Inside a Tek 465

The TEK 465 'scope is as they'd say back in the Bronx "a piece of work."  It has real character.  Perhaps a bit too much.  If you look closely, you'll see transistors in sockets.   I had kind of gotten my head around that, when I noticed that many of the transistors were not in sockets.  They looked like they had been soldered to into the holes in the PC boards.  But NOOOOO!  They are snugly in the holes, but they are NOT soldered in!  You can pull them out, then (if you are lucky!) slide them back in.  There is even quite a bit of "ugly construction." with connections floating in the air.  You can really see the influence of tube era thinking in this instrument.

I think I have narrowed the problem down to the HV supply.  Alan Wolke is lending me a high voltage probe.  I hope to be able to get it fixed this weekend.  I need to get it working because my BITX 17 is nearing completion and I'll need the 'scope for the lineup and de-bugging.

The picture above is from:  http://www.eevblog.com/forum/projects/tektronix-465-repair-and-restoration/   More pictures of the scope are available there.  Also see http://www.spurtikus.de/basteln/repair/tek465/index.html for more scenic views of this instrument.


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Battushig has The Knack (Mongolia and the MOOCs)

"How does a student from a country in which a third of the population is nomadic, living in round white felt tents called gers on the vast steppe, ace an M.I.T. course even though nothing like this is typically taught in Mongolian schools?"

"Most homes in Ulan Bator have Internet connections, and almost everyone, including nomads, has at least one cellphone. Even on the steppe, with only sheep in sight, you can get a signal."

http://www.nytimes.com/2013/09/15/magazine/the-boy-genius-of-ulan-bator.html?pagewanted=all&_r=0

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update # 7

As you can see (above) I've made lots of progress on the BITX-17.  Going counter-clockwise from the lower right, you can see the mic amp, the BFO/carrier oscillator, the first mixer, the first and second bi-directional amplifiers, the diode ring VXO mixer and the VXO.

I plan on building the whole rig (including the power amplifier stages) on this wonderful piece of PC board (thanks to Jim, W8NSA).

I had what I thought was the brilliant idea of using LEDs for  all the T/R switching diodes.  I thought I'd use red for receive and blue for transmit.  I consulted with the BITX yahoo group and cooler heads prevailed.

The design has an LM-386 as the speaker amp.  I'm kind of bothered by this -- I'd prefer an all-discrete component rig, so I am thinking of building an AF amp with discrete transistors instead, perhaps the circuit from Roger Hayward's RX for the Ugly Weekender.  What do you all think about this? 

I'm having a lot of fun building this rig.  If anyone out there is looking for a fall/winter project, build one of these.

I have to order some 5 MHz crystals for the filter and oscillator.  Mouser has them at about 70 cents each.   


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #6: Rock Steady

So, having given up on the VFO,  this week I built a VXO.  The IF in my W4OP-built Barbones Superhet is at 5 MHz.   That receiver has a VXO running at 23.133-23.168 MHz with two crystals switchable from the front panel.  My plan is to build a 5 MHz filter for the BITX 17.  So I just plucked one of the crystals in the Barebones RX and used it to test and tweak the VXO.  Trying different values for the series inductor, I got wide variations in freq swing.  With .7uH I could only pull the rock 9 kHz (too little).  With 5.6 uH, it was pulling 434 KHz (way too much -- it was acting like a VFO). 3.213 uH was just right:  With my 19-148 pF variable cap (with 53pF in series) I got a swing of 22 kHz, with crystal-oscillator stability.

I know, I know:  I could have done this with a DDS chip, or with an SI570.  But simplicity is a virtue, and the BITX is all about simplicity, right?  Having recently built a DDS RF generator, and now this simple three transistor device, I must say that I like the simple analog circuit better.   But hey, that's just me.  I'll talk about this in the next podcast.

Today I built the mic amp circuit.  You can see it off to the right of the VXO.

One of these days I'm going to have to actually troubleshoot and fix my Tek 465.  But I'm
afraid of that thing!  The voltages in there are HIGH, and so is the circuit complexity.  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Moon Launch from Virginia (video)

NASA launched a mission to the moon last night.  The rocket went out of Wallops Island, Virginia and was visible from Washington D.C.   I forgot about it, so we missed seeing it ourselves, but this fellow got a nice view from the balcony of his Washington apartment. 


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Burning Man: Probably more Fun than a Hamfest!

Check out this report from the Burning Man event.  Two intrepid nerds head out to the dessert  (with ham radio gear) and appear to have an amazing time. 

http://blog.thelifeofkenneth.com/2013/09/my-first-burn.html


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

NASA needs Ham Help! Say HI to Juno (on its way to Jupiter) on 10 meter CW!

This is really interesting:

http://www.jpl.nasa.gov/hijuno/

Thanks to Richard, KK4JDO, for the heads-up.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20