Moderators: Dave Moll, Andrew Davie, Steve Anderson
Steve Anderson wrote:Harry, I tend to forget people have junk-boxes full of stuff, so it does make sense to use what one has instead of buying.
Yes i scrap stuff all the time ,i tend to just buy solder PCBs ic's never buy resistors or capacitors or wire ,i don't think i could do the hobby with the price of a project if i had to buy every part every time.The second stage varies a bit with a change from BC109Cs to either BC108s or BC107s, it's mainly in the biasing but it should still work OK, the AC (signal) gain is virtually unaffected. See below, Red=109Cs, Green=108s, Blue=107s.
Oh thats good it still should work i can tell from the stages that do work in my own low tech way the tranys should of been ok but better hearing it from you !Try turning to pot to minimum gain (maximum resistance) first and slowly wind it up...
I'll give that a go might have time tomorrow to have another look at it .A battery is a clead supply, true, but even 15cm of wire from it to circuit = inductance, significant at times. It also has internal resistance. Decouple/bypass my man!
Steve A.
Steve Anderson wrote:The problem with Darlingtons is 1) a lack of speed, but for NBTV it should be OK, 2) saturation voltage is somewhat higher at 1.2-1.8V, but that also can be negated. 3). They can also be noisy. It IS worth trying though.
Steve A.
gary wrote:Harry TBP has an invert audio feature as well (under settings/soundcard).
TBP also has a scope function so you can actually see the audio and therefore determine whether levels etc. are ok.
TBP also has the advantage of allowing you to turn off sync processing which is often the main cause of picture breakup.
gary wrote:Harry I have had a good look at your wave file - I don't know how you can say it is inverted as it is more or less symmetrical around zero - in other words you have a positive going pulse and a negative going pulse - either one could be the sync pulse.
Well i wasn't to sure which to use out of that monostable the one out of pin 7 looked correct ,didn't know it didn't matter .
My other go at a video sync mixer had a sync level control this one doesn't it seems a bit loud to me when mixing it i might stick a pot trimmer in.Here are videos taken by TBP V2 alpha - one with sync processing (this gives a good indication of how close to speed to are, and the other with sync - these videos are exactly what I would expect your picture to look like.
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