Barry777
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Jun 7, 2010, 12:43 AM
Post #10 of 20
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Re: [heviarti] Need pointers RCA VGT650
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Hi Buck,
I finally started cut-and-pasting your questions into Word and sliding it over to the other screen to make it easier to reply to your messages. First, I wouldn't worry about posting too much stuff on here, as that is what forums are for. As long as the posts are on topic and free of malice, I've never had any trouble on any forums.
To answer your questions/discussions in order: You'll need most or all standard values at one time or another when recapping, so I would simply order 100, 500 or 1000 of each value. As a general guide, I stock .1 uF, .33 uF, .47 uF, .68 uF, 1 uF, 2.2 uF, 3.3 uF, 4.7 uF, 5 uF, 6.8 uF, 8.2 uF, 10 uF, 22 uF, 33 uF, 47 uF, 68 uF, 75 uF, 82 uF, 100 uF, 220 uF, 330 uF, 470 uF, 560 uF, 680 uF, 750 uF, 820 uF and 1000 uF. To keep stock easy to manage, I buy all values at 50 volts or 63 volts. You'll notice that these standard values are the same for resistors, substituting ohms for uF. In almost all cases, a 63 volt cap will work fine where a 16 volt was used (example) and will last longer. The "experts" will tell you that a 16 volt cap has a different ESR than a higher voltage cap, but I've never had a problem. These guys are probably engineers, and we lowly techs go behind them and install multiple mods to make the unit actually work after they so expertly design them.
When recapping, I always put a magic marker dot on each one as soon as it's soldered in for two reasons: So I don't replace it again, and so I can tell at a glance whether I've already recapped any given board. The more of each value you buy, the less they cost per cap. Just one tiny example: One cap costs 15 cents at Digi-Key, but 1000 of them costs $27. This reduces the price per cap from 15 cents to just under 3 cents. I use Digi-Key and Mouser. Forget - I repeat - forget Radio Shack (or any local hangout) for parts - it's more frustration that it's worth in this day and age. Even their connectors are cheap and go intermittent in a short time, and their selection of parts has been reduced to a tiny handful to make room for more cell phone accessories, and so they can hire know-nothing teenage girls to work behind the counter.
On the Magnavox, my book crosses the VJ8220 to: Panasonic PV-1100, JC Penney 686-5001, Philco V-1100, Quasar VH-5010, RCA VCT-201, VCT-300, VCT-310, VDT-201 and Sylvania VC-2500.
"Screwy video output" can be hundreds of things both electronic and mechanical, thus reinforcing my suggestion to dive into those books :-) It sounds like you need a tuner alignment, video alignment or both. Also, the RF modulator box could be off peak, reducing the signal enough to bury the sync pulses in noise. Any machine that age with so much discrete analog circuitry would need to be aligned to perform properly - and it likely would benefit from a full recap job. A full alignment requires test equipment and the service manual, and no amount of playing around will fix that. A quick-and-dirty check of your video heads can be done by gently rubbing a fingertip over them. If you don't feel them protruding a little, they're very worn as they need to actually penetrate into the tape a bit, rather than just "see" it as in the case of an audio head. I can understand the lack of spare cash (as I think we all experience), and service manuals are quite expensive in my opinion. If I had to choose only one book, I would probably go with the service manual for my favorite machine - it's that helpful - and glean the rest of my knowledge from Google searches and such. In fact, the many websites devoted to basic electronics tend to be more concise and real-world than any book I've picked up - and I have literally hundreds of electronics books. On diagnosing your screwy video, it would be helpful to understand exactly how the video is formed and processed, then how each component contributes to the output. Once you know all that garbage, it can take many hours of thought, analysis, schematic-studying and experimentation to finally determine the problem. In many cases, you arrive at the solution by knowing what's NOT the problem. Remember Apollo 13, "What do we have on the spacecraft that's good?".
Not to be insulting, but you seem to zero in on very old equipment that needs much more work than you have the resources for (mainly test equipment and service information). When you can get a slightly newer unit that needs only minor and routine mechanical atttention for $15 at a thrift shop or yard sale, why drive yourself crazy trying to nurse the ancient stuff back to health? Just a gentle tip - that very old gear won't be fixed by changing a part or tweaking a pot; it will require a full alignment (minimum) and a complete recap to even have a chance at performing properly again. For an alignment, you need at least one RF generator, a good scope, a video generator, a few Tentel gauges, and sometimes special jigs and setups created by the manufacturer for performing one adjustment for that one model only. If the faces are greenish or purplish, then you'll need a vectorscope for the color circuits. Doing extensive work on a VCR that age is quite an undertaking, and only a well-equipped shop would be set up to handle it. In short, you would need to put out at least $1000 to have the necessary gear to align a VCR - and that's talking current USED prices for the equipment and gauges. VCR's are something you generally can't tweak "by ear" because of the critical synchronization of some circuits, though you can usually adjust the guide posts and A/C head by simply watching the screen and listening to the output. But that is mainly just to clear up a minor tracking problem or muddy audio.
On testing the voltage going to that trimpot in your receiver - simply remove it from the board and probe its connection points on the board. I'm sure you'll find some DC voltage that shouldn't be there. Heck, the unit might even still work without the pot and you're off the hook! Lots of components are only there for temperature stability, noise suppression, bias, etc. If the unit will still work without it, what the heck? I can't tell you how many times I've bypassed a nuisance protection circuit and lived with the "pop" when you turn it on - on my own stuff of course.
You don't want ME working on your stuff - I'm the most expensive independent tech I know of. I've done most of my work for classic car owners, who are already spending anywhere from $25,000 to $100,000 restoring their ride. A few hundred bucks extra to fix the radio is nothing to them. Thus, my minimum to even set a customer's unit on my bench is $150, and my flat rate to repair and recap a 4 channel home receiver would be somewhere in the $400 range. I do what any other business does - find out what makes the most money per time spent, and drop everything else to make more time for it. I don't keep any cosmetic pieces around such as knobs, buttons, faceplates, etc. I'll probably fire the business back up in the next month or two, as I need to come up with megabucks to replace all my plumbing, HVAC ductwork and insulation to try and keep the wife healthy. Found some mold under the house from leaking plumbing, which has gotten into the ductwork, and I'm not one to crawl under the house every few months to fix one thing - it's all coming out and all new stuff going in this summer. When I fire the website back up, it will fully explain my prices and terms, and I'm toying with the idea of including VCR's this time around - but mainly mechanical service that parts are still readily available for. This deal of searching eBay and everywhere else for parts and parts units is not my cup of tea, not to mention the constant clutter and need for organization it creates. When I'm not beng the biggest slob in the world, I'm a neat freak - if that makes any sense!
A quick summary of your situation is that I don't think you have what you need to fix this old stuff, and you should probably look for cheap newer equipment. At the very least, you need to get a few books and the service manual for whatever you're trying to fix. Without that, there's really very little we can realistically do to help you. Sorry, just an experienced observation. I'm definitely not the best VCR tech around, but I know enough to know when I'm wasting my time. I think you might be wasting yours, given how much less you have to work with than I do at this point.
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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
(This post was edited by Barry777 on Jun 7, 2010, 2:42 AM)
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