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Post by gjaky on Jun 21, 2014 6:43:24 GMT -5
Did you end up trying to feed the RGB straight to the neckboard? Yes, that was one early step, that's how I got suspecting the neckboards. |
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Post by gjaky on Jul 16, 2014 7:25:14 GMT -5
So after a short break, let's prepare for round two.
This time I will use big boys toy's as well, as I arranged a good deal on a 500MHz active FET probe (HP 1120A), I believe this will make a good pair with my HP 1720A oscilloscope, and will let me take accurate measurements on the HF performance of each stage.
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Post by gjaky on Sept 13, 2014 6:51:52 GMT -5
Unfortunately it turned out that the probe had a defective DC restoration circuit (not important for these measurements, but why not fix a broken circuit?  ) also the divider which came with the probe didn't work well, so I had to look for new dividers, then I had to spend some time to find out how to compensate the new dividers to the probe. And since these were as-is items I had to check if they are really up to their specs (roughly at least). And finally had to find some spare time to play with the circuits. Originally I wanted to test a PG xtra neckboard as well, but I wasn't able to feed the board with the appropriate input signal (4Vpp signal on 3VDC). So jumped to the XG boards again, with the FET probe it again became obvious that the sony preamp IC isn't that good as the spec. sheet says, (they claim 2ns rise time with 4Vpp output) while I only measured only 3,5ns at 2Vpp (~100MHz). The discrete preamplifier board seems to be quite good as it doesn't really affect signal speed, and now I measured nice shaped signals throughout to the input pins of the videopacks. The output of the videopack is still poor in speed, though no odd distortions as earlier, about 12ns rise time, which means 30MHz BW. This seems to be believable based on what I can see on the screen. Of course the question still remained: Why this low? But this time at least the measuring equipment can be ruled out from the faking factors. More to come... |
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Post by gjaky on Sept 13, 2014 11:31:55 GMT -5
So, I managed to get the PG xtra neckboard working, figured out that I can use the preamplifier on the XG neckboard to drive the PGx's, the VPA13 on that board performed considerably better, measued 4ns rise time at 55Vpp output, and since the input wasn't much faster than that this is a very good result. I have to conclude that the problem must lie in the XG's board (material) then, since I already swapped the output ICs multiple times, bypassed all possible components that can load the output of the IC, and the VPA13 can perform much better on the other board even with the preamplied signal from the XG board. This also means there isn't really anything I can do to make them better now.
What do you think MT, am I missed something should I check anything else?
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Post by mastertech on Sept 14, 2014 19:07:57 GMT -5
An ic's performance (or any component or circuit) is only as good as the juice that runs it.  |
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Post by gjaky on Sept 15, 2014 1:09:31 GMT -5
An ic's performance (or any component or circuit) is only as good as the juice that runs it. Yes, for these tests I built a simple powersupply with the needed voltage for the neckboards, so they are different from the machine's supply. Plus when I tested the PG xtra board tied to the XG board I used the same power supply, the PG xtra was good, the XG board wass bad, the supply was the same. |
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Post by gjaky on May 18, 2015 13:59:47 GMT -5
So I got the power supply from Scott, that was made at VDC to mate the Marquee neckboards with the Ampro projectors. So it looks like I have all the main parts to start the NECrohome project   |
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Post by mastertech on May 18, 2015 16:40:15 GMT -5
Cool. I will be curiously watching to see waht you find. Why don't you invite Scott here to help assist if he can? |
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Post by gjaky on May 19, 2015 0:34:55 GMT -5
Actually he already helped me so much that I feel shame to ask more... To say the least I got this power supply absolutely free, he not even let me to cover the shipping costs... |
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Post by Casethecorvetteman on May 19, 2015 2:21:01 GMT -5
Thats very good of him!!
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Post by Deleted on May 19, 2015 13:29:47 GMT -5
Great! How does the spotkill and I sense signal go to the Nec? Is that compatible?
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Post by gjaky on May 19, 2015 15:30:35 GMT -5
Great! How does the spotkill and I sense signal go to the Nec? Is that compatible? The spot kill seems to be compatible, I sense isn't looking hard either, the biggest problem is that there is a gain (contrast) trim pin on the XG neckboards, that is not present in the VNB, and I really don't want to poke with analog multipliers in this project. |
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Post by Deleted on May 19, 2015 17:49:28 GMT -5
Ok. Think I can not help much with that. However this makes me think perhaps a Marquee neckboard could work on a Barco? If you get this to work it will be very much inspiration for hybrids |
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Post by mastertech on May 19, 2015 20:26:50 GMT -5
Actually he already helped me so much that I feel shame to ask more... To say the least I got this power supply absolutely free, he not even let me to cover the shipping costs... I invited him. He's going to drop by and have a look see. How are the CRT pin outs on the Marquee vs the NEC tube? Which NEC tube are you going to try on? |
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Post by gjaky on May 20, 2015 0:47:24 GMT -5
Actually he already helped me so much that I feel shame to ask more... To say the least I got this power supply absolutely free, he not even let me to cover the shipping costs... I invited him. He's going to drop by and have a look see. How are the CRT pin outs on the Marquee vs the NEC tube? Which NEC tube are you going to try on? Currently I have no NEC spare tube, so I have to make absolutely sure on the bench the spotkill works as it should before putting in the machine... Not the pinout is the biggest problem with the E'home vs. NEC but the tube socket, the NEC tubes use the thin-neck tube, therefore narrower CRT socket, I already have a few ideas to overcome this, will turn out which one works best |
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) also the divider which came with the probe didn't work well, so I had to look for new dividers, then I had to spend some time to find out how to compensate the new dividers to the probe. And since these were as-is items I had to check if they are really up to their specs (roughly at least).
