Anyone here got an OBXa?

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Anyone here got an OBXa?

Postby Thirteen » Mon Oct 20, 2008 9:53 pm

I have just wasted a whole lot of time building an OBXa from spare parts, and it is all working and calibrated, but I don't have a copy of the factory presets cassette to dump into it. There is a WAV floating around on the net but it is pretty useless as it doesn't have enough leader tone. Any of you guys got an audio copy of the factory cassette?
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Re: Anyone here got an OBXa?

Postby rachelp » Mon Oct 20, 2008 11:39 pm

Thirteen wrote:I have just wasted a whole lot of time building an OBXa from spare parts, and it is all working and calibrated, but I don't have a copy of the factory presets cassette to dump into it. There is a WAV floating around on the net but it is pretty useless as it doesn't have enough leader tone. Any of you guys got an audio copy of the factory cassette?


Wow - I wouldn't call that a waste of time! Could you load the WAV file into an audio editor and tack the leader tone onto itself and splice it digitally to make it
long enough? I did this with a sequence I made on the MC-202 that had a similar problem with the leader being snipped off when I transferred it from cassette.


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Re: Anyone here got an OBXa?

Postby Thirteen » Tue Oct 21, 2008 7:30 am

rachelp wrote:
Thirteen wrote:I have just wasted a whole lot of time building an OBXa from spare parts, and it is all working and calibrated, but I don't have a copy of the factory presets cassette to dump into it. There is a WAV floating around on the net but it is pretty useless as it doesn't have enough leader tone. Any of you guys got an audio copy of the factory cassette?


Wow - I wouldn't call that a waste of time! Could you load the WAV file into an audio editor and tack the leader tone onto itself and splice it digitally to make it
long enough? I did this with a sequence I made on the MC-202 that had a similar problem with the leader being snipped off when I transferred it from cassette.


rachel


Hi Rachel looks like that is my only option....
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Postby Thirteen » Tue Oct 21, 2008 9:48 am

Well, it turns out that there was also a faulty op-amp in the cassette circuit, so I have replaced it and have managed to get the first 4 banks in. What a job, basically a really nice case, with a keyboard and power supply and bender box in it and not much else. By the time I installed the upper and lower computer boards, upper and lower channel motherboards and 8 voice cards, found and repaired all of the faults in these boards and calibrated everything it was a big job, took me a couple of days, but I now have a really nice OBXa for my studio. I have enough bits to build another, but I think I will just keep them for spares and sell the case for someone who wants a better one if their machine is pretty rough.
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Postby rachelp » Tue Oct 21, 2008 8:00 pm

That's great that you can ressurect an OBXa. There can't be too many of those, fully restored
and operational. Do you have 8 voices in it and expanded memory? I would love some
sort of Oberheim synth. I have only played with an SX (preset) and that was a long time
ago but I remember I liked the big sound.


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Postby Thirteen » Tue Oct 21, 2008 8:02 pm

Yes, it's got the works. Fixing a really trashed Rev.2 Prophet 5 now, with a messy MIDI mod inside, makes the OBXa seem easy.
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Postby NYMo » Tue Oct 21, 2008 8:28 pm

Hi there,

I had 2 OBXa's and an OB8....I like blue synths especially ;-)

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Postby rachelp » Tue Oct 21, 2008 8:55 pm

NYMo wrote:Hi there,

I had 2 OBXa's and an OB8....I like blue synths especially ;-)

Cheers
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My Blue synth is a Polysix (blush)


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Postby Thirteen » Tue Oct 21, 2008 9:02 pm

This Rev.2 Prophet's giving me the blues....
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Postby NYMo » Wed Oct 22, 2008 8:51 am

Hi there,

My favourite blue synth....PPG 2.3 !

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Postby Thirteen » Wed Oct 22, 2008 4:06 pm

I feel like I should have a leather jacket with the sleeves pushed up and a mullet every time I play this thing. No matter what I do to the knobs it still sounds like "Jump".
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Postby NYMo » Wed Oct 22, 2008 5:05 pm

Hi there,

Seriously.... thats what I always felt about the OBXA.

Put that sound into unison, a judicious bit of filter, EG sustain full and that was my *balls* low end sound !
(and i DID have a mullett and my sleeves rolled up !)

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Postby rachelp » Wed Oct 22, 2008 6:23 pm

Ewww, mullets.

I do love those big slab keyboards though. There's nothing like it these days,
what with miniaturisation and Shenzen manufacturing. Everyone wants little
synths these days, like how mobile phones get smaller every year.

Even the Andromeda isn't a big slab keyboard. We need more synths
like the Prophet 5 and OBXa, JP8 and memorymoog - and heatsinks. Synths gotta have heatsinks ;)


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Postby BOB-SNARE » Thu Oct 23, 2008 11:45 am

Thirteen wrote:This Rev.2 Prophet's giving me the blues....


What's your opinion on replacing the regulators in P5Rev2 to switchers (powertrends PT5101 etc.)?
My rev. 2 needs some new J-wires.
Another rev. 2 I know of is also broken.
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Postby Thirteen » Thu Oct 23, 2008 12:59 pm

I have a spare parts Rev2 here, although I am putting a lot of them into the machine I am fixing currently. I haven't had experience with the tiny switching regulators so I can't really say, would RF noise be an issue? The only reason that this machine is so troublesome is because it is full of faults and is partly smashed, and has an old MIDI retrofit as well, so not really worth the effort, but the customer wants it fixed so I will get it going. Not much fun to fix, but they do sound good. I have a keyboard here from the old machine that I use for the occasional J wire.
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Postby Futureman » Thu Oct 23, 2008 1:32 pm

I'm sure I've seen 'J' wires for sale on ebay..

edit - Can't see any now.. ;[
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Postby no-fi » Thu Oct 23, 2008 2:25 pm

BOB-SNARE wrote:What's your opinion on replacing the regulators in P5Rev2 to switchers (powertrends PT5101 etc.)?
My rev. 2 needs some new J-wires.
Another rev. 2 I know of is also broken.


well, I know that the 5101 doesn't supply anywhere near enough current to the prophet's 5V rail. The others I put in seem to hold up the right voltage, but I can't test much with no 5V supply.....

Actually I'd really love to know the current requirements of the P5 rev 2 for the different supply rails.
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Postby BOB-SNARE » Thu Oct 23, 2008 3:01 pm

no-fi wrote:
BOB-SNARE wrote:What's your opinion on replacing the regulators in P5Rev2 to switchers (powertrends PT5101 etc.)?
My rev. 2 needs some new J-wires.
Another rev. 2 I know of is also broken.


well, I know that the 5101 doesn't supply anywhere near enough current to the prophet's 5V rail. The others I put in seem to hold up the right voltage, but I can't test much with no 5V supply.....

Actually I'd really love to know the current requirements of the P5 rev 2 for the different supply rails.


7805 TO-220 is 1A and so is the PT5101. Maybe your P5R2 has another problem which is drawing too much current...:) or crowbarring the 5V rail?
Or maybe with those extra memory mods and the cassette interface draw significantly more?
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Postby Thirteen » Thu Oct 23, 2008 3:25 pm

A modern 78x05 bolted to a heat sink should be able to deliver 1.5A. I don't think a switcher would last long at that current?
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Postby no-fi » Thu Oct 23, 2008 4:17 pm

BOB-SNARE wrote:7805 TO-220 is 1A and so is the PT5101.


naaaah... limiting factor with 7805 is junction temperature, which is a function of current draw and voltage drop and on time, and heatsinking, and of course, ambient temperature.... 1A is a suggestion. a bit like a speed sign on the road.
:)

there is no current hard-limit. And I'm sure you could pull HEEEEEEEAPS of startup current out of a TO-220 with no problems -- but maybe not from the PT5101.

Maybe your P5R2 has another problem which is drawing too much current...:) or crowbarring the 5V rail?
Or maybe with those extra memory mods and the cassette interface draw significantly more?


now I'm wondering if its the startup current? there's a lot of caps in there....


damn.
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Postby wez » Thu Oct 23, 2008 8:16 pm

Thirteen wrote:I feel like I should have a leather jacket with the sleeves pushed up and a mullet every time I play this thing.



Image
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Postby Thirteen » Thu Oct 23, 2008 9:26 pm

Ouch baby, VERY ouch!
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Postby NYMo » Fri Oct 24, 2008 8:19 am

Hi there,

Wez...... N.I.C.E ONE !

Ah...the Ultimate Support 3 tier....i first bought one in 81 and (believe it or not)
had a 73 Rhodes on the bottom tier, a Jupiter 8 on the mid tier and a Minimoog on the top !!!

That thing used to bounce like crazy when it was played....but I still had the best set up in town !! (Hobart)

Cheers
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Y
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O
[url=http://www.postimage.org/image.php?v=aV1ROzi9][img]http://www.postimage.org/aV1ROzi9.jpg[/img][/url]
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Postby wez » Fri Oct 24, 2008 9:29 am

oh yes how 80s was that stand!? shame it was 1992...

shortly after this pic was taken i spray painted it black... then replaced it with the big USS Stealth, now THAT was a serious keyboard stand.

ahh, those were the days... now if i could just find those old photos of me with the KX-5...
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Postby adamcal » Sun Oct 26, 2008 11:54 pm

hello, a bit late to this post, I have a fully working OBXa, and the original Patch cassette............................. Somewhere, next time im in the Junk room I will make a concerted effort to find it (the cassette I mean, thankfully I know where the synth is, I think)

I also have a nice A frame (junk room again) came with the PPG I got from kids in the kitchen (unfortunately dont have that anymore) sold the PPG to buy a jupiter 8, which I swapped for a ARP odyssey MK3 (woohoo, still have that one) I was always more of a Ultravox fan anyway.
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Postby Thirteen » Mon Oct 27, 2008 6:46 am

adamcal wrote:hello, a bit late to this post, I have a fully working OBXa, and the original Patch cassette............................. Somewhere, next time im in the Junk room I will make a concerted effort to find it (the cassette I mean, thankfully I know where the synth is, I think)

I also have a nice A frame (junk room again) came with the PPG I got from kids in the kitchen (unfortunately dont have that anymore) sold the PPG to buy a jupiter 8, which I swapped for a ARP odyssey MK3 (woohoo, still have that one) I was always more of a Ultravox fan anyway.


Thanks for that, it would be good to make a digital copy of your tape, when I repair dead OBXa's it's always good to be able to load some sounds into memory.

Re the A-frame stands, there were a few brands out the there at the time, some good, some awful. I remember the Ultimate ones has some sort of exotic material in the clamps, while the copies like the "world Tour" brand had plastic clamps. In all cases, people used to screw the clamps up too tight which resulted eventually in cracking. As I was a synth repair tech at Hutchings through the late 80's, I remember lots of customers coming through with smashed synths where the top rail of the stand suddenly spun round during a gig and dumped the top keyboards onto the ones below.
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