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#11
03-09-2017, 09:49 PM
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Out of curiosity, I built that preamp/inverter on a piece of perfboard, using a 12V battery supply and a 2N3903 transistor:
 It works, after a fashion, but it isn't great. The first pic shows the video signal (color bars) direct from the pattern generator:  And below is the signal coming out of the preamp. The pattern is inverted, but kinda "slenderized," and there seems to be some noise or instability:  The screen image is disappointing. It has decent contrast and detail, and the pot on the collector acts as a contrast control, but the vertical is quite unstable and retrace lines are visible nearly all of the time (not much in this pic, though):  I wonder if the 2N3903 transistor wasn't the best choice? The local supplier didn't have much to pick from. Here's the 2N3903 data sheet: http://www.brown.edu/Departments/Eng...s/2N3903-D.pdf Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html Last edited by Phil Nelson; 03-09-2017 at 10:05 PM. 
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