Looking at the boards in the VG91, that may be using a digital video pattern generator system. Instead of various analog oscillators, pulse generators, and modulators for the chroma generation, they create the NTSC patterns as data and load them into EPROMS. Then to produce the pattern, they simply address the EPROM with appropriate timing signals and output the data through a DAC and analog filter. One of the benefits is there is no drift, component aging, or occasional alignment in the pattern generation. The only drift area is the video output amplifier gain and that should be very stable. Some may observe and ask how did they get all those 720x486x8bit patterns on those relatively small EPROMS? The trick is that most test patterns are repeating lines. Like full field color bars, you only need to store one line of digital video. Then just repeat reading that line to fill the raster as needed. Other test signals may need a few more lines stored but none need a full frame or field of video stored. That was state of the art in the late 1980 for broadcast grade signal generators but a pretty high end feature in a TV service product. Sencore often gets an undeserved rap in the broadcast and professional electronics industries as "TV service junk". But IMO, they made some pretty good stuff, close cousins to Tektronix and HP gear.
Great find! Glad to see that the VG91 works and it appears that the others have a good chance of working.
Hello Bob. Nice video - Thanks for sharing this.
Chris's Tech TV posted a SENCORE published VC93 demo vid, it does show it working independently.
Looking at the boards in the VG91, that may be using a digital video pattern generator system. Instead of various analog oscillators, pulse generators, and modulators for the chroma generation, they create the NTSC patterns as data and load them into EPROMS. Then to produce the pattern, they simply address the EPROM with appropriate timing signals and output the data through a DAC and analog filter. One of the benefits is there is no drift, component aging, or occasional alignment in the pattern generation. The only drift area is the video output amplifier gain and that should be very stable.
Some may observe and ask how did they get all those 720x486x8bit patterns on those relatively small EPROMS? The trick is that most test patterns are repeating lines. Like full field color bars, you only need to store one line of digital video. Then just repeat reading that line to fill the raster as needed. Other test signals may need a few more lines stored but none need a full frame or field of video stored.
That was state of the art in the late 1980 for broadcast grade signal generators but a pretty high end feature in a TV service product. Sencore often gets an undeserved rap in the broadcast and professional electronics industries as "TV service junk". But IMO, they made some pretty good stuff, close cousins to Tektronix and HP gear.
Thanks for the insights. I'll be demonstrating their portable VP-401 pattern generator next.
That one piece of equpment that I have been looking for when that unit was new I would dream of it for my shop since I owned other Sencore equipment !
They're not too cheap. Best to make an honest offer and hope for the best.
14:30 meter switch? LED light blinks to warn about safety because of higher voltage.