RCA 721TS resto (directors cut) part 1
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- เผยแพร่เมื่อ 24 ก.ย. 2024
- I did a short video on this project a few months ago. Well, here is part one of the extended version. Lots of challenges in this one and I think you will really enjoy it. Lots of good troubleshooting and replacing some parts you may not have had to deal with before.
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I am all for the stories, ramblings and conversation.
I like this new format. ive watched your videos for a number of years now and its nice to just chill and enjoy the storys. it'll help more to learning
Rock'n the 1979 shirt!
Nice mention of Alex at Technology Connections (and Technology Connextras). His channels are excellent at explaining the principles behind everyday tech. Although very different in style, his work reminds me of a 1980s TV series we had in the UK called "The Secret Life of Machines", presented by Tim Hunkin. He gave superb demonstrations of the engineering fundamentals behind everyday items - including TVs (the TV episode memorably ended with a huge bonfire of powered scrap sets, very Shango EOL). All of those episodes are on TH-cam with an updated commentary at the end, as well as much more recent ones about engineering components and his novelty arcade machines.
Oh yes. I've watched those many, many times. Had a big influence on me :)
@bandersentv And on me too. Very good to know that Tim's influence has reached across the world - a tougher start for him pre-Internet :-) I do think it is very encouraging that there are so people devoted to putting really intelligent and informative content out there, we hear so much of the nonsense but I am sure that the good is dominant.
Got to watch Shango every Saturday. Always entertaining, speaks his mind, and I learn something. Haven't tried removing a cataract from a color TV, kinda scary, and I have one that needs doing. Keep kicking that can down the road.
@@rossthompson1635 we were lucky that public television recognized the value and broadcast Tim way back then
Thank you so much Bob. The 721 TS is already sitting on it's original stand and rocking my world. Also with the colder season coming in few months this tv will make a nice heater. Once again I am very happy with the work you have done.
That's great to hear. It was a challenging and fun project
That was a nice blue pop when that tube blew. Those used to be fairly common, like the 5Y3. I still have boxes of radio and TV tubes from when I was fixing stuff.
I used to use that same 9 inch Sony portable TV on my bench. Now its just displayed in my living room.
Try mineral spirits and fine steel wool on the chassis.
why I use a solid state 5u4 and dim bulb. No control with a veryaxe
👍 dim bulb protects against dead shorts,variac pretty much does not unless you're able to monitor current and know what the current should be.
I would if I could find it. I have a couple around here somewhere
@@bandersentv You can make one out of the tube that popped.
@@bandersentv You can make one out of that tube
Reforming the electrolytics on these early sets has got to be tricky. My preferred way to reform is by using a lab DC power supply with a resistor in series to limit current to microamps. However, with the B+ powering the focus, image centering, and ion trap, a huge amount of current gets thrown away in voltage dividers, so you don't really know if the cap or voltage divider is sinking current. Also, since there is so much power dissipated in the voltage dividers, it is common for one or more resistors to burn open. Without a normal B+ load, the electrolytics that are getting B+ are probably receiving over-voltage. Partially reformed electrolytics act like a zener diode, which may be what caused the 5U4 to blow when you cranked up the variac..
The voltage dividers may also interfere with your cap checker's leakage test.
The seals on those Twist-Locks looked badly blown. Makes me wonder if the set had been turned on several times in the past after years of sitting idle. I think that RCA font on the newer tubes took place in the 1960's.
33:00 Sometimes I hook up a 100 microamp meter in series with my Heathkit capacitor checker so I can watch how the current is tapering off as capacitor forms. Of course, during heavy charging/discharging you have to remember to shunt the meter or switch to a higher scale. Kinda risky with an old analog meter, you risk damage to the hair spring on the meter if the capacitor shorts during test.
40mfd @ 350vdc should plateau at no more than 500 uA worst case leakage or thereabouts.
Never seen a 5U4 let go that fast. Usually a pretty purple color, red plate, or the transformer starts to groan and gets louder and you get some warning. AA5 am radio the 35W4 pops pretty easy, that is the fuse, the cathode wire burns off.
If it was out in the desert , then Crazy Shango wants it
😊😊😊🎉🎉😊😊
Using an incandescent lamp in series might have protected that tube from blowing. Or not?
Bob, is it really a complete package unless it contains the owner’s manual, service manual, and the unreturned “NO POSTAGE REQUIRED” factory warranty card?