Univbe repair

[Jay]

Hi,

Didn't intend my first posting to be a plea for help but got asked to repair a broken Univibe last night.  It works but is making random clicks, pops, splatts etc. (not related to LFO speed).  First thought was power supply so I changed the 3 smoothing caps.  No joy.  Prodding round with a scope shows clicks and pops all over over the place but maybe these are getting back onto the power rail from elsewhere?

Sounds to me like a cap breaking down but difficult (impossible?) to find given that on the scope the clicks appear throughout.  

Given that its a valuable vintage beast I don't really want to just replace all the caps but I can't think of anything else.

Can anybody offer any suggestions please?  

Thanks in advance


Jay

[Jay]

Any takers please?!


Jay.

[Eb7+9]

... hard to say

you could have a "chatty" device exhibiting intermitent avalanching ... that would very likely feed through the psu line to the rest of the single-ended circuitry ... if there's a safe way to heat up each device, one at a time, sometimes that can exacerbate the problem and help isolate that situation ...

... the same thing could be said of internal resistor fissures, and cold solders ... I'd go in there and apply slight pressure on all contact nodes and resistors with the end of a chopstick ...a clean and dry one :wink:

just some ideas

... might eventually have to replace all transistors ... and resistors ...

Best of Luck !

~jc

[Jay]

JC,

Thanks for the advice.

I did try tapping all the caps/resistors/trannies but no audible result.

It is quite an old vibe - carbon comps, I've seen a later one with carbon films  - so not unlikely that something is on its way out.

I'll start with the caps and see how it goes.


Thanks again,


Jay.

[R.G.]

You may want to go read GEO (http://www.geofex.com), especially in this the Guitar Effects Debugging Page, which gives a set of suggestions for breathing new life into very old pedals. For very old pedals you have to cope not only with the immediate problem that's causing grief but also with the ..next.. thing that's going to break. If you do this well, the pedal will be reliable again for a long(er) while.

Go read it anyway, as there's more there than I'm willing to retype, but some salient things you'll find are:
1 - With something this old, replacing all the electrolytic caps is the first thing to do. Just do it. If it's not an electro failing now, one is certain to fail soon because they're all so old. You'll add decades to the life of the unit while you have it open and it's easy.
2 - Remelt all the solder joints with just a whiff of fresh rosin - core solder. Old joints that were marginal to begin with get worse with time. This is especially pertinent to old EH pedals, but all old ones benefit. You can save sufficient debugging time to make it worth your while, and more importantly make the pedal reliable again.
3 - Test all the pots, jacks and switches for proper operation with an ohmmeter. Mechanical things fail a lot, much more than electronic ones.

Only when you have those three things done go to work on the specific problem. The problem may well be entirely fixed. If not, go on to 4.

4 - Unsolder the collector of one transistor at a time, starting at the stage nearest the output. Listen - is it now fixed? If not, resolder the collector and go to the next transistor up the chain. You may unsolder the collector resistor for transistors having them. The idea is to turn off one transistor at a time. If the noise quits on one of them, something in that section is causing the grief. You can then look in that section for the problem. The problem may be a cracked resistor (CC's do this a lot), broken capacitor lead, cracked PCB trace, etc. If you find nothing like that, replace a the transistor whose collector lead being open made the noise go a way. Watch the pinout of the replacement!!

5 - If transistor easter-egging does not find the problem, you're down to very marginal cases. Check power supply diodes, poke at every single component with a wooden instrument, try letting it heat up. Look for intermittents in the power transformer.

If those don't find it, write me back.

[Jay]

RG,

Thank you very much for your tips.  As I said to the owner - if it was mine, I'd replace all the caps.  He's concerned about the lovely vintage sound being changed by this but as its currently unuseable.....

One I didn't try was the mains input.  Occured to me this morning that it could be a dodgy/dirty mains switch (or fuse holder).  I'll try bypassing this and going straight to the transformer (still got a fuse in the plug so happy to do that temporarily).

The vibe has gone back to its owner while I order some caps so it will be a week or two before I'm able to report back.

Thanks again for the excellent advice, its much appreciated.


Regards,



Jay.

[R.G.]

He's concerned about the lovely vintage sound being changed by this but as its currently unuseable.....

This attitude always makes me smile to myself, if not laugh outright. It recalls the scene in Spinal Tap when Nigel tells the interviewer not to touch the "original" guitar - in fact, not to even look at it.

I wonder if we could get people over this if we trained them to the idea that electrolytic caps are like very long-lived batteries - they wear out and need replaced or the equipment  becomes a piece of sculpture with zero usable function. No one I know of thinks their pedal is better for having its original battery in it, dead though it may be.

Sigh. There *is* something in the human mind that wants there to be mysterious magical *somethings*, isn't there?

[Jay]

I've told him electrolytics have a limited life span and that these ones - being nearly 40 years old - are way past that.  He's not so much worried about the authentic angle of having all original parts, more concerned about the sound being altered.

You're right though that people do desire that mysterious entity.  It s a placebo effect I think.  Give patients sugar pills and tell them its a miracle cure and some get better.  Give a guitar player a pedal full of carbon comps and vintage mojo and he may play better.


Jay.

[Eb7+9]

Sigh. There *is* something in the human mind that wants there to be mysterious magical *somethings*, isn't there?

Sigh. There *is* something in your mind that wants there not to be mysterious magical *somethings*, is there?

outside of abject logic ...

[RedHouse]

...I wonder if we could get people over this if we trained them to the idea that electrolytic caps are like very long-lived batteries...

That's exactly the analogy I use with the folks I deal with, none of which are even slightly electronics savvy, the batter thing is something everyone can relate to.

[R.G.]

Sigh. There *is* something in your mind that wants there not to be mysterious magical *somethings*, is there?

outside of abject logic ...

You say that like it's a bad thing.

Yes, there is. And it is called logic, abject or not.

Magic is a term for something that happens only inside the human brain.  The human brain constructs an internal image of what our eyes, ears, skin, nose and tongue tell us is happening. The internal image may or not may be complete and may or may not contain additional items which are  not independently detectable by other humans. There has never been a reliably recorded instance of these additional items being (a) detectable by other humans or (b) having any independently detectable effect on the outside world. It's entirely inside the head that detects it. It's NOT usable as a way to affect the outside world. Music is about creating effects inside the listener's head, so music may be considered magic, but it's a private magic, not verifiable outside the listener's head. And as we all know, each listener hears something different (yes, I can cite the research).

But you can look up more formal definitions of magic. Maybe you should.

Independently verifiable events, cause and effect, the physical laws that Mother Nature gives us are what got us out of caves and into whatever mess we're in today. To date, I'm unaware of any event in human history that can be shown to have happened as a result of magic as opposed to logic and discoverable (if not already discovered) physical laws or the math of quantum physics and probablity. Not one.

And as an engineer, yes, I have an internal conviction that events that occur, operation of physical devices and such will be not only explainable but predictable by the laws of nature we have either discovered or can discover, not by a sideways step around of these laws. While I do not exclude the possibility that there are laws we have not yet found, in the tiny microcosm of electronics for effects, there are likely to be vanishingly few.

The very concept of magic implies a denial of predictability - that is, that sometimes things happen that are not predictable from the events preceeding them. The concept of magic says that two plus two is sometimes NOT four.

I grant you that our current understanding of quantum mechanics is that individual events involving quantum mechanical entities are not predictable on an event-by-event basis because of the uncertainty principle; however these events are predictable on a statistical basis, and very closely. That's the point of stochastic processes - they are predictable by the laws of probability.

Those events are not usually detectable in the non-quantum mechanics world. I can think of examples where they are, but in the main part, no. And not in the world of music and effects.

So back to two plus two is sometimes not four. Not only that, magic requires that someone external to the event - the magician - be able to control the times when two plus two is not four. That external control is what sets the theoretical concept of magic apart from stochastics. Think what the existance of magic would mean. We would not be able to rely on any event to happen as expected, as there might be some magician somewhere perverting the event. Water might flow up hill (i.e. gravity might not hold); any photon striking you might be a death ray; lighting a cigarette (while a bad enough event in and of itself) might set off a modest yield matter-antimatter bomb in the cigarette. Could happen - it's magic!

Or did you think magic only happened in subtle, happy events?

I think the best working definition of magic as it happens in the real world is that magic is a technology you don't understand. To accept something by labeling it "magic" is to make the decision that you either are currently incapable of grasping the laws that control it or that you will not take the time to understand it.

I vastly prefer thinking that I have not yet understood the laws controlling any given event that I don't understand rather than labeling it as magic, a denial of predictability and an abdication of my ability to understand. If you prefer to think that there are events that you simply cannot understand or refuse to understand, go ahead. We differ that way, I guess.

Separating wheat from chaff, fact from fiction, causality from magic are all logical operations. To date in human history, the logicians seem to have been on the accurate side every time. The magicians seem to be thinning out as more physical laws are discovered.

[Eb7+9]

Not a bad thing RG ...  just pulling your left brain ...

... interestingly, the search for absolute "formal" provability came crashing down when some logician proved that you couldn't prove mathematics was without contraditions ... this sent researchers into cross-discipline forays looking for contradictions rising from inter-field comparisons - which lead to the forming of the branch of mathematics known as Category Theory ... unlike in the error-measurement based physical sciences, in its truest sense, provabilty can only exist in Mathematics as a methodoligical process ... both sufficiently and necessarily justifying and defining itself in that process ... that's why the difinition of a mathematician as someone who proves things sounds weird to some people - they are, in a greater sense, trapped servants to the requirements of a most strict formal system ... the same way a music student can become trapped victim to the notes on a music sheet ...

So, imagine if in a formal field where difinitions are super clear (not necessarily simple) ultimate certainty can't be established completely (which is tantamount to knowing there's no guarantee the foundation we build upon won't give way one day- similar to the Greeks with their rational number system) then where does that leave everyday life with myriads of loose definitions and agreements on most things ?

... obviously, if we're not careful enough to overlook basic assumptions about language then conflict is bound to result ... as a result of these consequences, we risk becoming the servants of language and not the other way around as it should be ...

But you can look up more formal definitions of magic. Maybe you should.

no need to - and from the above no point to ... most of us musicians experience that when jamming once the ESP thing kicks in  ... even though many have done awesome work (Jung, Koestler, ...) formalizing its description, in the end it's really the stuff of personal experience - it's like food and sex ... to Mikmah artist Norval Morriseau it's called the House of Inventions ... it's there to be experienced, not formalized and overly discussed ... sadly, the fact this potential for confusion is not openly mentioned leaves open possibilities for many things to take place which otherwise wouldn't happen - and vice versa ...

seems to me the problem with extrapolating formal thinking out into the informal settings of everyday life is you can get carried away leaving "content" behind ... leading to a form-without-content scenario ... we see this  in misguided parenting,  law enforcement abuse, tacit use of punishment, misguided teachings and movements ... symptoms of unconscious living  ...

I always wondered if the burning Strat at Monterey was bout trying to break our collective over-attachment to formalism ...

... just pulling your right brain ...

~jc

[moosapotamus]

Well, this is quite an interresting discussion to have while Jay is waiting for his caps to arrive.
Maybe Godot will show up sometime soon, too.

I always wondered if the burning Strat at Monterey was bout trying to break our collective over-attachment to formalism ...

Consciously or not, I'd say that is precisely what it was about. I mean... like, duh... what else could it possibly have ultimately meant... like, maybe he was just cold? But, I'll bet that no one ever, intentionally, burned a UniVibe... :shock:

I think magic, like art, is in the eye of the beholder. But, I guess that's basically what both of you are already saying, anyway.

~ Charlie

[Jay]

Well, while you guys have been on a Magical Mystery Detour I've been Vibing.

Bypassed the mains switch/fuse/lamp.  
Re-soldered everything.
Changed all the electrolytic caps

And.....and......

Still crackles and pops like a frying pan.

So, I think now its down to the RG step number 4 of turning off a stage at a time to try and isolate the culprit.

Going to have a break from this and tackle it again in a couple of weeks.  

I'll post another exciting update then......



Jay.