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Hi Wolfgang,  :)

I know that the current limitation is not optimal....
I don't need that for this power supply.
As you already explain it, it is this kind of simple solution only meant for "calamities".
I am fully aware of the control properties and their temperature sensitivity.

A large part of my life (> 50 years) I often use the current limitation differently than many other people do.
When I connect a D.U.T. to a Power Supply, I first think about the current that will or may be consumed.
Then I set this current and whether this is 50mA or 55mA does not matter so much to me, even if the current drifts from 48 to 53mA, so what...
When I need a very precise current I almost never use a power supply but a current source.

And I'll repeat it again, I won't charge a battery with power supplies and certainly not without using a diode.
I think it doesn't happen more than twice a year that a battery is charged from a power supply in my LAB, I use battery chargers for that.  :)
And a LED is always tested here via a series resistor, or via one of my multimeters (TEK DMM4050)
I have 15 power supplies here in my LAB and if I need precision current limitation then I do so with a power supply type that is suitable for that.

This design I show here puts more emphasis on the smallest possible abberations and as little noise as possible and a reasonable DC drift.
It is not a "One size fits all" power supply.
And again, every user of measuring equipment must know the characteristics of this equipment if you want to make as few mistakes as possible.

If I want a more precise current setting, I can always choose at least two power supply's that are on my workbench, that is the Rigol DP832 and the Agilent 6632B.
But as I said, that almost never happens especially for that purpose.

I Love/Hate my Rigol DP832, this has a high resolution for both current and voltage and this together with the power display.
But the 470uF over the output terminals don't make much sense if it is for example set to 24V and 20mA maximum current.
The charge of the 470uF capacitor is dumped into the DUT when something goes wrong.
What is the point of a precise 20mA current limit then? so... the user must know the characteristics of this equipment if you want to make as few mistakes as possible.  :-DD

But I would like to hear more good comments, we learn from that.

Kind regards,
Repair / Re: HP 3440a digital voltmeter repair/troubleshooting
« Last post by valley001 on Today at 07:47:49 am »
OK, no C2 sub in my parts bins but new part arriving Friday.

Q3 is here for the A3 board, I plan to remove old Q3 and test the associated cap.    Is there anywhere else I need to look so I dont fry the new Q3?
The military grade counterpart of the 74 series is the 54 series.

The first document only list a few components, already found this very short list (just 1 page) which listed none of the components I have. I knew the 54's are mil grade counterparts of the 74's, already got a few 54's in the same collection. The second document is useless for me, it is nothing more than a two column list where e.g. JM38510/31101BFA is cross referenced to...... JM38510/31101BFA....

"This search provides a cross-reference of microcircuits covered by Standard Microcircuit Drawings, MIL-M-38510 specifications and Vendor Item Drawings":

This site did not popup because of some HTTPS certificate errors. Now accepted the error temporarily so I can access the site, seems very useful. Not a cross reference document to be used offline but at least a way to see what those 'mysterious' part-numbers actually refer to. I have e.g. some JM38510/01309BEB components, although this site does not find the BEB variant it does tell me M38510/01309BEA is a SL54193/BEA. I'm sure I can safely assume the BEB variant could be a SL54193/BEB  ;)

Thank you helius and rfeecs  :-+
All of a sudden it became the almost unlocked version for 2k usd.  :-//  ;)
Do you see on what part of text I have reacted? Do you get it?

Not really. You've presented a bipolar solution that doesn't really help the OP (far too large voltage drop). Then you've referred to "unobtainium" JFETs, as if it is important to present a current within +/-1% to an optocoupler. After that you lost me.

The JFET solution is not precise, but will work down to almost 0 V voltage drop.

Test Equipment / Re: DS1054z No waveform on any channel
« Last post by realitycomputer on Today at 07:42:17 am »
Well,  after being really disappointed at the sudden death of my oscilloscope, and getting nowhere with Rigol for weeks, I'm finally geared back up to have another look.

As to the last post...... It doesn't seem to want to let me write to the filesystem.
The buttons are grayed out (Save, etc) I will try it with a USB stick......
(I should be able to save to the internal storage though, shouldn't I ?

I've done a "factory reset" of software, via LAN.
I've done the "fifth key down" reset - back to Chinese language, etc.

So now I'm really hoping that some of you might like to throw in some ideas, or even test procedures I can follow.

As a re-cap, basically I am getting no traces at all on any of the four channels.
(see earlier pics)

I am just a beginner hobbyist and am out of my depth here!
But I am capable of carrying out tests and measurements!

Maybe someone has an open DS1054Z and could give me some measurements I could use as a comparison base?

What could possibly knock out all 4 inputs!??

I'd appreciate any help at all!
Thanks for any suggestions.

Sample image

OMG - that 3478A has the special anti-gravity "option G".   :-DD

Didn't you know? The FW on the 3478A is written in Python.  :-DD


Hallo Mr. Liv and all who follow this tread.

I'm looking for someone who has a spare set of PCB's that i can purchase?
If no one has, then maybe someone is willing to place an order for a small production together to minimize cost and waste?
Third option would be for someone to be wiling to purchase a finished PSU or a kit from me?

Any help would be greatly appreciated.

Thank you all in advance  :-+
Metrology / Re: LM399 based 10 V reference
« Last post by Kleinstein on Today at 07:39:32 am »
300 Clock cycles for the fractional divider sounds like quite a lot. So I assume this would be C code. If it is just die divider and not much interface via UART, one could write ASM code. For a different project I have done a fractional  before - AFAIR the ISR was more like 20 cycles. So the power savings due to sleep mode could get more efficient. However it is still the oscillator running.

I don't think one would need a prescaler at the timer - this does not make much sense, it would mainly give away some resolution with no  savings in current consumption.
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