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Keantoken's CFP cap multiplier
Keantoken's CFP cap multiplier
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Old 11th March 2016, 04:26 AM   #901
keantoken is offline keantoken  United States
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Hey guys. There is a problem with the DirtyPCB boards. Due to problematic layout, they have a problem with oscillation.

Keantoken's CFP cap multiplier-dirtykm-oscillation-png

I have wanted to make my own boards for the KM, but when these PCBs came out I figured that ship had sailed. But the layout is mostly done. I figure now would be a good time to print if you guys are interested.

Keantoken's CFP cap multiplier-pkm-compact-layout-png

The KM design for this board will be different. It has better filtering and doesn't have all those protection diodes - they never worked anyway. The PCB can be mounted flat to a heatsink with a standoff or if you want to use a floating heatsink, mount it under the board so it's away from the capacitors.

To fill the board you simply look at the circled pins. They must be the same polarity as your output voltage. So if your output voltage is positive, all the circled pins are positive. It fits terminal blocks and works up to 50V. It could also be used with D4xH11G for 2A output or so.
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File Type: png DirtyKM-oscillation.png (290.6 KB, 1023 views)
File Type: png PKM-compact-layout.png (22.7 KB, 1011 views)
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Last edited by keantoken; 11th March 2016 at 04:39 AM.
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Old 11th March 2016, 04:44 AM   #902
TNT is offline TNT  Sweden
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Great! Will you do DirtyPCB?

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Old 11th March 2016, 05:28 AM   #903
keantoken is offline keantoken  United States
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I want to sell them and see if I can earn myself a few gumballs.
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Old 11th March 2016, 05:29 AM   #904
TNT is offline TNT  Sweden
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Good on ya'!!

I'd be interested.

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Old 11th March 2016, 05:35 AM   #905
av-trouvaille is offline av-trouvaille  Netherlands
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Oh well, a set of Dirtypcb's is on its way to my postbox. Would you please have a hint on how to minimize the risk of oscillation when mounting the parts? Or should the pcb's simply be binned?
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Old 11th March 2016, 06:32 AM   #906
Destroyer OS is offline Destroyer OS  United States
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Keantoken's CFP cap multiplier
Quote:
Originally Posted by av-trouvaille View Post
Oh well, a set of Dirtypcb's is on its way to my postbox. Would you please have a hint on how to minimize the risk of oscillation when mounting the parts? Or should the pcb's simply be binned?
Even if they worked they're not as good.
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Old 11th March 2016, 06:52 AM   #907
av-trouvaille is offline av-trouvaille  Netherlands
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I am not shure whether that is an answer to what I asked.
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Old 11th March 2016, 06:56 AM   #908
Krissz80 is offline Krissz80  Hungary
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Quote:
Originally Posted by keantoken View Post
Sorry I missed this. Can you tell me why you made those changes? If anything the 10nF cap should go on the B-E of the BD140. And I think I have seen more than one KM using the BD140 that oscillated.

The KM should have capacitors close to both the input and output, but 100nF film caps are unnecessary and sometimes will even cause oscillation.

100nF for decreasing the Esr of the Elkos at higher frequencies.
10nF for the BC337 is for prevent oscillation that maybe occours when the transistor gets older.

Maybe BD140 needs 10nF too, but my K-multi just went wrong today morning.
The output voltage is 6,5V with 14,2V input.
I'll change the BD140 to a TIP42, and later to the D45H11.
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Old 11th March 2016, 07:13 AM   #909
keantoken is offline keantoken  United States
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They can be made to work if you wire C1 directly from Q1's base to the ground pin of C5, and do the equivalent for the negative side.
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Old 11th March 2016, 07:24 AM   #910
keantoken is offline keantoken  United States
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Quote:
Originally Posted by Krissz80 View Post
100nF for decreasing the Esr of the Elkos at higher frequencies.
10nF for the BC337 is for prevent oscillation that maybe occours when the transistor gets older.

Maybe BD140 needs 10nF too, but my K-multi just went wrong today morning.
The output voltage is 6,5V with 14,2V input.
I'll change the BD140 to a TIP42, and later to the D45H11.
Remove the 10nF caps, in some circuits they are a last resort but are rarely optimal for a fast or low noise circuit. The BC337 should not age, if so then they have been abused.

The 100nF can actually cause oscillating by making a peak in the source impedance. I suggest instead you use Wima 10uF or Vishay MKP416 1uF. This will go much farther towards the goal of low ESR film bypass.

wima 10uf WIMA 10 uF 5 mm Film Capacitors | Mouser
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