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tnt23

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About tnt23

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    Saint-Petersburg, Russia
  1. Connector on a wire is good idea, will consider this for future mods. It's a shame sound cannot be squeezed in S-Video, but then there are SCART connectors.
  2. More pictures taken on PVM monitor: Color smear on vertical lines is a bit annoying. I will take another round of color taming, just need more courage to again dismantle the case and handle those deteriorating ribbon cables. S-Video socket fitted on back of VES case:
  3. @e5frog I have tuned the pots to set 1Vpp on S-Video connector pins, after the THS7314. Without lowering input signals to THS7314 its outputs went to good 2 or 3 volts swing. Perhaps I should indeed tweak luma down to 0.3Vpp, just left it where the colors on that old LCD telly seemed all right to me
  4. The schematic is mostly copied from TI datasheet: On VES, took color signal from C28 to pin 3 of THS7314, and sync from 'VIDEO SHT 1' point to pin 2 of THS7314 via 4K7 pots (not shown). Used those pots to set the voltage swing of signals on S-Video connector to ~1Vpp. Did not register any checkered flicker, but that's probably because I was more obsessed with color ghosting. Will post more closeups.
  5. Inspired by your progress, I took a closer look at my own mess of wires and immediately discovered that output 75R resistors on the proto board did not work, being short circuited by unfortunate track pattern on the board's bottom. I have no idea why I did not pay attention when I was soldering these. As the result, luma was working without proper line termination more or less okay, but chroma has been distorted savagely. Now everything looks much better. I fitted S-Video socket on the rear part of VES case. Here's the picture on an old LCD TV with a lousy S-Video cable, hence the ghosting.
  6. Nice and small one. Alas, according to the datasheet its maximum current is 1A, three times less than that of original LM7803 in TO-3 casing.
  7. Lost my +5V rail again, don't know was it due to short circuit or overload. Not wanting to fiddle with another L7805 in TO-3 case (which are of limited availability locally, and rather pricey), decided to go for DCDC regulator instead. Got a 5V/3A assembled kit for about $3. That one came on aluminium PCB to be conveniently installed on heatsinks. Fits pretty well with some wires: And stays cool after 40 minutes work, worth the hassle.
  8. Could've saved me some efforts if only I haven't overlooked a THS7314, same as THS7316 but for SDTV (with 8MHz filters) LOL!
  9. Schematics for Luxor differ in couple of moments, firstly Luxor appears to be PAL version and features dedicated delay line, and secondly, they have omitted LS07 gates after 74153 mux for CHROMA and BURST signals. Luxor also swapped another LS07 gate in Sync circuit for open collector BJT, but this really should not matter.
  10. Did you get a chance to try it? I've built this circuit to try something different while still getting frustrating results with THS7316 amplifier. It did not get me any better results though. I will be trying a couple of other ideas, one is to make a copy of delay circuit that shifts 3.58MHz carrier phase for Green and Red: Just to check if everything is fine on this path. Warning: bit of tech whinning on THS7316 inside! And as an absolute last resort, I will try making RGB output by means of 256x4 EPROM (82s126 or similar) and a bunch of emitter followers. EPROM is there to translate BG0, BG1, FG0, FG1 signals directly to RGB and (I)ntensity to make light hues of Green and Blue and Grey.
  11. Could be, still would replace the bridge as it was getting too hot. I've found compatible BR310 replacement, 3A continuous, will give it a go. This is what I'm really tempted to do, as +5V was rather messy on the scope. Besides, those brown disc capacitors are used here and there in video generating circuitry, so worth checking, too.
  12. Problem is, I cannot get decent composite in the first place. Splitting to Chroma and Luma did not help much. No I haven't. so far everything I've been checking did comply with the schematic. By the way, the +5V bridge rectifier was getting rather hot, and at some point +5V had just gone. I have desoldered both the bridge and the 7805 for replacement.
  13. So I decided to try S-Video: lifted C28 and fed it via spare THS7316 channel to pin 4 (C), and connected Composite output to pin 3 (Y): Blue looks absolutely gorgeous. Red calls for help, and white background is decorated with some green hints. Vertical lines test is also great on Blue. I think that's because the top half of BURST mux E3 outputs zero when Blue is to be displayed: While for Red and Green (and black) 3.58MHz subcarrier is present on BURST line. Still I don't understand this.
  14. Did a better grounding, and indeed it results in wide horizontal color bars. Cool for hacking, don't know what I could use these for Regarding empty bits 0, 1, and 4 on 74145, I guess they default red background to black maybe?
  15. Yes, on my PCB 74157 is soldered, not 9322. As far as I understand, test points marked A5-xx and C6-xx relate to empty sockets on the PCB. Handy if you want to check certain signals, but also can be useful for debugging. For example, TP A5-14 can be grounded, and should select 8V and 16V clocks to define BG0 and BG1 colors instead of those coming from VRAM. (Did not work in my case, don't know if it was me or 74LS298) Interesting to see I1C and I1D inputs routed to VRAM but QC and QD outputs not used. Some rudiments for more colors perhaps? Similarly, TP A5-14 can be grounded to disable pixel data coming from VRAM, forcing all zeroes. TP A5-15 disables Burst Gate flip-flop D4 (and probably ruins video sync), which also disables palette data storing in C4, and so on.
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