Scored a Juno-60

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Re: Scored a Juno-60

Post by synthparts » Sun Oct 09, 2011 12:54 pm

Projectile wrote: In other news, my Juno-60 is still tanked. I've put about 50 hours of work into it and still can't get it up and running properly (and I'm someone who has a clue what I'm doing). I have a few things I'm going to try before I give up and start asking for help on the internet. It seems the Digital logic board is pretty messed up. At this point it's looking like the CPU might be the culprit, but it's killing me becasue it's the most expensive chip on the synthesizer and the last thing I would expect to go bad. I need to get access to a scope so I can actually see what's going on. This has been a frustrating experience to say the least.
Actually the IR3R01 EG chips are the most expensive chips in there. I have a working Juno-60 CPU if you need one.
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Re: Scored a Juno-60

Post by factorplayer » Mon Oct 10, 2011 4:54 am

Projectile wrote:
In other news, my Juno-60 is still tanked. I've put about 50 hours of work into it and still can't get it up and running properly (and I'm someone who has a clue what I'm doing). I have a few things I'm going to try before I give up and start asking for help on the internet. It seems the Digital logic board is pretty messed up. At this point it's looking like the CPU might be the culprit, but it's killing me becasue it's the most expensive chip on the synthesizer and the last thing I would expect to go bad. I need to get access to a scope so I can actually see what's going on. This has been a frustrating experience to say the least.
Thanks for the info Proj and sorry you are having such a hard time with your Juno. Is the current issue something that just came up out of the blue?

I am feeling pretty lucky with this score and fortunate that it has no major issues. I just did some recording with it this weekend on a friend's album. I'd like to take it to a gig or two, but I'm wondering if that's not such a great idea. I'm thinking I should just baby it at home maybe.

That leads into another general question - What best practices do you guys suggest for maintaining a synth like this or just in general?

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Re: Scored a Juno-60

Post by Projectile » Sat Oct 15, 2011 10:38 pm

synthparts wrote: Actually the IR3R01 EG chips are the most expensive chips in there. I have a working Juno-60 CPU if you need one.
Wow, that's nuts. I'm glad mine doesn't have any voice problems.

Thanks for the offer on the cpu, but at this point I figure if the cpu is bad I'll just install a minerva kit. The only reason I haven't bought a minerva kit yet is because I would feel really stupid if I spent all of that money on a minerva kit just to find out that it doesn't fix the problem. I want to make sure I exhaust all other possibilities first.


factorplayer wrote: Thanks for the info Proj and sorry you are having such a hard time with your Juno. Is the current issue something that just came up out of the blue?
...
That leads into another general question - What best practices do you guys suggest for maintaining a synth like this or just in general?
The Juno was like this when I got it. It hasn't worked in years. Luckily I scored it for free, so I can't really complain. Though, I didn't expect to have to put nearly this much work into it.

The one thing that ALWAYS will be an issue on any gear as old as the juno60 are the electrolytic capacitors. The gear might still work okay, but the electrolytic capacitors are usually way out of spec after that many years and they will eventually fail. It's guaranteed. The electrolytic caps from the 80s were really only made to last about 10 years. Newer caps are better, but they still have a limited lifespan.

It's a good idea to at least replace the power supply caps every 15 years or so. They get a lot of abuse. The rest of the electrolytic caps can probably wait a little longer, but if you want your synth to be in tip top condition, I'd replace them too. In my experience, it noticeably tightens up the sound. Though, a lot of techs are in disagreement about this. Some say don't bother replacing the (non-power supply) caps unless they are a problem. Others say it should be mandatory. Just beware that there are like 90-something electrolytic caps in the Juno60. Replacing them all is a big job. It took me a whole weekend, and 30 bucks in parts to do mine.

(Note, that everything I said about electrolytic capacitors is also true of tantalum, but the Juno60 doesn't have any tantalum capacitors so I left that part out. If you have a synth that has tantalum capacitors, and it is giving you trouble, always suspect the tantalum capacitors first. Just go ahead and replace them. Tantalum caps are notoriously prone to failure.)

Other than that, just clean the pots when they get scratchy, keep the synth out of the sun and humidity, and address any problems as the crop up. The Juno60 is built like a tank and should last for many more years.

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Re: Scored a Juno-60

Post by madtheory » Sat Oct 15, 2011 11:20 pm

The old adage-if it's not broken, don't fix it- applies to caps too. It's so easy to diagnose a bad cap! And what do you mean "out of spec"? Tolerance on a cap is often around +/- 30%! And there are caps from the seventies onwards that are specified to last 35 years. Read a data sheet, it's educational. I'm sorry, but the fact that your Juno is still non functional proves that re capping is an Internet myth.
Do you have the service manual and a 'scope? That's how one diagnoses these things.

EDIT: just read you don't have a 'scope. A used Hitachi 15MHz dual trace is cheap bullet proof and all you need for this kind of work.

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Re: Scored a Juno-60

Post by Nannerfan » Sun Oct 16, 2011 2:07 am

Diametro wrote:To Ju-60's credit, though ... lots of overlap in their sonic signatures ... Without a doubt, Ju-60 is the synth closest to JP8 sound ...
Call me crazy, but I think the Akai AX-80 is the closest thing to a poor man's Jupiter 8

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Re: Scored a Juno-60

Post by Alex E » Sun Oct 16, 2011 8:04 am

Don't mean to stray off topic here, but the Jupiter 6 was literally supposed to be the poor man's Jupiter 8 when it came out. ;)
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Re: Scored a Juno-60

Post by Projectile » Mon Oct 17, 2011 8:33 am

madtheory wrote:The old adage-if it's not broken, don't fix it- applies to caps too. It's so easy to diagnose a bad cap! And what do you mean "out of spec"? Tolerance on a cap is often around +/- 30%! And there are caps from the seventies onwards that are specified to last 35 years. Read a data sheet, it's educational.
Didn't I just say there is a lot of disagreement on this issue? Did you miss that, or what? I think I tried to paint the issue as objectively as possible and give both points of view. I know there are people out there who would rather stick to the old adage of "it's not broken, don't fix it." What I can't understand is why you insist on having such a patronizing, dickhead attitude about it. You are welcome to your opinion, but don't act like your opinion is the only valid one. Spewing a bunch of absolute nonsense doesn't help your case either.
madtheory wrote:Read a data sheet, it's educational.
First of all, I know how to read a f**k data sheet. Since you too can read a data sheet, then you should also know that there are a lot more specifications to a capacitor than just the capacitance: leakage current, ESR, ESL, temperature dependance, noise, dielectric absorption among others.

When an electrolytic capacitor ages, the electrolyte literally evaporates. As the electrolyte dries up, there is more leakage current, and in turn, more heat, which accelerates the process. It is not a question of 'if' an electrolytic capacitor will fail but 'when' it will fail. And when they fail, they can fail catastrophically, exploding, leaking corrosive electrolyte onto other components, cause short circuits, etc. Even if the cap hasn't failed, that doesn't mean that it's working properly in the circuit. Especially in high-speed digital circuits, often the capacitance rating isn't the only spec that matters.
madtheory wrote:there are caps from the seventies onwards that are specified to last 35 years.
There were never electrolytic capacitors made in the 70s that were specified to last 35 years. That's absolute nonsense. The life of an electrolytic capacitor is dependent on many factors and a manufacturer will almost never try to predict it in terms of years. If specified at all, it is usually listed as hours under certain operating and storage conditions. This is impractical for most devices, which are not used daily and stored in variable conditions, so the general rule of thumb is that if an electrolytic cap is more than 15 years old, it's probably due for replacement. Realistically speaking, many capacitors in audio circuits (where they are used lightly and stored in moderate temperatures) can last quite a bit longer, which is why gear 25 years old can still function properly. However, this is not true of power supply caps. Power supply caps receive a lot of abuse and are almost always out of spec in any gear more than 15 years old. In my expereince this is almost universally true.

Personally, I've done total re-cap jobs on more than half-dozen old amplifiers. Usually, these amplifiers were still functioning properly, but long overdue for a recap. The sonic difference in replacing the electrolytic caps in these amplifiers was usually quite remarkable. I'm not talking a subtle improvement in fidelity. I mean in some cases the amp would have double the gain than before the recap. In other cases it would sound like a completely different amplifier altogether. It's that dramatic.
madtheory wrote:It's so easy to diagnose a bad cap!
It's easy to tell if the cap has completely failed, but it's not so easy to tell if the cap is out of spec. The only way to properly test a capacitor is to completely remove it from the circuit. You cannot properly test a capacitor without desoldering it. If I'm going to take the time to desolder a cap, why on earth would I put it back in the circuit if it is already overdue for replacement? Electroyic capacitors only cost a few cents to a few dollars for larger values. If you are already taking it out of the circuit, you might as well replace it with a new one.
madtheory wrote:I'm sorry, but the fact that your Juno is still non functional proves that re capping is an Internet myth.
What kind of moronic, crack smoking logic is that? That doesn't 'prove' anything of the sort. I didn't recap my Juno becasue I was sure it would fix the problem. I had planned to recap it from the start. Since I was going to do it anyway, I figured I might as well do it first so that I could eliminate any electrolytic capacitor related issues from the list of possible sources of the problem. It's true that I hoped it would fix the problem, but I wasn't surprised when it didn't, and I would still recap it again regardless.

Apart from damaged power cords, failed and failing electrolytic capacitors are the number one source of problems in vintage audio equipment. That is a fact. Whether or not you think that warrants replacing them before total failure is another issue altogether. But you can't 'pretend' that this is a black and white issue. Many pieces of vintage gear will benefit greatly from a recap. This has been my experience time and time again.

Some of us want our gear to perform as best as it possibly can, and some of us also believe in preventative maintenance. That means replacing electrolytic capacitors.

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Re: Scored a Juno-60

Post by madtheory » Mon Oct 17, 2011 6:41 pm

Your insult laden reaction speaks volumes: you can't present a reasoned argument because you don't have one. And despite your claim you did not present a balanced viewpoint- so I posted to redress the balance, and give you some advice. Y'know you're really groping in the dark with this stuff if you don't have an oscilloscope?

I'll address a few points from your rather scattered rant, as best as I can:

I never said DON'T replace caps. I said REPLACE THE ONES THAT ARE BROKEN. That's implied in the old adage. It's not a matter of "belief"- this is electronics, not religion. By the way "broken" means "out of spec".

Philips are just one manufacturer who made electrolytics for use in passive crossovers, spec is c.35 years. That's enough info for you to Google the data sheet. Granted they're expensive, but it throws your generalisation into disrepute. I've had plenty of gear from the seventies where the PSU caps were functioning perfectly. It's an easy thing to test anyway- if you've a 'scope. So you can't make that claim because you can't test the thing properly.

You obviously haven't seen a lot of failed electrolytics- more often than not, they don't fail spectacularly. Usually you'll see a leg askew, or some of the electrolyte building up around the leg/ body interface as it leaks. If that happens underneath the cap it can be hard to spot. Takes practice to locate them, but it's a h**l of a lot more efficient than replacing every single one. You have time left over for life and stuff like that.

Tell me, did you just replace the spectacular failures in your Juno? I guess not. So how do you know they were broken? You didn't. So is recapping willy nilly some kind of therapy? Because it has no value for repair.

Maybe you have improved the amplifiers you re capped, but where's your proof? Such major improvements should show up easily with a simple bandwidth test, for example. Did you actually test the amp as you replaced each cap, just to make sure that was exactly what was creating the alleged improvement? DId you try the normal approach with another amp- replace only broken caps- and compare the results? Maybe it's a case of sunken bias? That's a tough one to own up to.

There might be variations when you change the caps, but that's because the error margin is so wide with caps. Any half decent design allows for that error. So when you say "out of spec" it doesn't make sense. We're talking +/- 30% here for goodness sake!

Ya, caps are cheap, but replacing 30 of them is time expensive. How cheap is your time?

Yes, clearly capacitance is not the only parameter of a capacitor. But in most audio and related circuits, it's the only parameter that matters. If a cap is "out of spec", the evidence is in the performance of the circuit elements nearby. That is determined by the parameters given in the service manual, and the level of one's diagnostic skills. But given the lack of logic in your post, I guess maybe you're not too hot on diagnostics? PS I made that point clear so you will know I'm not patronizing.
Projectile wrote:...so the general rule of thumb is that if an electrolytic cap is more than 15 years old, it's probably due for replacement.
You appear to have contradicted your entire stance... and it's the only sensible point you've made.

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Re: Scored a Juno-60

Post by Projectile » Tue Oct 18, 2011 1:23 am

madtheory wrote: I never said DON'T replace caps. I said REPLACE THE ONES THAT ARE BROKEN. That's implied in the old adage. It's not a matter of "belief"- this is electronics, not religion. By the way "broken" means "out of spec".
There is no way to test a cap to ensure it meets specification without first removing it from the circuit. how many times do I have to repeat that?
madtheory wrote:Philips are just one manufacturer who made electrolytics for use in passive crossovers, spec is c.35 years.
Prove it. Where is this mythical data sheet you speak of? I did a Google search and didn't come up with squat.
madtheory wrote:You obviously haven't seen a lot of failed electrolytics- more often than not, they don't fail spectacularly.
I never said that they usually do. Learn how to read.
madtheory wrote: Tell me, did you just replace the spectacular failures in your Juno? I guess not. So how do you know they were broken? You didn't. So is recapping willy nilly some kind of therapy? Because it has no value for repair.
I already explained my reasoning very thoroughly. If you still don't get it, that's your loss.
madtheory wrote: Maybe you have improved the amplifiers you re capped, but where's your proof?
My proof is that the sound and performance of every amplifier I have recapped improved dramatically. I didn't need to do a bandwidth analysis to know that there was an improvement when it was so ridiculously obvious.
madtheory wrote: Yes, clearly capacitance is not the only parameter of a capacitor. But in most audio and related circuits, it's the only parameter that matters.
Flat out untrue.
madtheory wrote: If a cap is "out of spec", the evidence is in the performance of the circuit elements nearby. That is determined by the parameters given in the service manual, and the level of one's diagnostic skills.
Not always. Sometimes you can get a good idea, but the only way to really know that a cap meets spec is to test it by removing it from the circuit.
madtheory wrote: But given the lack of logic in your post, I guess maybe you're not too hot on diagnostics? PS I made that point clear so you will know I'm not patronizing.
I don't think you know what "patronizing" means.
Ya, caps are cheap, but replacing 30 of them is time expensive. How cheap is your time?
You're right, I do value my time. Fixing music gear is something I enjoy doing, so I make an exception for it. On the other hand, something that clearly is a waste of my time is arguing with people over nonsense on the internet. So, thanks for pointing that out. I think I'm done here.

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Re: Scored a Juno-60

Post by madtheory » Tue Oct 18, 2011 6:46 am

Get an oscilloscope and stop guessing with this stuff.

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Re: Scored a Juno-60

Post by Projectile » Tue Oct 18, 2011 7:01 am

madtheory wrote:Get an oscilloscope and stop guessing with this stuff.
I used to own two. Had to sell them when I moved. Been hunting for deals on craigslist.

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Re: Scored a Juno-60

Post by madtheory » Tue Oct 18, 2011 11:43 am

OK. Let me share some experiences. I have a pair of speakers from 1976. Decided to recap the crossovers a few years ago (two large Philips caps). I did the left one. Compared it to the right one. No audible or measurable difference. The data sheet for these caps states 35 years. I have it somewhere, I'll dig it out.

Quad 405, nice amp from the same year. Removed the LF filter caps and the limiter caps (which removes it from cct). Vast improvement in sound (just remember to mute speakers on powering!). PSU caps were not changed. It's been fine for 10 years since I did that. Job took about 10 minutes. Amp runs for 12 hours every day for most of its life.

I've owned 3 Yamaha CS synths- 1979, 1980, 1981. One I had for twenty years (bought used). Not a single cap changed, no issues at all with the synth, tunes perfectly, no noisy pots never blew a fuse.

I have an Amek BC2 mixer from 1985. Last serviced six years ago. Two DC blocking caps changed. Functions 100% perfectly.

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Re: Scored a Juno-60

Post by Altitude » Tue Oct 18, 2011 12:46 pm

You dont only recap because of changes in capacitance, you also recap because of the ESR of the cap goes up with age. This is actually worse since it can damage transistors down the line and is much harder to diagnose (although there are some diy ESR meters than can be built)

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Re: Scored a Juno-60

Post by madtheory » Tue Oct 18, 2011 9:24 pm

Yes, agreed 100%. The key here is to make an informed diagnosis based on the service manual, with the aid of the right tools (scope, meter, oscillator etc.) and replace only what you suspect to be broken.

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Re: Scored a Juno-60

Post by Mooger5 » Thu Oct 20, 2011 1:10 am

Altitude wrote:You dont only recap because of changes in capacitance, you also recap because of the ESR of the cap goes up with age. This is actually worse since it can damage transistors down the line and is much harder to diagnose (although there are some diy ESR meters than can be built)
I have just built one and I´m testing my stock of electrolytic capacitors. I´ve got 300 or so. So far, in 70 caps only one tested not OK. It´s a little 10uF/35V that was from a Matrix 1000. Measured capacitance: 8.9uF. Measured ESR: 10 Ohms!

What´s interesting is that there is a scientific paper that states that even brand new electrolytic capacitors have a limited shelf life before they can go out of spec while being kept in storage. Not to mention the ones that are actually working in a circuit. I´ll see if I can find it for reference. Well, I´ve bought a few caps some twenty years ago which I never used yet, and they test OK. I also salvage parts from dead audio equipment, including electrolytics, and I have to admit I´m surprised to find just one bad capacitor out of 70.

The good thing about ESR meters is that they can test capacitors in-circuit. And I was ready to recap the PSU of my Polysix with brand new Philips blue axials, but then the original caps tested great!
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