Hello all,
I'm a long-time admirer but a first time poster. I figured some would appreciate the research I did recently into the display section (specifically the CRT driver) of my Motorola R2014D Communications Analyzer. My original intent was to replace the (perfectly operational) CRT with an LCD, with the goal of reducing weight and power consumption.
For those unaware, the R2001 Series (A through D) are a series of RF test stations made by Motorola in the 1980s through the mid-1990s. The R2001 is the base model, which changes as options are added. Mine is an R2014 based on options, revision D.
My intent was to follow the below process:
1. Determine the beam control method used to paint the CRT display (raster scan, vector, VGA, etc.)
2. Buy or design a board to convert the determined signal to VGA 640x480 @60Hz
3. Buy a 5" LCD VGA display from eBay and come up with a bracket to hold it in the chassis
4. Get the LCD working externally in parallel with the CRT to judge accuracy / make circuit adjustments
5. Replace the CRT with the LCD, and remove the HV PSU section
First step was to see how the CRT was driven. Since the unit has many modes that are quite obviously run by a microcontroller, I proceeded under the assumption that this was most likely a raster-scanned CRT.
Consulting the service manual (fig. 3-2 & table 4-3) showed that the display board (A2) had the following test points of interest:
TP1: VERTICAL DRIVE
TP6: HORIZONTAL DRIVE
TP7: CRT Z-AXIS
On probing these TPs while the unit was powered on, I got the following measurements:
TP1: VERTICAL DRIVE
Waveform: Decreasing Sawtooth
Frequency: 60Hz
Vpp: 120V
TP6: HORIZONTAL DRIVE
Waveform: Increasing Sawtooth
Frequency: ~7.8kHz
Vpp: 90V
TP7: Z-AXIS
... definitely the Z-Axis
At this point, I thought I was golden. I was unable to find any raster-to-VGA boards commercially (surely someone has already solved this problem?) so I started thinking about a circuit design to convert this to the familiar VGA standard
http://tinyvga.com/vga-timing/640x480@60Hz. That is, until I figured I better check something else before getting elbows-deep into this project.
The unit has several modes. For those unfamiliar, the front panel looks like this:
The modes are:
- Gen/Mon
- Modulation
- Spec. An.
- Duplex Gen.
- RF Memory
- Signaling Sequence
- Freq. Counter
- DVM/DIST.
- Ext. Wattmeter
- IF
- Scope AC
- Scope DC
Many of these modes are digitally displayed, like above. Many of these modes, however, appear to the eye to be swept more like an analog oscilloscope, with a comparatively bright trace and no digital text to be seen on the screen. This had me worries about the display driving scheme, and I figured I had better check it out just to make sure it wasn't something other than raster scanning per above. Good thing I checked...
All of the modes are raster scanned except:
- Modulation
- Spectrum Analyzer (hybrid raster / vector)
- IF
- Scope AC
- Scope DC
These are all vector drawn instead of being raster drawn... so... to the best of my knowledge it will be nearly impossible to convert these signals to VGA.
Good thing my CRT is nice and bright...
Hope this helps someone. Thanks
P.S. For those of you who own one of these, and you have ever wondered what the display says when it is warming up, I connected the above TPs to my XY oscilloscope and got the POST screens for:
- SELF TEST
- TRUNKING SELF TEST
- SECURE COM SELF TEST
- SELF TEST COMPLETE
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