Sunday, January 31, 2016

Magic eye 6E2 tube/valve kit

Since I really like tubes/valves, bulb's, crt's, led's and similar light/electron emitting devices and looking for sometime to experiment with magic eyes, finally spotted one in kit form and within budged! After a month it arrived and costed less than 6 Eur, shipping included...

It arrived well packed along with the local bank publicity... I suppose...

The tube was a little dirty on the glass, my guess, it was made to be cheap and not to be beautiful like we see on some other tubes.

Connected the wires and started testing the heather, since this, besides the glass envelope, is the most fragile was in good shape and didn't burned during power on! So far so good!

Now the plates power under normal light conditions, it worked! First time!

All the glory under low illumination:

Power supply using a 230 to 12 and 12 to 230-0-230 transformers as isolation, I had my share of electric shocks so I like to avoid them whenever possible:

A simple 7805 is providing the heater voltage.

And the schematic:

I didn't tried yet to bias with low voltage on the diode to see if would be simple to transform the circuit in a s-meter indicator from an agc voltage...

Have a nice week!

Sunday, January 24, 2016

Light house bulb

Got this bulb around 1991/92, when a local book store went out of business,
 I was bought along with a simple book on electronic/light sensitive devices and other I can't remember. Since it was on sale, the price if I remember correctly was something like 100 Portuguese "Escudos" (or less), that is now a days 0.5 Eur, priceless! I just can't find the correct reference, in any case, it's an Osram brand 220V 300W

According to the store owner it was the lamp sold as spare for one of the city lighthouses. Peniche has a main light house, two at the harbor entrance and a small pilot light on the north side. The lamp is "only" 300 Watt's, so I suspect being true the story, it would be for the small pilot light marke "L Fl R 7s" on the map. Translated from "nautical": Long Flash Red with 7s off period:

The last time I power it on was when mains was still 220 V, now with 234 V and the age of the lamp don't know if will risk it again (maybe in series with another lamp). I couldn't find the matching ceramic bulb holder, I know I have it somewhere....

Look at he size against the Hameg scope.:

And the Sailor receiver:

Still didn't found a good use for it but I really like the unusual size!

Have a nice week!

Sunday, January 17, 2016

Trimble OCXO 65256

Got this unit some time ago during a search on a popular bid site, it's a 10Mhz OCXO (oven controlled crystal oscillator):

Do I need one, NO, in any case it would be good to have one case needed. The idea is to zero beat it against a well know reference source (either GPS or WWV - and then use it as reference for a frequency counter.

After initial power on, this was the waveform on the output:

Don't know how precise is the scope or the real frequency on power on without a control loop, so at least looks around 600Hz difference between the two equipment's. Open circuit output Vpp is 300mV.

Model/Part Number is Trimble 65256 , there's also a reference TPN 57964-05 (Trimble Part/Number ?) my guess this will be the main board or secondary reference.  I've found no datasheet on the module so went for the 5V recommended  by the seller for power supply (se my previous post on running two LM7805 to power the "beast"). I didn't measured the current consumption, my guess is that will be close to 1A, at least for initial heating.
I've seen other similar modules (not the exact reference) running on 12V, thinking back, that might be a better idea,

Temporary power supply diagram using two LM7805:

The pin-out and size compare against a standard 9V battery:

Still need to implement the control circuit using VREF and VFC, for now it's free running.

Have a nice week!

More current from 78xx regulators

Yesterday I needed a little more current from a LM7805 series regulator. This was because I had no heat sink available and it was going in thermal shutdown without giving me time to test the application (more on this application on a future post).

I looked for a 2n3055 or 2n2955 to extend the output current, had none! Bad luck! (that I could find anyhow)

Thinking a little bit, I tough in paralleling, found some circuits which didn't appeal to me, so resorted to the datasheet to find the best way.
By the way, used this document for reference:

Here' the resulting circuit (with my adaptation):

I didn't placed the caps, was just a quick test. The resulting quick deployment:

Diodes were 1N4007 but any of one from the 4000 series will do.
It worked fine, anyhow I should place 3 instead of 2 since their still getting hot to fast (heath sink's are on my to do shopping list!..), well it gave me time to test and that is enough.

Another possibility if a 2N3055 or 2N2955 is available (circuit is for 2955):

Have a nice day!