From: uhclemLOSE.apr09@nemesis.lonestar.org   
      
   Tim Gilchrist  wrote:   
   : Hi All,   
   :   
   : I'm a Tandy newbie, so apologies in advance for anything   
   : obvious/wrong/silly :)   
   :   
   : I rescued a Model 4 from the kerbside a while ago which has a video fault.   
   :   
   : Essentially, the beam appears to be always on. Every scanline is drawn,   
   : as is the retrace. There doesn't appear to be any variation in the   
   : brightness, other than the retrace being a little dimmer (which makes   
   : sense, I suppose).   
   :   
   : If there are any TRS-80 hardware gurus out there who might identify it   
   : as a common/known (fixable) issue for this hardware, I'd be very   
   : happy... I'm not confident enough poking around near HV circutry to do   
   : any live troubleshooting myself.   
   :   
   : If anyone is keen to help, I can supply pictures.   
   :   
   : If noone is able to help but would be interested in providing a loving   
   : home for it, let me know. I'm in Western Australia though, so postage   
   : may be expensive if you're somewhere else :)   
      
      
   First, try adjusting the brightness and contrast knobs located under   
   the very left edge of the case near the power switch.  The machine   
   may simply have the brightness knob turned up too high and the   
   contrast knob set too low, which will cause the display symptoms   
   you describe.  Plenty of units were brought into repair centers back   
   then with the same "problem", and may not have even known those   
   two knobs were there.   
      
   With the computer on, hold down the BREAK key while pressing and   
   releasing the orange button (the RESET button).  This should get some   
   text up on the screen to work with even without diskettes.   
   Pressing ENTER after that point will put you in ROM BASIC and you   
   can get more text on the screen.   
      
   If the problem is more than that, I would check the cable between analog   
   video card (in top of case) and CPU board (in bottom of case) to make   
   sure it hasn't popped loose during rough handling.  If you have a   
   raster, the analog video board is obviously working.   Take care when   
   opening the case and removing the cover.  Many a novice has broken   
   the neck off the CRT when doing this seemingly simple step for the   
   first time, as there are a number of things that can catch the neck   
   of the CRT, the socket or the wires leading to it while removing or   
   installing the cover.  The Model III/4/4D/4P are definitely built more   
   like a CRT television than a computer in this respect.   You can   
   monitor your progress by looking through the hole for the upper   
   diskette drive (if there is one), to see if anything is coming   
   close to hitting or catching on the CRT neck while lifting the   
   cover mostly straight up, then lay the cover on the left side   
   (as you face the keyboard) of the computer.   
      
      
   Frank Durda IV - send mail to this address and remove the "LOSE":   
       http://nemesis.lonestar.org   
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      "A what?"  "LETNi! LETNi! LETNi!" - 1983   
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