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Test Equipment / Re: Testing 75 ohm signals with 50 ohm gear
« Last post by Someone on Today at 11:27:54 AM »
I had started a thread about how to terminate a 75Ohm transmission line....
As I said, this is new territory  - so speak slowly  :-DD
The answer is in that older thread already. You can build an "ideal" test fixture with perfect transmission lines at 75ohm and then de-embed the cables and fixture when you measure the DUT. Its easier when the VNA automates this for you but its still possible to do manually if you can't afford the modern tools, and design of the test fixtures allows you to balance the important characteristics for your application.
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General Chat / Re: LED lit footpaths to protect zombies from themselves
« Last post by Cerebus on Today at 11:27:09 AM »
I ,on the other hand,find it amazing that others of my sex seem to think that leaving the "dunny seat" up is some sort of 'badge of office".

I thought that was the accepted norm 'down under' so as to make it easier to check for nadger biting spiders before you sat down.

Maybe there is a sub-species of blokes who get through life with only peeing.

There are, they're called "management" and they're full of ...
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EEVblog Specific / Re: EEVblog #982 - HP54616B 500MHz Oscilloscope REPAIR
« Last post by snoopy on Today at 11:26:33 AM »
The 1NB7-8353 ADC hybrid is also used in the HP 16534A scope card in their modular logic analyzer line.  I recently repaired a couple of them and one had a bad hybrid.

Of course I couldn't resist taking the top off.  Photo below.  I cracked the substrate in the process and also had to use quite a bit of heat.  Some of the caps might have reflowed and shifted a bit.

You can clearly see the ADC on the right and the 32k circular buffer memory on the left.  Someone already pointed out the piece that cracked off on Dave's was the input transmission line which you can see here goes directly to the ADC.


I bought a couple of ADC replacements from the $45 guy on ebay, watronics.  He's a retired HP/Agilent scope engineer and a nice guy.  No affiliation; just a satisfied customer.
I wonder if there is any way to build an equivalent circuit using modern parts on the same footprint with FR4 substrate material?

Probably no which is why the low end scope manufacturers have not been able to offer something economical in the 500 MHz and above category ;)
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Repair / Re: Another Power Supply
« Last post by OpenCircuit on Today at 11:26:11 AM »
Black diode (D11)  read 534/1 when removed from circuit. ZD2 still shorted. Main cap indicates thermal damage where one spot directly corresponds to Th1. D35 also shorted. Seems this PSU is a mess as well.
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If those are connected, then everything else looks fine...
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I've heard that the Rigol 1054Z takes a second or two to update after moving the waveform up and down, which would be a big annoyance for me.
They can be slow to respond if you've set a long memory depth or enabled maths or display settings vector/dots/interpolation/filtering so its often up to the user to balance performance to their preference. This has been common on most digital scopes for some time.
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Test Equipment / Re: Bunch of keysight U1252B meters around
« Last post by bitseeker on Today at 11:22:07 AM »
However when I push the batter test the bar graph advances to 2.6 on the display.  Took the battery out and measured the terminal voltage  at 6.7V.  Is this to be expected?

The bar graph display is 0-100% for battery charge level, rather than voltage.
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General Chat / Re: LED lit footpaths to protect zombies from themselves
« Last post by vk6zgo on Today at 11:18:13 AM »
There is becoming an endless list of I CAN STOP DRAGGING MY FEET WHEN WALKING = so make the ground perfectly flat for me ,
I CAN NOT PARALLEL PARK = so make the car park for me ,
I can parallel park, but I hate doing so, as it annoys other road users with someone "propping" in front of them & farting about.
Of course, this would not be solved by letting the car "fart about" for me! ;D
Quote
I CAN NOT BE BOTHERED TO LOOK IF THE TOYLET SEAT IS DOWN = so leave down for me - EVEN THOUGH I WILL NOT LEAVE IT UP FOR YOU ,

I ,on the other hand,find it amazing that others of my sex seem to think that leaving the "dunny seat" up is some sort of 'badge of office".
Hell, 30 or so % of the time, I go there for "number twos", so need the seat down myself.

Maybe there is a sub-species of blokes who get through life with only peeing.
I don't know what they do with the other stuff-------blow it away in dust or something! ;D
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Projects, Designs, and Technical Stuff / Re: Dawn operating system
« Last post by Wilksey on Today at 11:17:21 AM »
One of the "features" of this "revolutionary" OS is...wait for it...CPU Hotplug!  :-DD
Oh, transparent screens, they are a must these days, and don't forget the peer to peer wireless networking using geolocation!  All good and clever stuff!

They state it is "easy" to create hardware for this OS, yet they can't find any.  :-/O
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Other Blog Specific / Re: #110 mail Time Overload
« Last post by Radio Tech on Today at 11:14:52 AM »
You must be right on that.  I do not find them that good myself. Just an average guy doing what many others do.
Thanks Sue
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