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elektro80
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Joined: Mar 25, 2003 Posts: 21959 Location: Norway
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Posted: Sat Nov 03, 2007 7:06 pm Post subject:
OSCar synth - schematics + service manual + prom? |
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Seems like I have an old OSCar synth incoming. The prom is supposedly dead and the whole thing needs some work. The synth has most likely been in storage for at least some 20 years.
Anyone? Tips, schematics and docs? Are there some out there who can shoot a prom with the right code for the OSCar? _________________ A Charity Pantomime in aid of Paranoid Schizophrenics descended into chaos yesterday when someone shouted, "He's behind you!"
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elektro80
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Joined: Mar 25, 2003 Posts: 21959 Location: Norway
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Posted: Sat Nov 03, 2007 7:23 pm Post subject:
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_________________ A Charity Pantomime in aid of Paranoid Schizophrenics descended into chaos yesterday when someone shouted, "He's behind you!"
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Nosferatu
Joined: Jul 27, 2007 Posts: 234 Location: Planet Rock.
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Posted: Sat Nov 03, 2007 8:00 pm Post subject:
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Ddepends on which version of the Oscar you have.
Supposedly dead! Well is it dead or not? It cant be half dead
If the board gets quite warm its not dead, reseat every chip in their sockets
to start with, check all clocks, its just Z80 the whole hoopla, very easy. |
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elektro80
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Joined: Mar 25, 2003 Posts: 21959 Location: Norway
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Posted: Sun Nov 04, 2007 6:28 am Post subject:
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I don´t have it yet. We´ll see. _________________ A Charity Pantomime in aid of Paranoid Schizophrenics descended into chaos yesterday when someone shouted, "He's behind you!"
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mono-poly
Joined: Jul 07, 2004 Posts: 937 Location: Rotterdam, Netherlands
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Posted: Sun Nov 04, 2007 8:49 am Post subject:
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The build quality of the oscar is very very poor.
Main problems are the bad connectors and sockets. |
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Peake
Joined: Jun 29, 2007 Posts: 1113 Location: Loss Angeles
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Posted: Sun Nov 04, 2007 3:13 pm Post subject:
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Check the AH archives at retrosynth.com. I'm pretty sure that it was there or Keyboard Mag US that a hint about easily fixing some OSCar problems came up. Let me rack my memory...Something about the battery or MIDI upgrade? I may be off on this one, but still send my regards for a great synth. Have fun! |
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Synthtech
Joined: Nov 23, 2007 Posts: 32 Location: Australia
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Posted: Fri Nov 23, 2007 9:36 am Post subject:
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Oscars weren't so well built, I used to do warranty repairs on them when they were new. Main issues are:
MIDI piggyback board sits too high above the mother board, making the top of the case bulge up on the RHS of the machine. This leads to cracking of the solder joints and tracks around the chip sockets connecting the 2 boards together. I usually replace the sockets and solder strips of new gold plated posts to the underside of the MIDI board at the correct length.
Interconnect pins between the pot board and the mother board corrode and crack.
Machine needs to be turned on each month to re-charge the battery. If the battery goes flat then much like a PPG the wavetables are lost and must be re-loaded, otherwise no amount of knob twiddling will give you a sound.
Tape loading of data is very level dependent, and the load procedure is not intuitive.
Useful trick: after re-assembling the unit with a good battery in place, the machine usually needs to be turned on and off several times to get it to boot OK, you can tell that it has properly booted because one (usually the center) of the row of LED's on the left of the machine will blink slowly.
I never saw a proper service manual for the Oscar, the only service data I ever had supplied to me was is a large sheet with a hand drawn schematic on it. |
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EdisonRex
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Joined: Mar 07, 2007 Posts: 4579 Location: London, UK
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Posted: Fri Nov 23, 2007 12:42 pm Post subject:
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hey, to the forums, Synthtech! _________________ Garret: It's so retro.
EGM: What does retro mean to you?
Parker: Like, old and outdated.
Home,My Studio,and another view |
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Synthtech
Joined: Nov 23, 2007 Posts: 32 Location: Australia
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Posted: Fri Nov 23, 2007 3:27 pm Post subject:
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EdisonRex wrote: | hey, to the forums, Synthtech! |
Thank you, I found the forum by chance, it has been very interesting to read some of the topics here. I mostly work only on vintage gear, I still see quite a few Oscars. Once the common problems are fixed they actually are pretty reliable as long as the batteries are changed every few years to prevent leaks. I had a Prophet 10 in this week and the battery had made a real mess of the processor board. |
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elektro80
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Joined: Mar 25, 2003 Posts: 21959 Location: Norway
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Posted: Fri Nov 23, 2007 4:41 pm Post subject:
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Hey, thx for the advice. Most excellent! [/i] _________________ A Charity Pantomime in aid of Paranoid Schizophrenics descended into chaos yesterday when someone shouted, "He's behind you!"
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Synthtech
Joined: Nov 23, 2007 Posts: 32 Location: Australia
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Posted: Fri Nov 23, 2007 5:32 pm Post subject:
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once you get the machine let me know and I will help out if you need it. _________________ Steve.
www.synthrepairs.com |
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elektro80
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Joined: Mar 25, 2003 Posts: 21959 Location: Norway
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Posted: Sat Nov 24, 2007 8:18 pm Post subject:
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I will! THX for the help so far! I think I´ll have it in next week or so. Right now I´m a bit rattled re an MCI JH-600. _________________ A Charity Pantomime in aid of Paranoid Schizophrenics descended into chaos yesterday when someone shouted, "He's behind you!"
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seraph
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Joined: Jun 21, 2003 Posts: 12398 Location: Firenze, Italy
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Posted: Sun Nov 25, 2007 12:44 am Post subject:
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elektro80 wrote: | I´m a bit rattled re an MCI JH-600. |
it could nicely sit next to the Petrof _________________ homepage - blog - forum - youtube
Quote: | Don't die with your music still in you - Wayne Dyer |
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Gothboy
Joined: Feb 21, 2006 Posts: 369 Location: Santa Monica, Ca.
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Posted: Sun Nov 25, 2007 7:17 am Post subject:
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mono-poly wrote: | The build quality of the oscar is very very poor.
Main problems are the bad connectors and sockets. |
That's why I have the ImpOscar! All the sound without the hassle.
Seriously though.....congrats on securing one even in it's present state. I don't know much about the repair but I'm sure we'll all knock out heads together and figure it out. _________________ Apple Mac Pro 3.1 2.88 GHz. Intel Xeon Quad
16 GB Ram
10.8.5/El Capitan
Novation SL49/Remote Zero
Mophox4, Nord Lead 2, Roland System 1, Novation Nova, Nord Micro modular, Korg Radias, Roland d-05, Yamaha A3000 sampler, Novation SL MK2 and Remote Zero controllers, Arturia Beatstep and SparkLE
"We are the music makers and we are the dreamers of dreams"
Dymaxion Vehicle Music at www.dymaxionvehicle.com/ |
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Synthtech
Joined: Nov 23, 2007 Posts: 32 Location: Australia
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Posted: Wed Nov 28, 2007 2:23 pm Post subject:
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I don't generally supply copies of schematics except to other service techs that I know well, but if you have problems with your OscAR I will be happy to direct you around the circuit until you find any faults. The OscAR schematics are too big for my scanner anyway. _________________ Steve.
www.synthrepairs.com |
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Regebro
Joined: Sep 12, 2004 Posts: 61
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Posted: Thu Mar 30, 2017 12:33 am Post subject:
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Quote: | Machine needs to be turned on each month to re-charge the battery. If the battery goes flat then much like a PPG the wavetables are lost and must be re-loaded, otherwise no amount of knob twiddling will give you a sound. |
I have one incoming soonish, and this has definitely happened (there may be more things wrong, the lights behave strangely).
How to I reload the wavetables? It seems I can dump them with sysex? Where can I find a sysex dump, in that case? |
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Regebro
Joined: Sep 12, 2004 Posts: 61
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Posted: Sat Apr 22, 2017 5:19 am Post subject:
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Found sysex dumps, will try, but the machine is not booting, at the minimum this is because of a bad battery. Will attempt repair but not this month. |
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Regebro
Joined: Sep 12, 2004 Posts: 61
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Regebro
Joined: Sep 12, 2004 Posts: 61
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Posted: Thu Jan 16, 2020 4:24 am Post subject:
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Would love to hear from other OSCar owners if they also have problems with ground loops.
Edit: From comments on my videos, the conclusion is that yes they do. "The OSCar ground hum" seems to be A Thing with OSCar owners. And that's because it doesn't isolate the 0V properly from the ground, in combination by having a terrible grounding design on the circuit board.
But I've fixed it now, by putting a small capacitor between the 0V and the ground. |
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Regebro
Joined: Sep 12, 2004 Posts: 61
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