So about fixing an Arp Odyssey

[EricMc]

I found an Arp Odyssey for really cheap, the only problem is that evidently the oscillator 1 circuit doesn't work.

As far as repairs go I am not even sure where to start, it may just need cleaning , but if it is the oscillator itself how would one go about repairing it.

[schmidtc]

Difficult to say. The best way to repair something like this is to do everything you can think of to inspect the problem, and if you can't fix it, bring it to a technician. Download the service manual, check transistors, caps and the osc ic with a multimeter or scope. Not sure about finding a replacement VCO but ask Phil C. http://discretesynthesizers.com/arptronics/arp2800.htm Congrats on the find!

[EricMc]

Thank you so much for the step in the right direction.

I am going to get this thing to work by the time we track in January.

[hfinn]

I know I could get it working for you but I'm in Boston.

[Zamise]

I'd take mine apart and try reseating the boards first making sure no sodder points or pins are sticking up and touching something they shouldn't be, its not too dificult to take oddys apart, putting them back together may be another story, but still that would probably be the first thing I'd try doing. If it is the circuit, maybe you could pull that board out and find someone like mentioned already whos a good repair tech that could help, and if they know anything about old synths too would be good, and then send just that board to them. You don't necessarly have to send the whole synth I would think. There are 3 main boards in it. I don't remember which it'd be though, I just remember one board had an extra smaller filter board attached to it, and there is a 4th board that crosses all of them that connects them with long pins, thats the one I remember always having trouble getting seating right, having a pin or two not getting in the right hole because they bend pretty easily which caused some troubles on my Oddy. Not sure if it'd be the same thing but that cross board is one of the easiest things to check first once you open it up, it just pulls off and be carefull sliding it back on, that is if I remember right. There is some power junk on very back connected to the case tho where maybe something could be wrong too, might may be able to visually check them for leakage or burned out spots too, I'd say be extra carefull around those parts too if you decide to check in other ways like with an Ohm/Volt meter if knew what they are supposed to be measured at, I'd prob not put any fingers or limbs on those parts. Good luck, and remember to unplug from the wall first too. Oh and please don't hold me responsable for any further damage, injury, death or dismemeberment while you have it apart. Open at your own risk. Oh and, while its open it probably wouldn't hurt to make sure all the Jwires under the keybed are where they supposed to be and none bent or touching the bar thingy when not pressed, getting it back on try not to bend any either, its a bit tough, but doable.

Zam

[hfinn]

and if they know anything about old synths too would be good, and then send just that board to them. You don't necessarly have to send the whole synth I would think.

It would be way easier with the whole synth. I wouldn't want to try to find a way to power the board up, amplify it and test it, etc. Not to mention you would want to check the power supply and such. Think of it this way. If your car was broken would you take the engine out and send it to a mechanic?

[Zamise]

and if they know anything about old synths too would be good, and then send just that board to them. You don't necessarly have to send the whole synth I would think.

It would be way easier with the whole synth. I wouldn't want to try to find a way to power the board up, amplify it and test it, etc. Not to mention you would want to check the power supply and such. Think of it this way. If your car was broken would you take the engine out and send it to a mechanic?

Yeah true its easier, but its an option still I'd think, if possible do it and save a few bucks, install and test it yourself if you've got a screwdriver. I mean if I had to ship my whole Oddy out for just a board, I'd probably just ditch it or see if I can find another and salvage working parts off it. That just may be what I'd do tho, I tend to ship the smallest bad and rare parts out to see if they can match or rebuild them if I can deturmine what they are on my car/synth instead of sending the whole thing to Detroit or Cali for a rotted speed control assmbly on the carburator or ossilator on main board A. Just send the engine, carb or diaphram/circuit board, compasitor, or resistor out across the country, not the whole car/synth, thats what the local techs would prob do anyway and charge you 3 to 5Xs as much anyway.

I know Maschinengeist on here can prob use the businesss if your patient and like to support the VSEF community, sometimes I'd rather pay a little more for honesty and sincerity and good buisness practices, folks willing to take a shot in the a*s for the love of it. Find and ask Maschinengeist, he will help much more than I likely know for something like this on an Oddy.

Zam

[Steve Jones]

Which model Odyssey is it? The VCO would not be difficult to fix. If you have a 'scope I can talk you through it.

[hfinn]

Yeah true its easier, but its an option still I'd think, if possible do it and save a few bucks, install and test it yourself if you've got a screwdriver. I mean if I had to ship my whole Oddy out for just a board, I'd probably just ditch it or see if I can find another and salvage working parts off it. That just may be what I'd do tho, I tend to ship the smallest bad and rare parts out to see if they can match or rebuild them if I can deturmine what they are on my car/synth instead of sending the whole thing to Detroit or Cali for a rotted speed control assmbly on the carburator or ossilator on main board A. Just send the engine, carb or diaphram/circuit board, compasitor, or resistor out across the country, not the whole car/synth, thats what the local techs would prob do anyway and charge you 3 to 5Xs as much anyway.

But how am I supposed to tell what is wrong with it if all I have is the one part? Thats assuming you know that it is in fact that one resistor, transistor or chip. If you know enough to determine that and then remove the part and ship it out, why would you even need to ship anything? It sounds like you would know enough to fix it yourself. Also sometimes something will be wrong and the source of the problem will be something completely different. An Odyssey would hardly be too big and difficult to ship anyway. A CS-80 on the other hand....

[Steve Jones]

It is pointless shipping a board only unless the tech has an identical Odyssey to install the board into. For a start, VCO 2 of an odyssey will not run if there is not a keyboard plugged into the "A" board of the machine (the oscillators are on the "B" board). Without another machine, even if the tech connects the board to an external power supply, neither VCO will run, as no CV's will be present.

[Zamise]

They fix or replace the bad part on the board, ship it back to the owner to put back in and test. Doesn't seem like it would be that hard to me. Its just a suggestion if possible, if aint then it aint.

[Steve Jones]

They fix or replace the bad part on the board, ship it back to the owner to put back in and test. Doesn't seem like it would be that hard to me. Its just a suggestion if possible, if aint then it aint.

How would they know which part to replace if they cannot power it up and run it and diagnose the fault?

[Zamise]

That is a catch 22 question.

Again, its easier to be 100% sure it would work with the whole synth there yes I'd agree, the owner can do this too it doesn't have to be the repair tech., so its not absolutely necessary for the tech to have the whole synth. If the owner can get away with it, it might save a few bucks on shipping costs. Admittedly, its a big if, but how does the tech know a component meets specs and works or not before they even put it in the synth or on a board so they know it will power up properly? Think about that for a second. You guys are saying they replace each part one at a time then put it together, power it up and down each and every time until the thing decides to work for them? Assuming something on the new stuff hasn't gone bad too. Thats not what a good tech does in my mind, but it probably is a method techs good and bad use for diagnosing I'm sure probably more often then not I'd assume too. The owner could do this as well if they order all the parts, and then if you've got all the parts, what do you even need the old ones for, just use them all instead. I don't know how a good tech fixes just boards or a finds a small bad part on a board to fix, but I'm just thinking it might have been a possibility. Forget I even mentioned it.

[Steve Jones]

That is a catch 22 question.

Again, its easier to be 100% sure it would work with the whole synth there yes I'd agree, the owner can do this too it doesn't have to be the repair tech., so its not absolutely necessary for the tech to have the whole synth. If the owner can get away with it, it might save a few bucks on shipping costs. Admittedly, its a big if, but how does the tech know a component meets specs and works or not before they even put it in the synth or on a board so they know it will power up properly? Think about that for a second. You guys are saying they replace each part one at a time then put it together, power it up and down each and every time until the thing decides to work for them? Thats not what a good tech does in my mind, but it probably is a mehtod techs good and bad use for diagnosing I'm sure probably more often then not I'd assume too. The owner could do this as well if they order all the parts, and then if you've got all the parts, what do you even need the old ones for, just use them all instead. I don't know how a good tech fixes just boards, but I'm just thinking its a possibilitty. Forget I even mentioned it.

Why make guesses about what technicians do and do not do, and confuse people with uninformed advice?

FYI: A machine such as an Odyssey comes in with a dead oscillator. Here is what happens.

The tech checks the machine for electrical safety. Checks operation of all controls and listens for correct operation.
The tech then opens the machine, verifies correct operation of the power supply, looking for correct voltages and signs of supply ripple using an oscilliscope. These are the first things that any decent tech will do on any vintage machine.

Once it is determined that there is a dead VCO, the tech will use a scope and other test gear to determine why. Just because you cannot hear a VCO working does not mean that it is faulty. For example, if the VCO is not getting a control voltage, or if the voltage is wildly out, then it could be running at a frequency above or below the hearing range. I have seen this many times. So what then if Eric sends the VCO board to the tech, and the VCO is fine, and the fault is in fact on the A board or the interconnect board, and not on the VCO board at all?

If there is a fault in the VCO, is it in the summing circuit? The antilog amp? The VCO core/integrator? In the waveshape converter with it's old CMOS IC's? What if it is in the filter mixer circuit?

No, we do not guess and replace parts at random, we use test gear to find the failed component. To do that the board needs to be in circuit and powered up. And while we are at it we check and advise the customer if anything else is liable to cause a problem, in this case tantalum capacitors, which should always be replaced on sight in ARP's if they have not been done before.

The repair cost will likely be several times higher if he picks out a board and sends it to a tech to fix if the tech does not have anther identical machine to put the board into. He may not even send the correct board, as there are more than 1 board in an Odyssey that can stop a VCO working. I would suggest that no tech would do it unless they had another Odyssey to put the board into to run it in, and even then, they run the risk of the customer damaging the board when re-installing it by putting a power connector on back to front, and destroying a bunch of components, and then blaming the tech. Also, the board would not be calibrated to the machine, so the tuning and scaling will be out on both VCO's, and the second voice calibration will also be out.

So, I am sorry, but as someone who owns 2 Odysseys, and repairs or restores other Oddy's several times a year, I can tell you that there is no catch 22 about it. To quote a favorite saying....

"If you think it is expensive to get a pro to repair your vintage gear, wait until you see how much it will cost to get an amateur to do it". This also goes for taking advice on forums from people who are speaking from guesswork instead of experience.

Please find a GOOD tech near you and ship it to them, and you will get back a properly functioning, calibrated and checked machine, that is unless you want to play Fedex tag with PCB's and pay more and wait a long time to have a machine that doesn't work or sound it's best.

[Zamise]

Jesus! OK send the whole synth to them arleady so they'll quit crying about my stupid idea. I guess I'll go suck on my thumb to shut my retarded pie hole up now. I'm sorry for even mentioning it.