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preenfm2 and preenfm3 / Random patch resetting - was yellow oled issue

« on: June 22, 2019, 03:05:22 PM »

Greetings! I have a metal cased, R5C PreenFM2 complete with the wonderful Newhouse yellow OLED. I've had the synth for years and it's never worked right. However, what playing I've done has convinced me that this is - or could be - my all time favorite FM synth even with all the newer entries now on market. Alas, I get to working on it, resolve a problem or two, then life causes the work to be sidelined, repeat cycle, and here we are in 2019 and I still want a working Preen! When I first received and assembled the kit, there was a faulty trace that I fixed that was a manufacturing error on some of the r5c's. Shortly there after, I started getting display errors once the synth had been running for a while. Turns out the OLED was running really hot with way too much current draw. While the evidence indicated the OLED was defective from the gitgo, I purchased a replacement. Then the display errors returned, but this time the OLED was running cool and within spec. Flash forward to the present. I have performed the 22ohm resistor/shielding plate modification on the synth and now my display is rock solid and crystal clear...

HOWEVER, now when I run the synth, it will randomly unload/reset/reinitialize any loaded patches I have. For example, if I load a combo, a few seconds later it's changed to Preset 004, 005, and/or 006. Even that isn't stable as sometimes I'll watch a voice occasionally toggle from one value to the next (e.g. Back and forth between Preset 005 and 006). This seems to occur with the same random nature that the OLED display error occurred and has got me wondering if this has been going on the whole time I've had the new OLED, but went undetected because I was fixated on the display errors at the time.

Could this be noise on the USB_DP & USB_DN lines? Anybody else experience this? I'm VERY interested in 'eurofying' my Preen, but I need to get this synth up and running and rock solid first. It's been too long! 

TIA

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preenfm2 and preenfm3 / No buttons or encoders - solved

« on: February 09, 2016, 08:32:32 AM »

Hello Xavier,

I just built a PreenFM2 kit and had an issue I haven't seen on this forum before that I thought I would share.  When I first turned my preen on, I got the boot loader screen and none of the buttons or encoders would work.  After poking and prodding, I could get the synth to boot normally, but still with no encoders or buttons. A reboot would simply put me back to the boot loader screen.  After much more poking and prodding, I came to find that if I so much as lightly touched the leads around the resistor networks, I could boot into the normal screen.  Every subsequent reboot would take me to the boot loader screen until I lightly touched the leads anywhere around the control scanning circuits a which point I could reboot to the normal screen again.  I suspected a poor solder joint but could never locate one.  Eventually I got the schematic and systematically checked connections until I realized that pin 1 from both 74165s were not reaching pin 6 of the 405.  This turned out to be a defective trace on the pcb as opposed to anything I did or didn't do while assembling the circuit. A small wire soldered between pin 6 on the 405 and pin 1 on one of the 74165s was all it took to have my preen up and running! Now it's hooked up to an Undead Instruments Timefrog purring in the background while I write this email. Time to go play with it some more!