Data General Dasher 6053 Terminal

Data General Dasher 6053 Terminal

General Info
Manufacturer	Data General
Device Category	Terminal
Identifiers
Model Number	6053
Power Requirements
Power Connector	IEC C13/C14 Socket
QR Code
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The Dasher 6053 is an RS-232 serial terminal for the Nova computers. It has an internal card backplane that houses all logic for how it works.

The CRT is a drop in Motorola M3000 Monitor (archived) that is a separate module.

Repairs - Modifications

2025-02

• Reformed three main DC PSU caps

2025-03

• Analog issues with CRT started
  • Symptoms observed before opening unit
    • First the black level of the CRT would start slowly raising. Turning the brightness knob down would cause it to "reset" sometimes for hours.

    • 

      Gif of black level raising and being reset by brightness knob

      • Unconfirmed, the brightness raising without being reset caused a raster collapse that results in a loss of video. The loss of video would persist unless the unit was left unpowered overnight
    • Raster collapses temporarily after adjusting brightness knob up
    • Video beam is not visible after raster has collapsed
• After a loss of video beam before I wanted to work with the terminal I decided to begin maintenance on the CRT
  • Changes and Notable Measurements
    • Replaced all small electrolytic capacitors as part of diagnostics for CRT issue
      • Every small electrolytic capacitor measured extremely high ESR
    • Checked multi-element capacitor and it measured good on both elements
    • Checked several foil polymer capacitors as good
    • Tuned 70V DC power supply on CRT from ~72VDC to ~70.05VDC to be more in line with Motorola M3000 manual
  • Symptoms observed after opening unit
    • During temporary raster collapse the 70VDC rail is pulled low
      • The AC input to the 70VDC power supply is also pulled low
      • No increase in current was observed on 70VDC rail before raster collapse, it was consistently around 364mA.
    • At least once on power up a static/arcing sound was heard around the flyback and the raster did not start
      • Flyback anode cable is visually concerning
    • Multiple cracked solder joints on both of the PCBs on the M3000
• 
• 
• 

• • • After some work resoldering pads the display eventually came back but has a horizontal sync problem. This is potentially related to the new electrolytic capacitors.

      • 

        The horizontal sync frequency was measured on R64 to be approximately 16.7kHz when this photo was taken. The image is not displaying correctly.

      • Adjusted L50 on CRT Horizontal PCB to bring internal H-Sync frequency to 15,750Hz, this brought the phase lock loop close enough to the input sync rate to lock on and the display now works!

Cards

Card Number	Card Type	Schematic	Card Photos
107 000765 01	Display Video	001-000942-07 Video Timing Generator (archived) 001-001187-00 Option Character Generator (archived) 001-001322-01 Option Terminal Enhancement (archived)	Left Full Image Right Full Image
107 000595 04	Display Memory	001-000943-05 Display Memory (archived) 001-001033-01 Option Terminal Enhancement (archived)	Left Full Image Right Full Image
107 000598 02	Display Control	001-000944-00 Display Control Decoders Cursor Logic (archived)	Left Full Image Right Full Image
107 000596 02	Async Interface	001-000941-05 Asynchronous Interface (archived)	Left Full Image Right Full Image

Schematic for Motorola M3000 CRT

External links

• Motorola M3000 Monitor Service manual (archived)