This Is How I Learned Electronics Repair Part 2
ฝัง
- เผยแพร่เมื่อ 25 ส.ค. 2024
- I think the best way to learn electronics repair is by fixing things. A great way to start, and the way that I did it, was by building electronic projects I found in books and magazines and fixing them when they didn't work. Usually because i had done something wrong! A good thing about this learing method is that you have schematics and often a description of the circuit operation. The fact is, if you cant' repair with schematics you ain't gonna learn to repair without them. Even now I love to play around with projects and still find problems that challenge me. Here is a good example. In part one I asked subscribers to make suggestions about what they would like to check, in this part I try the various ideas that were posted.
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Part one is here • This Is How I Learned ...
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Thank you
Richard
Detlef messaged me from Germany (yeah he's on holiday there at the moment) and he picked up an old stock CD4047 so he's bringing that one over with him. Quicker than me ordering anyway. Then the final proof to end this saga 🙂
I've built that just now and works lovely with nice square wave output on both pins 10 & 11, frequency adjusts fine as wel, lot of people are saying fake parts out there !
Here to tell you that you are constantly helping a lot of us with your content, learning, trying and finding enthusiasm to keep learning, really one of a kind on the internet. Hope you have energy and enthusiasm to keep like this for years and decades beacuse we will be here... Learning electronic repair 🙏 huge thanks
Hi Richard. I remembered an old project which used a 4047 (actually ST's HCF4047BE) and I had one left over.
I've reproduced your circuit, using 220nF and 220k ohm that came to hand and it works perfectly. Visually I would say it runs at about 2Hz (the calculated value is 2.35Hz).
I'd agree with the conclusion. There's not really many other possibilities. Someone was cloning those, didn't get it right, dumped them in a skip and some enterprising individual picked them up and put them on aliX
Well done, great video. Also glad to see you clipped those nails friend. Looks a lot better bud. 😊
I just googled "How to test a CD4047 Astable Multivibrator" and the circuit that was shown is exactly like the breadboard setup that you have Richard, I would say that the CD4047 IC's that you have are either defective or fakes, without a known good IC to compare the pinout readings to I don't think you will be able to come to any different outcome.
Glenn
I know it's a few weeks late, but it might have been worth checking with the IC testers anyway. If the IC is a fake or been manufactured/marked wrongly post manufacture, it may have given you an indication as to what it was, or how the tester thought the IC operated.
Back in ‘05, I would order free samples from DigiKey and use an oscilloscope and multimeter ❤
Correct me if i am wrong... Pin 12- "Retrigger". According to the datasheet, the cycle will retrigger if the pin is set "High" (even if the table says Vss for multivibrator? The Datasheet is mentioning that stable Astable frequencies are somewhere in the 10-100kHz, so low frequencies as these in your experiment might work as Monostable and Retrigger is used for increasing the pulse width). What you have on your output now is a single cycle. LEDs go on once and then its over. This is because you have pulled Pin 12 to Gnd (low) if I see this correct on the video. So IMO setting pin 12 to high might fix your issue?? ...
Retrigger and External Reset is actually a cool feature as you can either cycle the outputs all the time or just always once after Reset is triggered.
The frequencies of 10kHz & 100kHz on page 1 of the data sheet, look to me like examples of what stability to expect with temperature variations at those frequencies. I don't think they are any kind of limits. Fig 14 shows astable mode using 1uF & 1MOhm timing components. That's around 0.2 Hz.
Where’s the money in making fake chips, when the originals are already so inexpensive?
Could you drive the gates from the signal derived from the square wave (pin 13) you do get?
I’ve just breadboarded this project and only exception I made (had no other) was I used a ceramic 10nf cap and I’m using a 330ohm resistor from pin 2 to the potentiometer. I have 233khz @ 5.47v dc on one end of the potentiometer and 2.56mhz on the other @ 3.58v dc. I think your diagnosis is correct 👍
Thanks for taking the time to try this yourself 🙂
@@LearnElectronicsRepairspending the time to do it is nothing compared to the time you put in for us all ! Least I could do when I realised I had all the parts. Was fun and I needed something to do 😂 Thanks for all your hard work
@@Mark_C1 To quote almost a meme these days
'This Is The Way'
Everyone wanting to learn take note 🙂Thanks Mark
Heya, oke notthing till now works so maybe it's the ic
Hi Richard. Have you tried + and - supply with a floating 0v?
Go with mouser or rs.
Selling known defective chips not to waste them.
Just to waste others time? But then this turned out to be a great teaching aid, unintended but true
@@LearnElectronicsRepair 40 years ago the USA chip makers worked on 10% failure rate and when Japanese chips started to come on the market an American company ordered chips from Japan and said there must not be more than 10% defective ones· When the company collected their chips they were given two bags one bag with 90% good chips and one bag with 10% bad chips. The Japanese chip manufacturers were working to zero defects not 10%
Haven't watched all of part 1, but building the basic square wave generator (with a 4047 unlikely to have been damaged by drawing too much current from the outputs), with outputs just connected to a scope and nothing else, should be sufficient to test operation. 4000 series ICs are likely to struggle with moving charge rapidly on and off the gates of power mosfets and an interim push-pull stage may be required. This is, of course, only my opinion.
Hi Ralph. Yeah in part one the CD4047 was just connected to the gates of the two MOSFETs on the little red PCBs via 220 ohm resistors. Same problem without an LED load to drive.
I have some 4070BE chips unused left over from a project. I could get some readings off these if it helps
Sure take a look if you like, I did some diode test mode reasings in part one though there was nothing that looked rally suspicious there
A few years ago I bought a large number from Aliexpress = All have that exact same problem...
And they were all CD4047? Interesting.
What 4047's ?
I think they are defective, I looked at the data sheet, you mentioned the pins, but I would be tempted to play with the pins 9 and 12 (change high/low), looking at the Logic block diagram these pins alter the state of the frequency divider, if there is no change in what pins 10 and 11 do when you alter 9 and 12 then that part of the chip is probably broken.
If you want a project on PCBWay I will have to blow my own horn here 😁 you could try my "Tim's PTC Hot Plate Controller" you can also use the project to control the temperature of a basic soldering iron. (If you do, remember to change 5 off to 10 off)
OK, I'll ask for some of those. DIY hot plate for pre-heating is something a lot of viewers are interested in I think. Should be no problem getting that working then 😉
@@LearnElectronicsRepair There is two versions, In the UK as you know we have fuses in the plug. Some US or EU, asked for a version that has a fuse inside.
Take a look at my Instructable, I originally made it with parts off the shelf. Then PCBWay made me an offer 😁
Check that you are able to get the Power supplies I used. I designed the PCB to take a specific one. I would have reverse engineered the power supply, but I have no clue where the get the transformer or how to get its specification.
If it not possible to get them now it's just a small 3W mains to 5 volts PSU.
Was just thinking the same thing about pins 9 and 12 (External Reset and Retrigger). I was looking at the datasheet and if you look at logic diagram, particularly the FF4 part that is the last flip-flop before the outputs, and then look at how they implemented FF4, you will see that it's a D flip-flop with RS (Reset and Set) lines. Now, we see from the logic diagram that pin 9 and 12 are connected via a NOT gate and a buffer to internal R and S inputs of the FF4. And if pins 9 and 12 are LOW, R and S are set HIGH, and those go to NOR gates in the FF4, effectively making it output LOW on both Q and Q inverted, making them oscillate at the start until they stabilize at one state. Which bears the question why the manufacturer would suggest that you pull both pin 9 and 12 low for astable multivibrator free running mode?
Of course, I might be totally wrong on that one.
If one of your viewers had a genuine IC, is there someway to measure each pin for a value that can be compared to the ICs you have of questionable authenticity??
I have a working 4047. With the black lead on pin 7, Richard got a reading on pin 10, but no reading on pin 11, but I get the same reading on both pins. So a difference there.
Bad TI logo. 99% certain they are fake
some woman like the multivibrators..... ooh wait those are different things 🤣🤣