The Paraset Breadboard Mk-I (or probably called in 60 years: The Velp MK-I)
Some photo's can be enlarged: watch for the little hand!

last update: 2010-03-08



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The production of my Paraset stagnated because of lack of the right old parts. As I could not wait to go on, I decided to build something so I could experiment with the Paraset schematics. It had to be a kind of breadboard, but rather universal, so it could be used for other set ups as well. During the process I discovered that some things could have been made different with a better result, that is why I named this set up a MK-I. The next one will be more universal and more versatile.

I decided to use a kind of printed circuit board as a base. But as I had not made a PCB for many years and I had no more chemicals to do so, I decided to use a technique that a good friend, Stef PA0PSI, had shown me, many years ago.
Stef showed me a little tool he used to make little insulated islands on the copper side of a non-etched piece of  PCB.

So I made the tool. It is a holder for a small centred drill bit and a small drill bit off- centre, that mills the island, so to speak.

To give you an idea how to make the tool, I made a drawing, that can be downloaded by following this link.

The measures in the drawing are just a guidance. Feel free to alter these.

Next thing to do, was to mill the islands on the copper side of the PCB. So I cut off a strip of a large PCB and made the three holes for the octal sockets.

I didn't make a proper plan but improvised carrying out this project. So things did not fit as well as I hoped for. Well, it will be better in MK-II.

I also milled "rails" for B+, earth and filament current. This was done quite easy by sliding the PCB along a guidance bar.


Than a way to hook up the controls had to be figured out. I decided to make a number of small, universal panels that could accommodate various controls. If later on different mounting holes for a certain control item are needed, the simple exchange of a panel will do, the rest of the panel(s) can be left alone.

I made 4 panels of equal size, bolted them together and drilled the holes in 1 action, through 4 layers of aluminium.

The whole of panels is mounted in a rectangle, made of aluminium angled profile. Because of the bad quality of the aluminium, that broke on bending, I had to solder the joints. Yes, one can solder aluminium, with a blow torch on 300 degrees, using a special soldering alloy.

In order to make the contraption a bit sturdy, I added a side panel, holding a Jones power plug, an RCA plug for LF out, and a jack for phones. The small hole in the centre was intended for a 3,5 mm mini jack, but that became obsolete.
This is how it looks, assembled. There is still white plastic cover on the panels. The back plane is made of plywood.

In the MK-II, the PCB will also be cut in modules, so modules using different tube sockets can be combined. Even pre-fab modules can be combined.

After a few hours of searching components and soldering, it looks like this.

It is an ideal platform to try out components and substitutes before putting them to the final Paraset. Soldering on the islands is easy, changes can be easily made, measuring is easy. Everybody should have such a contraption!

And the back side. Power supply and lf-chokes. The back panel is plywood, so you can screw on to that what is needed.
And than the RX-part is put to the test. A hell of a lot of noise came out the headphones! The Germans must have picked up that noise on a mile distance!

I can't let you hear it, but the modulation on the scope will tell you enough.

The frequency counter showed a tuning range from 3,053 MHz to 7,684 MHz. In the upper part were many AM radio stations to enjoy.

This gives a good feeling and one gets encouraged to go on.

The MK-II will have wider pcb-panels. It will be the same size as the front panels an contain one tube socket, each.