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Oberheim OB-1 Dead Oscillator Repair - Synthchaser

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We have a little peek inside the Oberheim OB-1, the 1 voice/monophonic predecessor of the mighty OB-X, and track down the problem causing one of its oscillators to be silent.
Parts for DIY repair and restoration of Oberheims are available at my website. I also repair and restore Oberheims and other vintage synths for customers around the world.

Опубликовано:

29 авг 2024

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Комментарии : 35

@noglobalists 3 года назад

I was product specialist/tweaker/final tester for Oberheim when they brought this out. I remember the first run of these OB-1's (the name inspired by Star Wars) being a nightmare; the majority failed. All kinds of weird problems. It might have been the Harris chips. We had a lot of trouble with those in the 4- and 8- voice programmers. Normally, those tempco resistors should be positioned directly over the 3086 xsistor array, btw. I think I may have been responsible for the original factory patches in the OB-1. I know I worked up a bunch for that or its immediate successor.

@Doctormix 4 года назад

niiiiice!

@AlexBallMusic 4 года назад

These are so satisfying.

@AlainHubert 4 года назад

Great stuff ! Thanks for sharing! I didn't think that there would be this many components in a relatively "simple" monophonic Oberheim.

@mschorer 4 года назад

Nice synth, great repair. Bring on some more OB1 videos please!

@AdamTheAd-vanc3d 4 года назад

Super super insightful Its intresting to see what makes these instruments buzz. For some reason I had it in my head that this synth uses the cem 3340s for oscillators. Also intresting to see the method used for coupling the tempos to the transistor array for the expo converter part. Maybe give us a circuit board tour vid, that would be good to see .

@madFame 4 года назад

Second that Adamski! Great work Synth Chaser I wish you lived next door to me, my Juno has been giving me grief for years :( Adamski, your DIY synth project is epic, well done man.

@F0nkyNinja 2 года назад

You might be confusing it with the Pro One, the Prophet 5 monosynth. This actually came out in '78 before the discrete Oberheim OB-X and years before '81 Pro One.

@AdamTheAd-vanc3d 2 года назад

@@F0nkyNinja On further look on the schematic it looks like your right . Discrete VCOs both 👊🏾👊🏾👍🏾👍🏾

@janne-seta 4 года назад

Great stuff!

@jeffreyhyde501 4 года назад

I say make another video of this, but the fully restorative version, including maybe a comparison of this with the OBX Voice cards too, besides I await the day we see a Full Restoration of an OBX, thus would perfect.

@Synthchaser 4 года назад

Will try to make another video of my OB-1. OB-X's don't come through often, but next one that does I'll try to make another OB-X video as well.

@RegebroRepairs 4 года назад

This is super educational, even though I don't have an OB-1. The only analogs I have is the OSCar and a Deepmind, but it's still very helpful to see how you look for problems in general.

@noglobalists 3 года назад

The OSCar is a fun little keyboard. I met the developers, representing them through Europa Technologies (circa 1982-3), who also represented PPG, those somewhat perplexing German keyboards. I was the product specialist for Europa. Oberheim, too, some years before. It was sales guys from Oberheim that formed Europa; my old buddies!

@zorgitron 4 года назад

Excellent well made video! Gave me some ideas for fixing my dead VCO SH2000.

@ScottFromCanada 4 года назад

Great video. I've never seen inside one of these. Actually, I've never even seen one in person!

@Dolores5000 3 года назад

Fantastic

@annother3350 2 года назад

Help the OB-1 -- your my only hope

@synthead 4 года назад

Wow, great footage of the inside! The PCB looks super identical to the OB-X! These circuits are suuuuper finicky. I dropped a small metal screwdriver onto an OB-X voice board while tuning it and killed an oscillator. I happened to toast a transistor somehow, so I replaced it, then accidentally put the board in while the synth was on and cooked it again! I traced the issue back to another transistor and eventually got everything 100% again, but wowee, I have never seen a synth so happy to make stuff pop. If you're making another video, could you do a rundown of the DAC, ADC, and computer for the patch memory? I imagine it's almost exactly like the FVS-1, but I'm curious! If you have an OB-X voice card handy, it would be interesting to see how they compare, too!

@carlosmedrano7005 4 года назад

I hope you don't mind me asking a n00b question from a long time follower. I decided to purchase an oscilloscope because I want to take my troubleshooting to the next level. Is it a good habit to connect your probes ground to the chassis (or a circuit boards ground) you are working on? I thought I've seen you use your oscilloscope in the past but never got a good camera angle to see if you do this EVERY TIME or not. This video shows that you do. Do you also connect it to the chassis or ground if your trying to see a sawtooth or sine wave?

@Synthchaser 4 года назад

You've got a sharp eye. I don't usually ground my probe to the chassis, I usually take advantage of the fact that my scope and the synth are plugged into the same circuit, and that they are both share a common ground (earth, through the 3rd pin of the power cord). In some cases like this, the synth doesn't have a 3 prong cord, in which case, I'd need to connect the probe's ground to the circuit ground. On the OB-1, the ground of the circuit is connected to the chassis, so I can just clip onto the chassis. In other cases, the circuit ground isn't connected to the chassis, and then I'll need to connect the probe to a point on the circuit board. In yet other cases, the synth may share a common ground to the scope, but the signal I'm looking at is very small, so I'll want to connect the probe's ground on the circuit board I'm probing at the closest ground to the signal I'm measuring, so I can view it with the least amount of noise. Not the straightforward answer you were looking for, I bet!

@carlosmedrano7005 4 года назад

@@Synthchaser this helps! thank you!

@synthland4526 4 года назад

You are the best!!!! I have a question. When i turn the frequency modulation pot on my OB 8 it scratches the frequency modulations sound. Next question is how hard is it to replace cmi fairlight screen and an ppg waveterm screen? Cheers i love you.

@wirenutz7869 2 года назад

OB one Knobi !

@synthdude7664 3 года назад

Hey, by any chance do you know if the obxa has way lower output than all other synths? My obxa sounds great, but the output has to be maxed to even be 1/3 of the volume of every other synth I have Thanks, Nick