electromagnetic field therapy

[petit]

Re: electromagnetic field therapy

That is the typical way of interface the output of the Logic IC to drive the transistor. cd4068 is an 8-input NAND gate, you need to download the spec sheet and look at all 8 input pins to see what you have and how all 8 inputs are connected to.

i'm pretty sure all imputs are getting signal, because the is output at pin 1 (AND)

[budm]

Re: electromagnetic field therapy

To have the output at ligic HI, it only needs to have one input at LO for the output pin to be HI, if ALL inputs are HI, the output will be LO. So what reading do you get at all 8 inputs?

[petit]

Re: electromagnetic field therapy

To have the output at ligic HI, it only needs to have one input at LO for the output pin to be HI, if ALL inputs are HI, the output will be LO. So what reading do you get at all 8 inputs?

i havent check all imputs, i just check the output. that CMOS it has two output, one is NAND, and the other AND, and the circuit is using the pin 1 (AND). i hope it make sense

[budm]

Re: electromagnetic field therapy

Oh OK, I miss the output pin the circuit is using, then all the inputs have to be HI then to have HI on output pin 1. I believe one of the input may have input pulse so the out put wll be pulsing for driving the transistor, the output can then be turn off by take one of the inout pin to LO to turn off the drive.

[petit]

Re: electromagnetic field therapy

Oh OK, I miss the output pin the circuit is using, then all the inputs have to be HI then to have HI on output pin 1. I believe one of the input may have input pulse so the out put wll be pulsing for driving the transistor, the output can then be turn off by take one of the inout pin to LO to turn off the drive.

yes, but the problem is there is not enough voltage at the base of that transitor to turn on. there is voltage coming out of pin1 but not enough voltage between base and emitter to turn on.

[budm]

Re: electromagnetic field therapy

That is the probelm, pin one should be close to 15V when all input are high, the voltage after the resistor will be about 0.6~0.7V for the Vbe to turn on the transistor.
If you are not getting 15V at pin 1 and ALL input are high (> 7V, has to be more than half of the VCC for the IC to be consided as HI). So how high is the voltage at all the inputs.

[petit]

Re: electromagnetic field therapy

That is the probelm, pin one should be close to 15V when all input are high, the voltage after the resistor will be about 0.6~0.7V for the Vbe to turn on the transistor.
If you are not getting 15V at pin 1 and ALL input are high (> 7V, has to be more than half of the VCC for the IC to be consided as HI). So how high is the voltage at all the inputs.

i dont remember right now how much i'm getting at pin1, but after the resistor i'm just getting between 20 and 40mV

[budm]

Re: electromagnetic field therapy

I the think the output is sitting at logic LO right now at pin 1, that is why it is important for you to look at all the input pins voltage.

[petit]

Re: electromagnetic field therapy

I the think the output is sitting at logic LO right now at pin 1, that is why it is important for you to look at all the input pins voltage.

yes, think i have to look carefully at all the inputs, because maybe that where the problem is coming from. i'm working on the diagram right now, maybe that helps a little.

[Jim@HiTek]

Re: electromagnetic field therapy

I didn't read every page of this thread so I don't know if anyone else suggested this for future work. When I have a product that blows ONE fuse at turn on, I grab my light bulb socket and clip it across the fuse holder. Then I put in a 40 to 100W bulb, depending on fuse size (but never more the 100W). Turn on the device and I have extra light while I DVM around the circuit. I also have soldered light bulb socket wires to a blown fuse so I can just snap it into the fuse socket. Same goes for DC, using a large 12V automotive bulb with the two filaments leads soldered together. The lowest voltage point is near the short.

[petit]

Re: electromagnetic field therapy

This thing is driving me crazy!
the other day somebody told me to check all the voltages starting at the Vreg to trace the signal, so i started testing voltages at the Vreg, probe slipped, a little bit of smell, and the machine stopped working almost completely, just a little bit of sound from the coil and the power Led barely on. so i thought the Vreg was blown, i check resistance between pins and i was getting different value that before between ground and pin 2 i think. so i ordered (expensive part $9) i replaced and still the same, and i think it has blown too! i'm getting 24V in and 2V out, also the first zener in the string is blown too. anybody know what can be causing this? it may be this first zener?
i have drawn the imput part of the diagram, maybe that helps

[redwire]

Re: electromagnetic field therapy

Ok, you need to get better test leads, sharper tips, put tape/heatshrink on them, or something.
Assume things got over-voltaged again, so any of the IC's could be blown or a cap shorted.
If you only get 2V out and no chip is getting hot, the Vreg is blown.
If the Vreg+zeners are getting hot, they could be stressed giving power to a shorted IC. Pull the IC's out of the sockets and see if the rail voltage comes up.
For the Vreg, you could ditch the zener diodes, change the 220uF's to 50V parts, and substitute in a LM317T for $0.75

[petit]

Re: electromagnetic field therapy

Ok, you need to get better test leads, sharper tips, put tape/heatshrink on them, or something.
Assume things got over-voltaged again, so any of the IC's could be blown or a cap shorted.
If you only get 2V out and no chip is getting hot, the Vreg is blown.
If the Vreg+zeners are getting hot, they could be stressed giving power to a shorted IC. Pull the IC's out of the sockets and see if the rail voltage comes up.
For the Vreg, you could ditch the zener diodes, change the 220uF's to 50V parts, and substitute in a LM317T for $0.75

thank you! you always give great advice!
i did changed the Vreg, because i was giving me different measure than before, so i assumed that was the problem, but it wasnt.
i think you're right, one of the IC has to be shorted, i'm gonna check those but first i have to replace that zener with a 5W one.
the Vreg that i put there is a NTE953. that's the one the gave me as a cross reference for the one it had.
so you have any idea why that transistor is just getting 20mV??? i'm gonna post the diagram as soon as i have it complete.
thanks a lot!

[petit]

Re: electromagnetic field therapy

Ok, you need to get better test leads, sharper tips, put tape/heatshrink on them, or something.
Assume things got over-voltaged again, so any of the IC's could be blown or a cap shorted.
If you only get 2V out and no chip is getting hot, the Vreg is blown.
If the Vreg+zeners are getting hot, they could be stressed giving power to a shorted IC. Pull the IC's out of the sockets and see if the rail voltage comes up.

i pull all the IC's out and found the bad one! now it's "working" again.

i was testing yesterday the odd black capacitors and one of them was giving me 100nF and is supposed to be 63nF. could that be causing the initial problem??

[petit]

Re: electromagnetic field therapy

I the think the output is sitting at logic LO right now at pin 1, that is why it is important for you to look at all the input pins voltage.

Hi!

all input pins are getting signal, around 16V, all of them. and i'm getting like 300 mV at pin 1 (output). maybe there is something stressing the chip, that's why i'm getting just mV at the output?????

[budm]

Re: electromagnetic field therapy

If all the input to the AND gate are high and the output is still LO, then lift one leg of that resistor that feeds the Base of the transistor, if it is still LO, then the AND gate IC is bad.

[petit]

Re: electromagnetic field therapy

If all the input to the AND gate are high and the output is still LO, then lift one leg of that resistor that feeds the Base of the transistor, if it is still LO, then the AND gate IC is bad.

good idea! thank you.
the AND gate shouldn't be bad, it's new.

[budm]

Re: electromagnetic field therapy

There is not much to the AND Gate IC, if all inputs are HIGH, the output has to be HIGH also, there is nothing else to cause it to be stuck at LO output.

[petit]

Re: electromagnetic field therapy

There is not much to the AND Gate IC, if all inputs are HIGH, the output has to be HIGH also, there is nothing else to cause it to be stuck at LO output.

yeah, you're right, but what i dont understand why the output voltage is so low that is not able to trigger the Transistor

[budm]

Re: electromagnetic field therapy

If the output did not go high (close to the VCC level of the IC), then that IC has to be bad, the out put of the IC should be able to easily drive 2000 Ohms load without any problem at all.