Bare bones Klon powering down issue

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tome.talevski
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Post by tome.talevski »

Hello! I’ve just built the bare bones klon 9v version:

https://tagboardeffects.blogspot.com/20 ... 7278215494



... however there’s an interesting issue that I have not encountered before.. within 30 seconds of the circuit being on (and working fine) it slowly fades out. The LED remains on. When I disconnect and reconnect a power cable it resets, works for 30 seconds then turns off again.

I’m wondering whether this points to a specific perhaps obvious issue that explains the above?

Cheers

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deltafred
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Post by deltafred »

There is possibly a fault somewhere round the op-amp bias part of the circuit.
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tome.talevski
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Post by tome.talevski »

deltafred wrote: 19 Nov 2020, 09:15 There is possibly a fault somewhere round the op-amp bias part of the circuit.
Hey, thanks for your response.

I’ve had enough experience biasing transistors but never an op amp. Is there a specific resistor connected to an op amp pin i should be looking at?

Here are some readings:

TL072

1: 4.59
2: 4.59
3: 3.60
4: 0
5: 4.58
6: 4.58
7: 4.60
8: 9.19

TLC2262

1: 4.58
2: 4.58
3: 4.58
4: 0
5: 0
6: 2.30
7: 0.04
8: 9.19





Thanks

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plush
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Post by plush »

I've had a similar issue with one of my latest builds (not a Klon related).

One of the opamps started to slowly drift away after some time, clipping the bottom half of the sine wave. Resetting the power helped for a brief period, untill the opamp started to drift again.
The fun thing is, that both Vcc and VB were not affected. IC itself was not an issue either, since I've tried multiple of them,

Turns out, there was some parasitic capacitive feedback, affecting the 2nd half of the opam, which was introduced by a broken trace (it developed a microscopic crack due to surface tension after the reflow) and defective component in feedback loop. So, the 2nd half of the opamp was internally oscillating and affecting the 1st half. Crazy shit.

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deltafred
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Post by deltafred »

Can you post the schematic you used.
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Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012

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tome.talevski
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Post by tome.talevski »

deltafred wrote: 19 Nov 2020, 17:18 Can you post the schematic you used.
Here's a link to the Vero layout I used. :)

https://imgur.com/rTRSAHA

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Post by deltafred »

tome.talevski wrote: 19 Nov 2020, 19:45
deltafred wrote: 19 Nov 2020, 17:18 Can you post the schematic you used.
Here's a link to the Vero layout I used. :)

https://imgur.com/rTRSAHA
Yes but a vero layout is not a schematic.

Someone with a bit of experience can read a schematic and see at a glance, a vero layout has to be reverse engineered.
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Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012

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tome.talevski
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Post by tome.talevski »

deltafred wrote: 19 Nov 2020, 21:52
tome.talevski wrote: 19 Nov 2020, 19:45
deltafred wrote: 19 Nov 2020, 17:18 Can you post the schematic you used.
Here's a link to the Vero layout I used. :)

https://imgur.com/rTRSAHA
Yes but a vero layout is not a schematic.

Someone with a bit of experience can read a schematic and see at a glance, a vero layout has to be reverse engineered.

The only schematic I can find is the one attached to the original 'bare bones klon' thread on this site...which is where the Vero layout comes form I believe. I can't manage to save it large enough although I pasted the link below.


viewtopic.php?f=13&t=7526&hilit=simplified+klon

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Post by tome.talevski »

I may have just figured it out.. after resoldering I discovered one of the jumpers that shares a hole was a bit loose.. after resoldering properly all seems to work fine! Interestingly these jumpers connect to the 0 readings of IC2.

Thanks for taking the time to respond and apologies for not having discovered this sooner!

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Post by deltafred »

Good to hear that you got it working.

For info, referring to mictester's schematic on page 1, the bias voltage VB is created by the potential divider R29 and R30 and decoupled by C47. If any of these components are faulty (C47 leaky being the most probable) or there are bad solder joint/s then it can cause the signal to fade out as the bias voltage drifts towards the opamp supply rails.
Politics is the art of so plucking the goose as to obtain the most feathers with the least squawking. - R.G. 2011
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012

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