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Old 26th October 2013, 03:48 PM   #11
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What we are all wondering is how will battery life be seriously compromised without a reservoir capacitor?

I can only assume that you meant that if it was unstable, or even oscillating supersonically - battery current would be increased?
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Old 26th October 2013, 05:12 PM   #12
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Quote:
Originally Posted by John Audio View Post
What we are all wondering is how will battery life be seriously compromised without a reservoir capacitor?

I can only assume that you meant that if it was unstable, or even oscillating supersonically - battery current would be increased?
Any electronic circuit is designed on the basis that there's a low impedance AC path between the supply rails, and that the supply itself has a low impedance.

The capacitor across the supply fills those two requirements.

Without the capacitor (or if it fails) it 'may' work when the battery is absolutely brand new, but in a relatively short time it will fail to do as, as the source impedance of the battery increases and the circuit starts to fail.

Remote controls are probably the best example? - if the capacitor goes O/C (and I've changed many over the decades) - the battery life drops from 2-3 years to only 2-3 weeks. If you replace the capacitor, the existing batteries work fine again, but not without it.
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Old 26th October 2013, 06:44 PM   #13
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You have the "right" answer for the wrong reasons.

No way can the lack of a capacitor pull more current from the battery and cause its early failure!

What happens is the battery internal impedance goes up with age and, without a parallel charge storage cap or higher ESR of the existing one, the peak current to fire the infra-red leds is not available!

So the battery no longer works in that circuit with its higher ESR.
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Old 26th October 2013, 09:48 PM   #14
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Nigel Goodwin View Post
In what regard?, no nonsense there at all.
Hi,

Its all nonsense for a battery powered fuzz box.

Battery life - nonsense.
Motorboating - nonsense.
Instability - generally nonsense if the board has suitable
properly placed rail decoupling caps, typically 100nF.

rgds, sreten.
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Last edited by sreten; 26th October 2013 at 09:50 PM.
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Old 26th October 2013, 10:44 PM   #15
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if the original poster can post the schematic it would be helpful
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Old 27th October 2013, 10:09 AM   #16
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Quote:
Originally Posted by cliffforrest View Post
You have the "right" answer for the wrong reasons.

No way can the lack of a capacitor pull more current from the battery and cause its early failure!
Which I never suggested.

Quote:

What happens is the battery internal impedance goes up with age and, without a parallel charge storage cap or higher ESR of the existing one, the peak current to fire the infra-red leds is not available!

So the battery no longer works in that circuit with its higher ESR.
I never suggested anything different - and even said that fitting the essential capacitor would allow you to re-use the battery.

But it's not just remote's, that's just an extreme example, it applies to almost anything electronic.
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Old 1st November 2013, 01:39 AM   #17
JMFahey is offline JMFahey  Argentina
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What Nigel says clearly is that a low supply impedance is good/necessary (take your pick), doubly so in a *high gain* (any doubt about that?) , *crude* design (any doubt about that?) like a Fuzz.

An old tech 9V battery, carbon zinc is what we are talking about, will start with a relatively high internal resistance which will only go up, never down.
Which is a *known* cause for instability.

So one of those batteries will last, say, "X" days because instability raises its head, but many more days with the cap added.

Making so much fuss about that cap, which by the way was used from the beginning, as shown in the original schematic , well, *that*'s nonsense.
Or having very little to do.

Increased current consumption was never mentioned or implied, don't know where was that pulled from, *but* longer "usable" or "practical" life.

Which is the point, of course.
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Old 9th November 2013, 03:53 AM   #18
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Click the image to open in full size.

OK, here's the image. I finished the prototype. It "sort of" works, but the problem is very low gain. Even with the 2 pots all the way up, the sound volume is attenuated by more than 60% when running the guitar into the box vs running it (bypassed position) directly into the amp. When going in "notch" position, there's virtually no sound at all, but skip that for now (that makes me assume the problem is "earlier" in the signal path). As you can see, the part specs are very vague. I used MPS-6531's for all the transistors rather than 2N2222's, as that's all I had available. I'm wondering if the problem is in the transistors, or perhaps a few of the resistors can be tweaked. Incidentally, I used a pair of 1N4001 diodes for the clippers near the bottom left. As far as the resistors go, could I try cutting down the 22k input resistor, or perhaps the ones around the first two transistors (proportionately to each other) at the top left? And which stage (Q1/Q2) or (Q3) or (Q4/Q5) (I'm assuming Q6 is doing its job) would be most suspect for causing performance issues like this? I'm not an engineer, and not quite the gizmo tech freak I'd like to be, but very good at construction, so any help is appreciated
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Old 9th November 2013, 10:13 AM   #19
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Yes, In misread the reply. Apologies to Nigel.
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Old 9th November 2013, 11:52 AM   #20
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You need to find out where you're losing the signal, if you don't have a scope, then use your amp as a signal tracer. For a start feed the amp from the output of the 'drive' control, this should be considerably louder than direct from the guitar.

So try that, and report back.
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