AD584JH chinese voltage reference board

I bought some time ago a cheap AD584JH voltage reference board from the usual online auction site.

It is a couple of weeks that the board is powered on and measured by my HP3456A while the temperature of the room is measured by a DS18B20.

Moreover the Solartron 7159 is measuring the output voltage of the power supply that powers the voltage reference board.

I am just saving the data once a minute but it is a nice exercise with GPIB. I hope to write soon an R script to get some nice graph of the data.


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Re-streaming an ONVIF IP camera stream with ffmpeg and VLC

I had to test work done on an ONVIF IP camera and so I needed a way to see whatever the camera was streaming.

The first catch was that I couldn’t use any software that worked with the camera mainly because there were very few that worked or seemed to work.

The second catch was that I couldn’t be bothered to prepare an appropriate software infrastructure for just a test.

Third catch, the network was a bit complex so I couldn’t just use directly VLC.

I wanted a one line solution. I knew that ffmpeg could save the IP camera stream to a file and I knew that VLC could stream a file wherever I wanted.

One line solution that mostly worked for me:

ffmpeg -hide_banner -loglevel panic -i rtsp:// -codec copy -f matroska - | vlc - --intf=dummy --sout '#rtp{sdp=rtsp://}'

Your mileage may vary, but I think it is a good starting point. It worked on a CentOS 7, ffmpeg 3.4.7, VLC 3.0.8


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Happy 2020!

Happy New Year to everybody.

The last nice round year is another year nearer. There is hope I’ll see it, a real privilege as the last one was a long bit ago while the one after the next one is really a long way into the future.

So, if everything goes according to the plan, I will get to see it together with you, dear readers, something that I think the majority of mankind didn’t see and will not see.

By the way, I am actually also headed to my probably last, nice, round birthday which is happily nearer than 2048.


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Solartron 7150 added to the stack

Solartron 7150

Solatrton 7150

Now the trio of my 5.5 digits or better DMMs is working and logging which means I am out of IEEE 488 cables which means I ordered two more as there is a lot of my equipment that is really asking to be connected to a NI GPIB card.

Just a little something about the Solartron 7150: the front inputs and the back inputs are in parallel so you have to be somewhat careful of what are you doing. It is my understanding that the Solartron 7150W adds a pushbutton so you can switch between front and back inputs. There is also a Solartron 7150plus with better input impedance.


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HP 3456A & HP 3457A

HP3456A HP3457A

Top HP 3457A
Bottom HP 3456A

I am not dead yet, just very tired. This photo is just to show that something is happening on the DMM side of things.

As soon as possible, I want to write about linux-gpib, DMM and logging.


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HP 5300A/5302A

This basic counter came with a lot of equipment I purchased some time ago. I didn’t need another counter but I wasn’t going to complain of getting another piece of test equipment.

Anyway, when I turned it on it didn’t count anything.

The real counter is the upper unit (5300A) while the lower unit is the signal conditioning unit. The two units easily snap together (like the Model 3470 Measurement System) and so it is really easy to disassemble.

I took a look at the pcbs but there was nothing that seemed to be broken/burnt/missing.

I expected that it would have been fun to poke around the counter but it wasn’t meant to be as inside there is a slider switch with two positions: INT and EXT. On the EXT position, the counter expects a timebase on its read BNC connector while on the INT position we get the internal timebase on the BNC connector.

As you can guess, it was on the EXT position while it should have been on the INT position.

That’s it.



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HP/Compaq 2510p: changed DC power connector

I rather like my HP/Compaq 2510p so I have been really displeased when the laptop suddendly powered off even if it was attached to its power supply. The fact that I recently bought a new battery for it only added to my displeasure.

The first thing I checked was the power supply… which was dead. This sent me to a wild goose chase as I bought a new power supply which didn’t work, returned it, bought another one which worked but the laptop stubbornly refused to turn on.

Therefore I decided to dissect. On the HP site you can find the user and service manual so disassembling the laptop is not really easy but feasible (my keyboard was stuck in place and I had to apply more force that I would have liked to free it).

In the end, the DC power connector had a broken pin. I decided to buy a new one instead of just touching up the old power connector with a bit of solder.

As motherboards are cramped and the ground place is usually really good soldering on it is not the easiest thing to do but the old connector went out and the new connector took its place.

Now the 2510p works as it should.



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Merry Christmas 2018

Like I wrote in the title, Merry Chirstmas 2018.


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Anritsu MS610A repair (faulty 6dB pad)

This repair is my first foray into the almost-microwave realm.

So, what was wrong with this SA? I bought it unresponsive to the front keyboard commands.

After cleaning the contacts the unit started to be responsive, but the pushbuttons were rather stubborn against my attempts to clean them.

However, there was no response from any input signal if I hooked the cal signal from the back to the input. As I could see the LO feedthrough I was confident that the YTO was working as well as the IF section.

What appeared to be faulty was the input attenuator. Time to disassemble the RF section which wasn’t as simple as I would have liked: rigid coax and SMA connectors had to be dealt with as well as a lot of screws (and I’ve also lost a couple of them… I’ll buy them next time I do an order)

Inside the RF section after a 2GHz filter there is a 6db attenuator  which was obviously toasted: two resistor were burnt, and a capacitor followed them.

I am still not sure if the input attenator was faulty from the start or if I fried it testing the equipment.

Anyway, back to the repair. The service manual I found is not for the MS610A but for the MS610B and of course the schematic for the 6db attenuator is different from what was inside the RF section of my SA. However after a quick simulation I was convinced that some resistor and capacitor I had in my junkbox would be enought to test if the unit was working or not.

They did and I finally got a response from the SA when I hooked its cal signal. However the unit was not as sensible as it should have been and I couldn’t get the gain calibration right.

As the 6dB pad was fried I suspected that something happened to the first mixer too. There is no schematic for the first mixer, but looking at the PCB it looked like a double balanced mixer.

Unfortunately I wasn’t able to find any information about the 4 discrete diodes that made up the mixer: there was nothing about them in the parts list, no schematic, no marking that helped me identify them. It wouldn’t have been easy to find 4 matched diodes anyway.

I decided to try to substitute them with HSMS-282R, a SOT-363 package with 4 Schottky diodes inside in a quad ring configuration, exactly what I needed.

Desoldering the old diodes was easy, soldering the SOT-363 a little bit less easy. However, after reassembling the RF section, I got the spectrum I expected so at least replacing the 1st mixer was a success.

I cannot consider this repair complete because I am still not able to calibrate the SA with its own cal signal. Moreover, I should find the proper components for the 6db attenuator before going on with the repair.



I have misplaced four key caps and finally found them inside a toolbox. What was I thinking when I put them there?

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HP 6634A repair (blown filter capacitor) part 2

I finally remembered to order the three capacitors I needed for this repair in my last order and so I went ahead and did the repair.

To reach the main board I didn’t exactly follow the service manual: after opening the HP 6634A I just pulled out the transformer and then the main board. Done that it was easy: clean the pcb, solder in the three capacitors and then done.

I also calibrated the HP 6634A… it appears that someone calibrated it without setting up the proper connections on the back. Now it works as it should.


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