2023. szeptember 16., szombat

Building my rack(s)

In my previous lab, I had a small (27U) rolling rack at the side of my desk. When it finally got its shape, I started to move to my new lab. The equipment removed the rack disassembled.

I was a bit depressed on this as I had the feeling I'll never be able to put this together once again.
As I was reading things on the Facebook, I seen a guy trying to sell a whole bunch of outdated Cisco networking equipment. Nobody was interested, there came ugly comments on it, to throw the whole thing to the trash.
I seen a potential on something. Those Cisco units were installed into rack. So I wrote to him, if the rack containing the switches are on sale.
So I've two Rittal 42U height 600x800 racks for $100 each. I had some cleaning, metal work and paint repair with it (full repaint wasn't required, it has almost no rust just some dirt). One set of the vertical rails are not compatible, one rail mount was missing. Also I wanted open frame rack, so removed all of the doors, side panels, back panels.
Also I wanted to be able to move it on some rollers, but not every direction, just strictly need to pull out from the wall to be able to access the back. So I made legs with bearings as rollers.
In the last week finally put back most of the equipment to it (some not fit, it will be go into the other rack when I'll able to find time to rebuild the back vertical rails.

One of my problems with the rack, how to access the equipment connectors on the back, from the front of the rack. I wanted something modular to be able to put various type of connectors to it.
Built a 1,5U unit onto the top of the previous rack from aluminum extrusion a 3D print. It failed. Wasn't precise enough, won't fit things I wanted to put in.
I was thinking about some Panduit modular patch panels, but never bought it. So just left it.
I put this thing to a side for years.
When I started to build my new rack a few month ago, I just seen something interesting on the net. Asked the owner, what he was using. It turned out, It is a Middle Atlantic Products UCP series modular kit: https://www.legrandav.com/products/accessories/connector_panels/ucp_hinged_frame_kit/ucp-sf
It has two issues for me: It is not on sale in Europe, it uses imperial screws what isn't easy to source here.
I designed and built a 3D printed 3U height modular front panel. It can accommodate 16 modules. It is great, I put it into the rack already, with the breakouts of the four channel HP 6627A power supply.

This could be the final solution, but...
...when it was already built just realized, there exists something called Eurorack Modular Synths. It perfectly match with my ideas. I bought two set of rails.

The 19" rack mount was not included, but by surprise, the original endpieces are already 3D printed

The plan is to design a new endpiece with rack ears.
In the first rack, I'll keep my original design, but in the further rack or racks I'll switch to EuroRack.
In the last few years I was mainly working with Kubernetes. For this I previously built a K3S cluster from 5 Pine A64 SBCs. It broke down (dead SD cards), but I intend to rebuild it.
I thought, it would be a great idea to put these units into the modular front panel. Designed a holder for it.

Didn't print it when the design was ready as my printer had issues, later I didn't find time for it.

To be honest, I done not too much in my electronics project during the summer. The PCBWay asked, if I have problems - absolutely not - and suggested why I don't try out their 3D printing and CNC machining capability.

I was thinking this is a perfect opportunity for this. Made a quotation to this in PETG and some small part in resin. I can tell you, I was shocked. Mainly in the resin prices.
If the things I'm trying to print with a resin printer coming on these prices, absolutely nothing justify keeping my resin printer in the future.
Now the quotation is on. I'll write about the experience and my further way in 3D printing when the printed parts arrive into my hands for inspection.

2023. szeptember 5., kedd

Fluke 787 "Repair"

Big thank you for DuraLeak.

"i purchased this at an estate sale.  i don't know if it works or how to turn it on.  but as it is right now i have pushed every button and nothing comes on the screen.  so because of that i am selling it for parts or repair."

Perfectly working Fluke 787 Processmeter for $143 delivered to Hungary

I need some future tests, but looks ok, for the first sight.

2023. augusztus 27., vasárnap

Dumpster Dive - "woodwork"

A few days ago, I found this nice table frame next to the dumpster.

From the paper box next to it I seen some broken glass, so I suspect it was a glass table before, but the tabletop broken. The owner just thrown it away. Actually it has no issues other than the missing top.
Yesterday I went around the city for some shopping.
Find a 120x70 LDF (not that shitty paper filled crap they mainly sell nowadays) tabletop in the IKEA (it is exactly 15cm larger than the frame in every direction) and bought some aluminum L extrusion in the Bauhaus.
Todays work:

Ooops, a scratch I made while putting it onto the tabletop

I found the function it also - Resin 3D printing and ultrasound cleaning station

Also accommodate some chemicals

and the 3D printer spare parts

Excess paint

And even some free space also left

2023. augusztus 22., kedd


There is some (re)addition to my hobbies.

A few years ago (mainly at the film based era), I was seriously involved in the amateur photography. Went nowhere without an SLR camera. A few years ago, this swept away a bit. There are many reason behind it. I guess the main reason was the better and better cameras in the smart phones.

Anyway, I was never completely satisfied with the performance of it. It was good for documenting my electronics projects but... It was good for my daily needs but...

Then the COVID came. It bring with it a closing down the things. Working in IT with cloud technologies bring almost zero need to go to into an office. My main hobby (still will be) electronics is connected to my lab, what is a closed space. Actually days passed by without going out to the street.

It looks like two and a half year was the limit to me to be able to tolerate this kind of lifestyle. Enough.

So a few weeks ago, I took out my photo equipment from the locker and started to use it. With it, go out to the city, to countryside, just for taking pictures. I love this feeling.

I also plan to move from phone to this equipment also for other photo/video related activities. For this plan, I started to upgrade my set a bit. It doesn't mean buying new equipment. Much more started to collect 2nd hand tools. Added an FX camera (Nikon D610) to be able to utilize the lenses from my film era. Added macro lenses for my object photography goals.

The current set:

My new photography journey starts here.

2023. június 28., szerda

Keithley 2700 - Repair 2.

After some serious issues with the local post, Today the new mains transformer of the 2700 landed in my hands.

So I measured a bit, then installed into the unit.

Actually it was pretty straightforward. Everything connected, assembled.
After some warmup I compared with my 7.5 digit Keithley 2010. It looks like spot on (the Digistant source not really able to keep with them).

2023. június 13., kedd

2023. június 12., hétfő

Reference Resistors

A friend of mine asked me for a quick project (finally it become not so quick, but just because the time it required the parts to arrive).

He is installing pool and other water handling related systems. One of the pool measure system has PT100 temperature sensor input what need calibration. The proper calibration equipment cost a fortune. Actually he only need two reference point. For this he asked me to make some reference resistors in a box what is precise enough and has low tempco.

The values are 100 ohms and 119.4 ohms what is weird a bit. Looked around and find the required resistors in 0603 and 0805 size (100 and 120 ohms 0.01% 2ppm) around $10 each. For the 119.4 ohms I planned 24k in parallel with the 120 ohms (bit less precision as there is not needed better).

I bought some tiny aluminum boxes from the AliExpress. The idea to change the front plate of the boxes to a PCB add the screw-in banana sockets and put the resistors to the back of the boards.

It looks like this:

It was manufactured by PCBWay in the usual excellent quality - Thank you!

I was a bit afraid, if they can follow my request and put the order number to the already crowded component side, but it was managed without problem. It arrived together with my VFD project board, what I'll write about later.

The board soldered (Yes, it is a joke. Only one single resistor in this case)

Some measurements

If I count the cable and the plugs contact resistance is the result get even better. I'm satisfied with the result.

And the final boxes (the request was about two units.

I put two resistance values into a single box. The only thing left is to print some labels on it with the values.

Spectrum Analyzer

It is itching. Yes, you can tell: scratch it.
Actually I'm in a debate with myself. As I read more, more confused.
I need a Spectrum Analyzer. Or maybe not. Yes, I had an HP ESA, but sold it. It was a 75 ohm model with a frequency range doesn't go below 1Mhz, what is I felt is a no go for me. Yes you can tell that those things can be handled, but it is too late. It is gone, so look into the future.
What I need an SA for
  • Audio measurements. I need to cover let say from 10Hz to 100kHz. Yes, this is wider than the audio range, but it is good to know, what the electronics do outside it.
  • SMPS measurements. I'd like to characterize the noise of the things I buy or build, get EMI probes, etc. No, I don't need it for FCC or similar acceptance, just to know, what I bought it a quality unit, or a heap of crap. I guess the frequency range is from 20kHz to a few MHz. Also I intend to find out, the ideal frequency of unknown SMPS transformers. I guess later also need a tracking generator.
  • Characterize frequency references. Lately I was playing with rubidium standard, I have also a few OCXOs in my parts box, for later use. Intend to build a GPSDO or similar unit. Those things are running around 10MHz
  • Repair characterize maybe calibrate AM/FM generators. It happened to fall four Panasonic/Levar VP-8193A/D onto my bench. All of them has issues in the RF section (looks like the control part works perfectly, the LF part I didn't check yet). For repairing, later calibrating it. For those I need a frequency range from around 100kHz to around 200MHz. It also need analog modulation analysis for AM and FM.
  • Sub GHz and GHz digital communication. It is in my mind to play with 433kHz, 868kHz, ZigBee, Z-Wave, LoRa, Bluetooth and WI-Fi. The sub GHz can be handled by most of the analyzers but the 2.4GHz is a different story. Also those things are requiring some kind of Digital Modulation Analysis, what not all of the SA has.
What test equipment or similar have I currently
  • Hack-RF SDR https://greatscottgadgets.com/hackrf/one/. It is by design is not a test equipment. I need to figure out, get some advise, if I can use it for any of the functions above. It maybe good as SA, AMA, DMA for the RF range, but has no idea what can be achieved with it or even good enough for measurements. Didn't use it up to know just have it in the drawer for a while.
  • Boonton 8201 Modulation Analyzer. Probably good for the AMA function (if it works, not yet tested)
  • Rigol MSO-5074 (with all of the options added, so it is a highly capable 4 Ch, 350MHz, 8Gsps oscilloscope). I think the FFT function can be good for some of the low frequency measurements, but I'm afraid of the ADCs 8bit resolution for this kind of sensitivity required work.
  • HP 35665A Dynamic Signal Analyzer. Probably good for most of the audio related work together with the other audio equipment I have
  • Steinberg UR22 mkII external sound card. Plan to use for audio. There are quite capable software available for free online, I also have a measurement microphone, power amplifier, Dayton DATS v2 to extend the capabilities of the computer based measurements.
  • HP 8903B Audio Analyzer. This is a highly capable unit, but unfortunately I can't count on it currently as it need repairs/calibration. The linearity in the frequency range is a way off even just connected its generator output, to its input
  • Keithley 2015 THD multimeter. It is able to commence some of the functions of the 8903B.
What options I have
Actually I targeted the budget max €1500+VAT.
  1. Doesn't buy anything just try to utilize my current equipment for the purpose above. It may work, but deffinetely need some advise, starting points for information.
  2. TinySA Ultra. It is probably able to fulfill most of my RF needs. I just not yet know if it has drawbacks other than the small display. Some more research will be needed.
  3. Owon XSA-1015P-TG. It seams to be a great unit. I checked this video: 

    It looks like, on most of the parameters it is better than the Rigol (I was considering previously, but based on my research I dropped it already). For €975 it is a great deal https://eleshop.eu/owon-xsa1015-tg.html.
  4. Siglent SSA3021X-Plus. This is a similar unit as the previous Owon, but it cost a bit more €1469 https://eleshop.eu/siglent-ssa3021x-plus-spectrum-analyzer.html.

    It has upgradability to 3.2GHz (covering the Wi-Fi and Bluetooth band), has AMA and DMA option. I didn't see any of those in the Owon specification.
    But still, there are some things I miss in both of the units:
    1. Not covering the audio band
    2. The TG minimum frequency on both units starts at 100kHz, what is too high for testing SMPS parts.
  5. Signal Hound SA44B Spectrum Analyzer + TG44A Tracking Generator. Those units together are bit above the budget what I willing to spend ($1930 together) https://signalhound.com/products/4-4-ghz-scalar-network-analyzer/
    It looks like resolve my low frequency questions as it start at 10Hz (both the SA and TG).
    I'm a bit afraid being solely PC based USB device, and not yet sure if all of the functions are available I'd like to have. Actually I found a review video on it.

    I not yet watched it as it is two hours long. I should find the time before I decide.
So, here I stand today. Bit more confused than a few days ago, when I started to look.
If you have any ideas, thoughts on this, please let me know. I really would like to get some hints on this. 

2023. május 29., hétfő

Keithley 2700 - Repair

 I couldn't resist. Found this puppy faulty on the eBay.

It doesn't turn on. Even consume zero current from the mains.

For a quick look: the fuse is intact. Tested the AC connections from the mains transformer. Nothing come out. Ok, so either the mains transformer or the mains connector module (connector, voltage selector, mains switch) faulty.

Checked the Mains connector module. Unfortunately the available service manual is useless. So with the mains module, done some reverse engineering.

Here is the transformer's connection:

Measuring the transformer I found out, that the 100V winding is demaged.

So, I connected the 100V - 220V cables (blue and gray) to my variac, and set the voltage to 120V.

Here are the results:

For the first sight, it looks like, it has no other issue than the faulty mains transformer. Now I need to find a replacement unit, or somebody, who is able to wind a new one for me.

2023. május 22., hétfő

Analog Multimeter 3. - PCBWay Review

My boards arrived Yesterday from PCBWay.

As this is the first time I use them as board house I'd like to write a small review here.

I'm ordering PCBs from various manufacturers in the last 14 years. I started with some local manufactures. Those guys had horrible prices and not so good quality (anything above the single side board had additional cost, etc.)

10 years ago I changed to the board houses located in China. As my projects mostly has no time constraints, the long delivery time hadn't be an issue to me.

There were a certain PCB size what manufactured on the low cost ($5 + shipping). This started with 50x50mm, then become 70x70 and lately 100x100. Almost all of the manufacturers today provide 10pcs 100x100mm two sided, masked, silkscreen printed boards for 5$ + shipping.

This is where we stand today.

Lets check the order process of PCBWay. I had a simple 100x50mm board, for prototyping my SuperTracking regulator (based on Walt Jung/Jan Didden design).

It is a great thing to have a gerber viewer and automatic size calculator in your order process. Here the PCBWay site tricked me a bit. I didn't find this feature on the first sight. It is not reside on the main ordering page you see at first. You need to switch to the "Quick-order PCB" page to get this.

I absolutely love this feature:

It means you order your PCB with HASL (tinned) finish and if you are lucky you get ENIG (gold plated) finish. To understand, the manufacturers put your hobby projects into the big orders process. If you tick this checkbox, you may get a gold finish. The manufacturer on the other side has greater flexibility where they put your order. This is an absolutely win-win situation.

We care about the environment. The EU doesn't allow lead based solders for a while in the consumer electronics devices. At the board houses, you can select between the leaded and the lead free finish. The manufacturers I seen previously charge extra for the lead free finish. This come from PCBWay with no additional cost.

If you ordered already PCBs, you always find a tiny order number on your board somewhere. In most of the cases this doesn't cause any problems. You have the paying option to remove this number. This is not always necessary. Check my previous design, what is the scale of the meter under design. There could be a problem to see this number on the visible area of the board. Here you can add special request written where you want to place this number. At other sites I seen a method, you can add a specially formatted text to your silkscreen where the manufacturer can put this number. I feel this point as room for improvement.

At PCBWay you pay your order after the review (in few hours - it took me a day, probably because I ordered my board during the weekend). Other manufacturers require the payment upfront. I think it is matter of taste. I prefer this method. It give me some time to review myself if everything is ok, I didn't make a mistake at the order (unfortunately paying upfront caused me trouble in the past).

One additional thing about the order process. Providing and stating to provide IOSS (Import One-Stop Shop) is a help for the EU customers from two point: the order arrive faster and you don't need to do the paperwork at the local customs or tax authorities.

The order of mine arrived on Monday.

The quality of the boards are excellent. Didn't find any issue with it. This is the quality I expect from the boards I want to use.

I was eager to populate it as soon it arrived. I was sure that all of the required components arrived. Jumped into the build. Immediately realized that three parts are missing.

One is the voltage reference I intend to use. It is my fault, forget to order it.

The other two is the dual OpAmp and the small NPN transistor. I got a message from Mouser: "Shipments of this product must be direct to an END CUSTOMER from an AUTHORIZED DISTRIBUTOR only.  Your customer must order this product directly from Mouser or another authorized distributor."
Come on! I never sold components as a reseller. I'm just an engineer who time-to-time fix things, design equipment.

Contacted Mouser, It took around three days to settle this.

So yesterday finally ordered the remaining components. Waiting for the arrival.

2023. május 10., szerda

VFD Mania 3. - Reverse engineering, filament supply

In the last few years I collected many VFD tubes. In the last weeks, a bit cleaned it up, unsoldered a few to have just bare tubes.

This is not all, but most of it what I currently have.
I wanted to make a catalog for myself with the pinouts. On the internet there is no common source of these. No datasheets, etc.
So the reverse engineering is required. For this I built a small, simple device (it took less than an hour from the idea).
For testing I need a 2.5V as a filament supply (may not the ideal solution, but good enough for testing), and something (12V good enough), for the anode and gate.
So, I built this:

The two blue banana can be connected to the filament pins, the two red sockets for the gate and anode. With this I can quickly find the segments.
Currently documenting it to a simple Excel sheet, but looking for a better solution, to able to publish it.
Finally took the time to test the previously designed/built filament supply.

It started to work immediately, but...

The waveform is horrible.
Superposed to the -27V supply is not much better:

My first hint was instability at the last inverter (but it was highly unlikely). Testing, the previous circuit state generated this:

I got a hint from a group (I would try it myself anyway), to check the supply voltage.
It looks like, the 20cm cable I used has too much resistance.
Adding a 1000uF capacitor to the input voltage of the module produced this:

Still has some overshoot, but I think, I'll be able to handle this at the final design.
Next, I'll order the complete PCB for the Futaba 15MT67GNK and the Princeton controller IC.