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Originally Posted by Chris K
I'm a little more advanced but not much! I've managed to get a couple dozen of these postwar sets up and functioning pretty well. I love most the TVs from 1947-1955 with RCA as a favorite brand. All sound advice here. I'll add a couple from a beginner's perspective. Wait until the real experts here chime in and point out any mistakes I've made before you employ my suggestions as technique:
1. All of the warnings regarding hot chassis, high voltage often in the 10Kv range and above are the first and foremost thing that needs to be respected. One thing I've heard is the HV anode can really hurt but the voltages in the flyback can kill you. High capacitance, new and old, electrolytic caps can hold charge for a while, especially ones in the power section. They don't hurt...they just give an uncomfortable buzz.
2. Don't buy cheap, hard to believe how many you can get, electrolytic and film capacitor "sets" from China. When I searched Amazon, I was astounded I could get 100uf electrolytic filter caps at a little more than a dollar per cap, so I bought a ton of them. They caused more issues than they were worth. I could not run down a horizontal instability issue in an 8" RCA PT-8-3034. Turns out it was the main "Uxell" filter cap in the power supply that created all the issues. Don't buy cheap stuff. You can use these to test something...just as a tack in but don't rely on them for service use and if you have a problem, suspect them first.
3. If you buy old analytic equipment, be sure it's working well and you can trust the results you are getting. Again, a lesson I learned in the TV school of hard knocks.
4. Don't replace everything first and then test. Start with the power supply. I have a dim bulb setup and I start running the TV with a 60 watt bulb for about 15-20 minutes and then progress through 100, 150, 200, 250 and 300 watts. REMOVE the lead off the horizontal output tube until you get to the higher wattage bulbs. The horizontal oscillator will not start until it gets a certain voltage and the lack of oscillation can drive excess voltage through the Horiz. Output Tube (HOT) and fry it. If I suspect the main power electrolytic caps are bad and can't be reformed or test shorted, I'll replace them before first power up. A shorted electrolytic in this section can fry the power transformer. Ask me how I know that!
5. Service Power, Sweep and get a raster...then go for a picture. Check the TV function often if you can. Don't get carried away and replace a dozen caps and resistors to find you don't have a working TV. You won't know where to start to run it down. If you test...replace...test etc. it's the easiest way to be sure you don't create issues rather than solve them. Again, ask me how I know that!
6. Find the expert restorers on YouTube and watch their videos. My go to are Bandersentv (he posted in your thread) and Shango66 but there are many others.
7. Test the CRT before you do anything else. A dead and rare CRT is usually a showstopper unless there's a way to modify the circuit and substitute it with another type CRT.
I'll probably think of more from the rookie mistake file I have. The experts here sometimes forget how stupid the novices are! Not their fault. When you talk like you know what you're doing they assume you know what you're doing!
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As much as it must have sucked, your sharing of past experience is VERY helpful. The CRT was also my first plan of attack… I pray it’s still functional but I have yet to get a good look (been a bit busy with the job sadly 🙄 hopefully this weekend). Anyways, all noted, thanks!
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Originally Posted by JohnCT
There are three other "hard parts" (auto transmission reference) in a TV that can be showstoppers besides the picture tube - flyback/HV transformer, deflection yoke, and power transformer. The vertical output transformer can also be an itch but those are easier to fudge with a similar but not exact replacement.
Your idea of rebuilding the power supply is a good one (I'd disconnect the chassis and use a dummy load). This will at least eliminate the power trans. Getting the sweep up next is also a good idea. If you can get HV, then fire the parts cannon at it.
John
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Sounds good, I will be doing so. Rather not waste all this time if I can determine that there’s very little chance of resolving the current issues.
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Originally Posted by Electronic M
Some recapping advice: never go lower on voltage rating (you can go higher, although more than double typically isn't recommended), but never lower. There are pre-war and post-war standard capacitance values. Both coexisted in the 50s-70s but the pre-war values are either NLA or stupid expensive. Prewar standard capacitance uF values were 10, 20, 30, 40, 50, 60, 70, 80, post-war values are 10, 22, 33, 39, 47, 56, 68, 82 and various decimal relocations there of. Don't waste your money on pre-war value parts....Get the closest post war capacitance value and you'll be fine (especially on lytics where the original tolerance was shockingly broad). On multi-section electrolytic caps use several single section caps to replace it....There are companies that make replacement multi-section caps but they are generally not worth it unless you are restoring a holy grail model worth 4 figures.
Short leads can make things harder. Just radios and Bob's capacitors both only sell parts with good lead length, but are more expensive and shipping takes a long time. I typically buy from Mouser or digikey. For lytics I favor Panasonic, Nichicon, and Illinois Capacitor, for film caps Panasonic (especially the red ceramic cased film caps), Illinois Capacitor, and WIMA. You have to look at the data sheets and part numbers to make sure you're ordering the long lead film caps.
Don't replace capacitors under 1000pF/uuF which are almost always mica...On the flip side caps 1000pF=.001uF are just about always paper (and should be replaced) even if they're disguised in the same domino cases associated with micas.
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Was unaware about the tidbit regarding the paper caps… VERY happy that you shared that. I’ve been hunting down some of the electrolytics stated in already… seems some are pretty tough to find already (10uf 600V… yeesh). Still looking though. Thank you!
Quote:
Originally Posted by Chris K
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Haha yes, I also have F5. I usually use it on sliders, but considering how much older this thing is compared to my usual repairs you may be correct. Thanks!
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