Power supply project: Input and filtering

Tracing out a schematic for this power supply has been pretty fun so far. It’s also been a good excuse to learn how to use KiCad.

So far I’ve made it past the rectifier and filtering capacitors up to the power transistors. I’m pretty impressed with the way the innards of this thing are put together. The bridge rectifier part took me a bit to figure out until I realized there were two different stud mount diodes in it.

Rectifier diodes
Rectifier diodes
Rectifier diodes
Rectifier diodes

I’ve come across a couple types of components that took me some searching to figure out what they were (still not quite sure what one of them is). This one in particular is one I haven’t been able to identify.

Mystery component. Diode? Transistor?
Mystery component. Diode? Transistor?

It’s connected to one of the outputs of the bridge rectifier and the control board at the top. At the bottom it’s connected to an air core inductor and parts that lead to the 2N5886 power transistors. A Google search of the numbers printed on it take me to a single page at a store that has it listed as a rectifier diode.

This is the schematic I’ve cobbled together so far. Things start to get a bit confusing after the rectifier, but I think it’s reasonably accurate.

Power supply schematic
Power supply schematic

I wasn’t able to find symbols for everything in the KiCad library, particularly for the connectors, so I just used something that looked reasonable.

This has been a fun exercise so far. The power transistor section will probably take me a while to figure out.

Power supply project

The dead power supply I picked up at the TARC swap meet last year has been sitting in a couple of closets for the past year, and now I’m finally getting around to poking around inside.

Power supply front panel
Power supply front panel

The innards of the power supply look pretty good. Everything looks pretty clean, no scorch marks, and hardly any dust.

Power supply innards
Power supply innards

Looking at the back panel doesn’t inspire much confidence though. Looks like at some point someone soldered a regular power cable to the original (I think) AC input and covered it with heat shrink. I might have to do something about that when I start working on the power supply.

Back panel AC in
Back panel AC in

So far everything looks in pretty good shape. Not sure what the problem with it is (aside from a blown fuse), but before I dive in and start mucking around, I’m going to see if I can reverse engineer a schematic for the power supply. There aren’t any labels on the power supply so I can’t look anything up. Should be a fun exercise.

Mystery component

At some point in the recent past, probably at a hamfest, I acquired these red square components.

Mystery component
Mystery component

I’m sure whoever I bought them from at the time told me what they were and that I thought they’d be something I could make use of. However, I neglected to label the bag with any information about them, probably because I figured I could find info about them online.

Silly me.

Fast forward to the future and I come across them again during another round of the “Organize the closet” game.

According to the printing on the components, they’re some kind of wide band transformer made by the Vari-L company. I’m guessing 9531 is the part number, and Z-Match is a model or branding for this part. No idea what the HF:112 might refer to.

They’re 0.5″ square by 0.25″ tall with 6 pins spaced 0.2″ apart (they fit nicely into a breadboard).

Mystery component pin numbering
Mystery component pin numbering

The numbering of the pins seems a little odd to me, but what do I know.

My Google-fu hasn’t yielded any useful results about the component itself, although I did find out the company was sued by the SEC in 2001 for financial reporting fraud and sold its assets to another company in 2002.

No idea how far back these parts date to, but considering the company history, it’s likely these little red squares are old enough that there won’t be much info online.

Using my multi-meter to probe the pins, I found that pins 1-3 and 2-4 are connected, while pins 5 and 6 don’t appear to be connected to anything. I guess my next step will be to put some kind of signal through and see what comes out the other end.

Update: Thanks to Thomas/LA3PNA for pointing me to a datasheet for the part (his Google-fu is strong). It turns out the 9531 is a date code (Week 31 of 1995) and HF:112 is the part number. Naturally, an obsolete part which Mouser shows as being manufactured by Qorvo, while the data sheet shows Sirenza Microdevices. The specs on the datasheet are consistent with the parts that I have. Thomas also suggests that they would probably be useful in an transceiver, so it’s doubly nice to know I have potential uses for them.

Another Si5351A board

A few days ago, Jason/NT7S announced the Etherkit Si5351A breakout board was getting an upgraded TCXO oscillator with improved performance. I’ve already got a few of them waiting for me to put to work, so why not add another one.

Unlike the previous boards I bought (from the crowdfunding campaign), the latest versions now come fully assembled except for the header pins. If the thought of soldering tiny surface mount devices was keeping you from trying the breakout board, worry no more.

The 10 mW WSPR beacon app note looks pretty interesting, and I think it would be fun to try to get one set up once we’re in the new house. I’d love to see how far it could be heard.

We’ll hopefully be in the new house in a few more weeks. I’m looking forward to getting the shack and workshop set up again so I can get to playing.

Si5351 on the oscilloscope

The Si5351 breakout boards all work, at least according to the frequency counter, so I thought I’d put the oscilloscope on one to see what was coming out. I just connected the output of the Si5351 board straight to the oscilloscope using an SMA/BNC pigtail. I’m sure it’s a totally incorrect way of doing it, but all I wanted to see was if I got a waveform and if it changed when I changed the Si5351 frequency.

I’ve been told that the Si5351 output is a square wave, and at kHz frequencies, that’s what I get. This is the 10 kHz waveform. Nice looking square waves.

Etherkit Si5351 10 kHz waveform on the oscilloscope
Etherkit Si5351 10 kHz waveform on the oscilloscope

Going up a few orders of magnitude to 1MHz, the shape of the waveform loses its squareness, most likely due to the way I’ve connected things (impedance mismatch, improper loading and all that). But, as the time base shows, it’s a much higher frequency signal.

1MHz wave form
1MHz wave form

At 10 MHz, there’s even more distortion of the waveform, but definitely higher frequency.

10MHz waveform
10MHz waveform

Up at 20MHz, things are looking pretty triangular.

20MHz wave form
20MHz wave form

So, TIL:

  • My Si5351 board really works! Yay!
  • You can’t just connect things willy-nilly to an oscilloscope and expect good results. (I already knew this, just wasn’t important for this purpose.)
  • There are still some things I need to learn about using this particular oscilloscope.