Author Topic: Peaktech 4250 AC/DC current clamp teardown and repair.  (Read 546 times)

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Offline The Soulman

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Peaktech 4250 AC/DC current clamp teardown and repair.
« on: January 13, 2018, 07:40:01 am »
I've owned this clamp now for a while but never was satisfied with the low current readings there was to much noise and drift to be useful.
After reading here:  http://www.eevblog.com/forum/testgear/hantek-cc-65-acdc-current-probe-teardown-and-testing/
about insufficient decoupling in the Hantek CC-65 I decided to open up my (similair but not exactly the same) Peaktech.
And discovered there weren't any electrolytic capacitors fitted at all!  :-//
Fitted some 33uf 35V caps because that is what I had and it functions much better now.  :-+
Anyone has an idea about who could be the OEM of these clamps and what each of those trim pots does?
No point in making a point just to make a point, that would be pointless.
 

Offline The Soulman

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #1 on: January 13, 2018, 07:41:06 am »
More pics..
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Offline The Soulman

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #2 on: January 13, 2018, 07:42:14 am »
Caps fitted..
No point in making a point just to make a point, that would be pointless.
 
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Offline schmitt trigger

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #3 on: January 31, 2018, 04:08:40 am »
I have that exact same probe!
Between today and tomorrow I will open it up and see if it also has the same capacitors missing.

To your question, I see a pair of probable answers:
-cost savings. When a company sells these so inexpensively, every cent counts!
-manufacturing error. The board is a mixed mode SMT/TH component assembly. Perhaps the TH components are hand fitted, and they forgot installing the electrolytics.
« Last Edit: January 31, 2018, 04:15:40 am by schmitt trigger »
 

Offline The Soulman

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #4 on: January 31, 2018, 04:40:21 am »
I have that exact same probe!
Between today and tomorrow I will open it up and see if it also has the same capacitors missing.

To your question, I see a pair of probable answers:
-cost savings. When a company sells these so inexpensively, every cent counts!
-manufacturing error. The board is a mixed mode SMT/TH component assembly. Perhaps the TH components are hand fitted, and they forgot installing the electrolytics.

Cool, yeah my idea is that the guy or gall responsible for fitting them came in late that day or had a long lunch break...
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Offline mcinque

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #5 on: January 31, 2018, 09:18:54 am »
Maybe Hantek? I found that current clamp under various brands (Pico for example) and two different versions (oscilloscope and dmm).

In my experience, Peaktech only rebrands instruments and sell them at higher prices, without ANY added value.
I'm basically still a rookie and because of this, even with the best intentions, I often say bullshit :)
 

Offline schmitt trigger

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #6 on: January 31, 2018, 09:58:13 am »
I believe this is a trend for many of the lower cost test instruments.

I've a differential probe which I found that Dave had made a teardown analysis video.

However, Dave's probe brand and model are different from mine, although inside they are essentially identical.
 

Offline technogeeky

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #7 on: February 01, 2018, 03:16:07 am »
I have two questions:

* is there any reasoning for the exact value of the electrolytics?
* is there any reason to use some other type of capacitor for noise purposes? MLCC? tantalum? etc?

 

Offline The Soulman

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #8 on: February 01, 2018, 03:59:17 am »
I have two questions:

* is there any reasoning for the exact value of the electrolytics?
* is there any reason to use some other type of capacitor for noise purposes? MLCC? tantalum? etc?

I used what I had that would fit (2,5mm spacing, 5mm diameter, 12mm height) for me that happened to be 22uf 35V Yageo "low-esr".
Just to see what would happen, I liked what happened so left them in.  :)
If the design is reverse engineered than each capacitor could be optimized, perhaps off-set and bandwidth performance could also be improved.
No point in making a point just to make a point, that would be pointless.
 

Offline schmitt trigger

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #9 on: February 04, 2018, 06:44:06 am »
Mystery solved!
Finally on this weekend I had some spare time to open my probe.

I found that those empty capacitor holes are in parallel with the SMT tantalums nearby.

As a fact, one can read C7 and C7A, C1 and C1A.............meaning that you could fit either a SMT or TH component on the board depending on availability.
 
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Offline technogeeky

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #10 on: February 04, 2018, 07:20:36 am »
Mystery solved!
Finally on this weekend I had some spare time to open my probe.

I found that those empty capacitor holes are in parallel with the SMT tantalums nearby.

As a fact, one can read C7 and C7A, C1 and C1A.............meaning that you could fit either a SMT or TH component on the board depending on availability.

To me, that really begs the question of why they don't include more capacitance. So the through hole electrolytic capacitor spots are just alternates for the tantalums they included. But surely if they included larger tantalums, the noise would be lower as this modification suggests.

I really don't understand.
 

Offline SeanB

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #11 on: February 04, 2018, 08:31:45 am »
Larger value tantalums would be expensive, and possibly not usable in the PNP process they have due to size or mass, so they used either ones on the machine already or the largest value they could reliably place instead. Going for the TH part and hand soldering would be more expensive as well, and using SM electrolytics would probably not work either as they would have the same mass and height limits that were there for the other caps already. In any case 22uF added to the existing 10uf and 22uf ones would be a good improvement.
 

Offline The Soulman

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Re: Peaktech 4250 AC/DC current clamp teardown and repair.
« Reply #12 on: February 04, 2018, 09:10:13 am »
Mystery solved!
Finally on this weekend I had some spare time to open my probe.

I found that those empty capacitor holes are in parallel with the SMT tantalums nearby.

As a fact, one can read C7 and C7A, C1 and C1A.............meaning that you could fit either a SMT or TH component on the board depending on availability.

Looking at the pics it is actually quite obvious,  :-[  when time comes I will try to draw a schematic of this thing, gotta know what each of those pots do..
No point in making a point just to make a point, that would be pointless.
 


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