Pic-A-Star, the saga continues

Having decided to house the transceiver in the chassis frame of an old Tektronix  model 620 CRT monitor, and to use the Pic-N-Mix DDS unit as the control processor I needed to figure out how to fit that circuit into the confines of the frame.  I had obtained a bare board from Glenn, VK3PE, which had both the Pick-n-Mix and Status board circuitry on it, but the board was too wide to fit in the available space in the chassis frame, nor could it be cut into two pieces to do so.  So I ended up using Peter’s design as re-implemented by G6AK.

The Tektronix 620 monitor was a 6″ CRT XY monitor, the one I had no longer functioned and was deemed unrepairable due to critical parts no longer being available (at a reasonable price).  The chassis frame measured about 8″ wide by 5″ high and was about 17″ deep.  It consisted of machined front and rear panel frames mounted between 4 extruded aluminum rails.  The top, bottom, and side covers slid into slots in the rails.  My unit was an OEM model, which came without the covers, feet, or handle, and was intended to be built into the OEM’s product.  I had obtained the monitor from a former employer as dumpster salvage.  As the frame is deeper than I’ll need, I plan on cutting the four rails down, probably to a depth of between 12-15″, the actual length to be determined once I’ve built all of the necessary transceiver modules and test fit them into the available space.

PanelFront.JPGAfter removing the CRT bezel and the controls from the 620 front panel, I made a new panel insert to replace the bezel, and a dress plate for the control portion of the panel.  I wanted the various jacks and the audio gain control on the left hand side, so I’m using the 620 panel mounted upside down from the way it was originally built.  I etched the two PnM boards from the artwork by G6AK, and trimmed the boards down by about 3/4″ removed from the side where the home brew optical encoder was.  I’ll be using an available encoder unit from Oak-Grigsby.   The layout is a bit different from the way G3XJP intended it, I have the keypad and status board on the lower right hand side of the display instead of to the left of it, and the encoder knob underneath the display instead of to the right of it.  I’ve combined the functions of the four VFO indicator LEDs into two by using dual color LEDs, and I’ve added a dual color LED to indicate ‘Best IP3 mode’ and ‘Attenuator on’ functions in the place of one of the VFO LEDs.  The other vacated LED position will now be the DSP LED.  I had a large 12 segment, three color bar graph LED display in the junque box, it was mounted above the display and wired to the status board in place of the called for 1.8mm LEDs.  Since this display required more drive current than the PIC could probably handle, I added a small perf board containing 12 PN2222 transistors for the extra drivers.

PanelBack.JPGHere you can see the back side placement of the parts, minus the PnM boards.

PnMdisplay.JPGThe Pic-n-Mix display board designed by G6AK

PnMmain.JPGAnd the Pic-n-Mix processor board.
I added a second LM7805 regulator on the reverse side of the board, underneath the one on top to power the DDS circuit.  In this photo the LM7808 regulator for the Butler oscillator has not yet been installed, nor has the oscillator.  (The DIP IC’s also have yet to be socketed). I plan on using an On-Semi 340mhz LVPCEL oscillator to drive the DDS.  I got this part a few years back, it looks like it isn’t made anymore by On-Semi, but there are other similar parts still available in the same 5x7mm package.

These photos show work in progress, I still need to finish wiring up the front panel boards together, and then test/debug the Pic-n-Mix.

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