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Old 12-11-2019, 09:11 PM
Yamamaya42's Avatar
Yamamaya42 Yamamaya42 is offline
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Join Date: Nov 2018
Location: Round Rock TX
Posts: 3,203
I still cant help but wonder what is causing the slightly annoying retrace lines to show up sometimes.

CRT age? No idea, the bias is at lowest setting, did grayscale setup a million times, no help. Will still show up when I turn up brightness high on some scenes, no matter the video source ( NOT macrovision )
Other than that picture is fine.

Still not quite sure how the horz blanking works yet. :/
VERY strong horz pulse from FBT on grid 230v @ -80v dc (on my TV ) , shows 115v on plate, goes to CRT bias switch and .22 uf to the Y amps. Shows it to be 15v on SAMS on bottom of tree, ( was 8-9 max on mine )



This is what I find a bit confusing and don't quite get, the Cathode of the blanking amp ( Cathode follower? ) is tied to the cathode of the bandpass amp.
Shown to be at 5v, no other info ( waveforms )

no cap or resistor on the blanking amp, but the bandpass has a 820pf 10% and a 390 ohm res, both replaced by the person before I had it.

I have seen no color problems since I got the color to work, and I DID check the resistor and the value of the cap looked OK, but I did not make sure they were exact.

Now since I really do not understand the circuit, I wonder, could this resistor / cap effect the blanking amp?
YES the 6gu7 is new, the 6gh8a is not.
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