Barry777
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Jul 4, 2010, 7:26 PM
Post #46 of 98
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Re: [heviarti] Kinda OT, one for Barry or JTS.
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Did some more research about TBC's, Macrovision, etc. From what I've read and heard from former JVC techs, all you need to defeat Macrovision is to be able to disable the video AGC (Automatic Gain Control) while recording, since Macrovision disrupts the AGC that is a "forced" option on all consumer-grade VCR's. You'll be able to disable the AGC on your 822, so I guess we'll know for sure 'cause I'm too lazy to try it on mine. Of course, it's unlikely that a consumer DVD recorder will have that option anyway, and the video AGC is switchable only in Record mode - so you'll still need your TBC. for transfer to DVD.
With older anti-copy systems like CopyGuard, it IS the actual timing pulses that are messed with, and a TBC is absolutely needed to restore proper timing. Apparently, your TBC does more than just correct the sync, since you're also able to defeat Macrovision with it. A true, professional TBC uses separate connections for Y (luminance), R-Y (red minus luminance) and B-Y (blue minus luminance), and naturally requires corresponding connections for anything connected to it. Possibly, there are different types of TBC's from simple video stabilizers for home use, to the stuff I don't yet understand that will hopefully be on your 822 also. We'll have fun learning about them.
On the scope issue, I think the analog Tektronix will be much easier for a novice to figure out, as there will be more hands-on front-panel controls and less stuff hidden behind menu trees. Also, analog scopes show the wave instantaneously, whereas there is always a slight delay with a digital scope while its internal computer processes the information. This means that a digital scope will have a somewhat jerky response when you're testing the action of, say, a volume control - and will make it look like the control is not smooth. Digital scopes also have wayyyy too many features that will only confuse someone unfamilar with their basic operation. For right now, you want to learn how to use one and perform basic measurements - you won't need to confuse yourself with how to expand the wave for easier rise time measurements, or how to delay the sweep to examine a tiny part of the wave for noise or glitches, etc. You'll want something that you can learn to trace signals with, not something that takes hours to figure out how to even SEE the signal. Another factor (not really that important) is that video signals go as high as 4.5 MHz, but you won't need more than 20 MHz for most troubleshooting anyway. 375 MHz will give you a brighter, sharper and more stable trace at higher frequencies. Digital scopes also usually have a lower maximum input level since they're made more for digital troubleshooting, and it's not hard to fry the input amplifiers on them if you're not very careful.
Some digital scopes DO have one really cool feature though - automatic scaling. On an analog scope, you need to set the vertical gain and time base to match that of the wave you're measuring, which I usually do just by experimentation - flipping both until I see the wave, then fine-tuning it to see it better. On most digital scopes, you can just hit Auto Scale and the wave will pop right in perfectly. But this assumes that you already know how to use a scope in the basic sense. You'll cheat yourself out of 95% of the learning process if you start right off with a digital scope with all its automatic functions. If you also have access to the user manual, then it's a slightly different story. My digital scope is an HP 54201A, and most of the operations are probably fairly similar if you just HAVE to play with a digital scope to start off :-) The BAMA website might even have the user manual for both.
As a side note, I finally dragged out my digital scope yesterday, and set the manual next to it while I fed some test signals into it to figure out how to use it. Have to say, I don't see myself using it very much, unless I have some really unusual timing issue in a circuit that would be easier to see on a digital scope. Otherwise, it was a lot of work for a little payoff (sort of like trying to make money playing music). For the stuff I do on the bench, an analog scope is simply much faster and easier in most cases.
So it's pretty much up to you which one you choose. If you want to learn how scopes work, how to get good at using them and ESPECIALLY want to spend your time learning how to troubleshoot electronics, definitely go for the analog that you can figure out quickly. If you go with the HP, you'll also learn a lot - but it will be information that applies more to that particular scope, not really stuff you can use after you give it back. Most of the experienced guys at work, as well as myself, much prefer an analog scope for troubleshooting. Digital scopes are only better for certain isolated applications, and can be a real pain in the ass when you're trying to get stuff done. Since I work many benches and many products, I use a different scope every couple hours sometimes. You'll hear me cussing and saying "how do you get this damn thing to work?" fairly often when it's a digital scope. And we're not supposed to be cussing at work :-)
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Barry Fone - VCR Repair hobbyist and professional FAA Repair Station Avionics Bench Technician (top level). TEST EQUIPMENT: (4) Sencore VC93 VCR Analyzers, (11) Tentel gauges, Sencore VA48 and (2) VA62 Video Analyzers, Sigma Electronics TSG-375 NTSC/SMPTE Video Generator, several VCR Alignment Tapes, plus countless Oscilloscopes, Frequency Counters, Wow and Flutter Meters, Distortion Analyzers, Vectorscope, 136-channel Logic Analyzer, Signature Analyzer . . . . VIDEO GEAR: (6) JVC BR-S822U's, (3) JVC BR-7000 series, (3) JVC BR-S500U, (2) JVC BR-S800U, JVC GR-800U and (2) GR-860U Editing Controllers, Sony FXE-100 Video Switcher/Effects Generator, (5) Time Code Generator/Readers, (1) Sony SLO-1800 (Beta), (2) Alesis ADAT-XT, (1) Sony DXC-1200 TV Camera, Pioneer VP-1000 Laser Disc Player plus many consumer grade Beta and VHS VCR's. Passionate electronics enthusiast since 1973...most anything except computers. Check out my collection at www.barrys8trackrepair.com/MyVideoGear.html
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