2016-09-21 22:27 GMT+02:00 Pete Lancashire <p...@petelancashire.com>:
> They look pretty bright to me for a DVST screen. Your problem looks > 'analog', check the character blanking is working, then check the digital > to analog, deflection etc. > I also think it is a analog problem. But since I don't understand how it works I cannot pin point where. There are two potentiometers (conveniently located underside the machine...) that controls the character intensity timer and cursor intensity timer. "Intensity timer": how is that supposed to work? I don't think the Char Gen ROM is bad. I have seen perfectly drawn characters. The deflection probably works to since I was able to fill the entire screen with garbage. Timing problem. Yes. Since it often enable the beam when just starting to deflecting it I think that there is some analog timing circuitry that doesn't behave well. This gives the effect of some lines are drawn from the center of the screen. I should have made a short video since it probably give a better idea what is going on. > > When you hit the erase what happens ? > It erases the screen as expected. /Mattis > > -pete > > On Wed, Sep 21, 2016 at 12:07 PM, Mattis Lind <mattisl...@gmail.com> > wrote: > > > I took a look at the Tektronix 4051 that we got a few years back. After > > checking the PSU I turned it on and it seemed to start up fine. The > machine > > responded well to the keypresses but it was hardly readable on the > screen. > > > > Anyone that can give advice on what is wrong and how to deal with it. The > > text on the screen is very faint and many characters are scrambled as if > > the beam was moving when the points where plotted. When typing there is a > > flash of the beam which is then stored as the scrambled text. > > > > http://i.imgur.com/iQhQW67.jpg > > > > It probably reads "SYNTAX ERROR" something on the screen. > > > > My experience with DVST device is minimal. I used an old Philips storage > > oscilloscope many years ago but I don't remember the screen to be this > > dull. > > > > It seems like the storage system is not at full output. Unfortunately I > am > > not getting a good understanding on how the DVST system works from > reading > > the service manual. What is the purpose of the timers for cursor and > > character intensity? > > > > I am about to check all the voltages related to the display mentioned in > > the calibration section of the manual, but just in case someone directly > > recognize what kind of problem there is I would be much interested. > > > > /Mattis > > > > >
