Steve Anderson wrote:Yep Steve, an increase of C57 would appear .....
The more I look at the circuit the more I see...perhaps also C52/53 and C49/50...again try it first, it may well be fine. I'll shut down the other monitor now to get rid of the circuit!
Steve Anderson wrote:....otherwise I would still be using my 10 year old Motorola but I couldn't find a replacement battery for it...ho hum...planned obsolecence? Never!
Panrock wrote:...because the British 405-lines could sometimes relapse into being no more than 202½
Panrock wrote:...there are two problems to fix. The first is the presence of some RF 'herringbone' interference on the picture. The second is that the frame flyback is now too sluggish with C43's value tripled and the frame timebase running at 24/25 Hz.
Steve Anderson wrote:Rapid progress indeed!
Steve Anderson wrote:This is usually some RF/IF related problem (not that the Argus has an IF), either cross-mod from another (unknown) carrier or something isn't quite stable. Or it may be the RF level is a bit high, but if it were OK on 405...
Steve Anderson wrote:The flyback problem may be due some time-constant shortfall. First thoughts were C61 (30nF) but as this is rated for 2.5kV it may be difficult to increase the value. Also C40 (10nF) may be worth a look at. If possible have a look at the cathode of V13 and see if there's any tilt in the waveform first.
Steve Anderson wrote:It's kinda odd that all of the SP61's in the timebase circuit(s) have zero bias (except V13), but it obviously works!
Steve Anderson wrote:I was going to suggest providing a baseband input yesterday which if the 'mechanical' standards are not composite a simple mixer to glue on the syncs would be required. This may also help identify if the herringbone pattern is coming from the RF/video section.
Steve Anderson wrote:Seeing you have built this as an almost exact replica of the PT article I understand if you don't wish to add other 'features' to it.
Panrock wrote:Unfortunately a 'mixed syncs' feed does not appear to be available from the WC-01 for the mechanical standards. Instead, you get (in essence) a choice between line and frame square waves. See the Manual ('resources' below). My converter is version 2.1. ...I am relaxed about this. After all, if it had been true to the original article it would never have worked! My immediate time for playing with this runs out at the end of the week. So thinking about how to get the unit to display 'mechanical' standards could possibly be tackled in a more leisurely way, over the weeks to come?
Steve O
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