Tuesday, August 30, 2016

5LO38I CRT test

Having this CRT for some time, never tested it, so last weekend with the new soldering iron was the right time for it.

Honestly can't remember for which project I got it, in any case it will be useful in the future.. so I hope,

Power supply was based on this diagram:

From this site:

Added some discharge resistors so it unloads faster, even so it would take around 10m to go to 0v.

The brightness and focus control diagram:

From this reference:

Didn't used any circuit for testing the deflection but touching with a long wire is enough to cause deflection, so it's working also.

I might need to tune the controls and power supply since the dot is a little too big, don't know exactly what is the relation between focus voltage differential from the electron gun and the dot size, sure it's related.

The box it's standard soap box in plastic so I'm not tempted to touch the circuit while it's operating. If I finish the project it will be for sure placed in a more attractive enclosure.


Didn't had an isolation transformer 230/230 so used an 230/12 connect to a 15/230v. I had my shares of electric shock's and will no risk touching a rectified point directly to mains.

The controls:
The rectifier board:

upside down on the box so the electrons can drop easily...

And the connection to the CRT pins, this is the best way found since I had no holder for it, no mess with solder and quite isolated:

For reference, additional sites with more information case you want to build  a scope based on this CRT tube:


The technical details of the tube:

Have a nice day!

Sunday, August 21, 2016

Replacing the Maplin N78AR solder station Iron

One of the first things I bough when got to Ireland, three years ago, was a soldering station.

...Well it's not technically a solder station it's more of a soldering iron stand with some control on the iron power. Similar to a light bulb dim circuit.

In last few weeks the soldering tip was getting completely destroyed, normal after 3 years of intense soldering, I went to replace just to find out the retaining nut was completely stuck and in the process I broke the internal heating element.

Since there was no spare irons on sale for the station model, went online and spoted a vey similar one, tough less powerfull, 30w, the standard is 50w.
My guess it's the same manufacturer and then re-branded.

On the left is the new one... by this time I had removed the cable from the old one to prevent any accidental connection since internally the heating element wire was broken.

Replacing was just a matter of connecting the new soldering iron cables.

I reused the stress release rubber from the old cable
 The station has a retaining slot for the stress rubber, nice build touch.

Since I only have one working soldering iron could not solder the contacts of itself (I could but not safe to do), so they were very well wrapped and isolated.

The internal control circuit is a very simple one so no change was needed.

To open the "station", remove the 4 screws bellow the rubber feet.
Overall I find it well build. For the price and if you don't need anything fancy it can't go wrong.

Now I can go back to melt some solder.

Have a nice week!