replacing IC U814. Some details for future generations, and a confession: I actually caused this problem myself when using canned air to dust off the processor board while doing some scope work. Held the can in just the right (wrong) way to invoke the ice breath powers of difluoroethane, which is about -50°C. It foamed all over the upper section of the DAC/tuning ICs, (U801 through U806). Then I realized I had left the power on… (insert eye-roll emoji here.) After the stuff eventually evaporated, (technically it boils at room temperature), I found the symptoms described above. Holding down a chord at power up sounded like the THX “deep note”; pitch on all voices rose ~4 octaves, then stayed there. I was able to trace the problem backwards from the DAC output. The scope showed VCO1&2’s pitch CV and VCF’s were affected, but PW, level and VCA were still stable. This pointed to U814, which is responsible for assembling the final DAC output by switching between the high and low resolution CV signals on their way to the CEMs. (Pitch for VCOs and the VCFs frequency get the high res version, PW, level and VCA get the low res.) Oddly, U814 was not in the line of fire, but even the service manual reminds that that IC is extremely sensitive to shorts (it’s a CMOS), so it must have temporarily suffered a voltage spike, or perhaps a static shock from the blast, as the other components temporarily froze. I replaced U814 and all was good. It’s a CMOS analog multiplexer switch, part # CD4053B, $0.51 at Mouser. I also replaced all of the ICs that were hit, and all the rest in the U800 section, just as a precaution. Total cost was probably less than 5 bucks. (Freezing ICs is actually a common technique to isolate problems in circuitry, so those in the line of fire were probably fine, but I figured why not.) The THX effect was probably caused by a nearby capacitor soaking up voltage unchallenged by the failed multiplexer. Anyway, just had to share with someone. Hopefully someone might find this useful in the future. And if you’re wondering, the canned air and I are no longer on speaking terms.

Hi all, Im looking for suggestions on how to fix the sticking buttons on my Xpander. When pressed down, they stay down, and can only be brought back up by scratching at their sides, or, gasp, tugging at the side with a sharp object. It seems like they are slightly offset, rubbing against the front panel. The only option I can think of is to open her up, and bend the buttons where they sit on the PCB to get them up striaght. But I've never seen the inside of an Xpander, so I don't know what to expect. Anyone seen this before? Any ideas for a cure? Any advice appreciated.

Wanted ! Matrix 12 US version EPROM dumps or chips. Please if somebody has original US version bins, contact me. Can't believe that nobody has it. This synth is/was very popular and has been serviced a lot. Best regards...

Has anyone here attempted to disassemble the XPander or Matrix 12 ROMS? If so, where is the dissembled source code at? If not, what would you recommend using getting the ROM bin files that are separated into even & odd addresses, into 1 contiguous file? I don't want to goof that up and make the job more difficult. Thanks Tony

Hello. My question is regarding Matrix 12 RAM chips. On CPU board there are RAM0, RAM1, RAM2, RAM3 chips. Usually they are 6116 (2x8) in every Matrix 12 guts that I've seen. (Xpander states 3 x 6264.) In Matrix 12 service manual there's a note that 4 x 6264 can be used instead of 6116. What's the advantage of this ? Is it really can quadruple RAM capacity ? In this case probably all other chips are not needed. Matrix has 16 RAM ICs, if using 6116 it turns out 16x2x8 = 256. And if using 6264 ---- 4x8x8 = the same 256. But as I understood, even in case when using 4 x 6264s, all other ICs (except U24 and U25) are also needed. Can somebody put some light on this theme. Thanks...

Hi everyone! Unfortunately I’m writing here because my Xpander has some problem. Every test on voice 6 fails. VCO, PW, RES, VCF and VCA. So I suppose it’s not a CEM problem because it would fail only 1-2 test, or a power supply problem, because in this case it would affect all the voices. I’ve swapped some IC, but the problems remain on the same voice. Please could you tell me and confirm me the the first one on the left is the voice 6 and the last one on the right the voice 1? Thank you very much, Stefano

Hello, The Xpantastic! Yahoo Group will be transferred to Groups.io. Members, archives (without attachments, however), photos, files, links and databases will be transferred. It will take about a week and you'll be notified. Thanks Jacob et al.! Tiitu

I'd hate to see all of us lose touch due to Yahoo killing all of the Yahoo groups. Does anyone have any ideas on how to keep this group alive- elsewhere? Thanks Tony

Someone on the AH list is asking about how to remove the matte finish from an Xpander and while I found some photos I can't seem to find the info on how to do it. I vaguely remember that it's not all that difficult but I can't find any instructions. Anyone know where it is? Gloss finish Matrix 12, for reference: https://www.matrixsynth.com/2016/09/vintage-analog-oberheim-matrix-12-with.html Thanks, Seth

Please, here are some Oberheim Xpander tracks from SoundCloud: https://soundcloud.com/nycsynth/stay-with-me https://soundcloud.com/stephen-richard-williams/xpander-bliss https://soundcloud.com/zapgalaxy/jan-2014-studio440 https://soundcloud.com/paolo-dollorenzo/acidfromscratch-part-4 https://soundcloud.com/c1t1zen/end-credits https://soundcloud.com/noiseprofessor/xpander-demo https://soundcloud.com/jnln/regalish https://soundcloud.com/wheatfield-1/power https://soundcloud.com/fluxusanais/the-universe-in-a-nutshell https://soundcloud.com/modularsamples-com/little-chord-4 https://soundcloud.com/modularsamples-com/simple-mod-saw https://soundcloud.com/uvi-official/synth-anthology-ii-san-juniperan-by-torley Tiitu

Hello there! I just bought a Xpander but the voices are all messy .. the tune test fails on every voices and there is no bass sound. The notes are the same below C3... vcf is OK but I don't know how to test the DAC..?