electromagnetic field therapy

[petit]

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.

i was thinking about the posibility of a shorted component stressing the output of the IC. i dont know if that is posible.
i the same thing happened to the vreg, a IC was shorted and it was stressing the Vreg to the point that i was getting just 2V at the output, after i replaced that IC the vreg went back to 16V

[budm]

Re: electromagnetic field therapy

The load on the output of the 8-input AND gate is only about 2700 Ohms that you have verified.

[petit]

Re: electromagnetic field therapy

The load on the output of the 8-input AND gate is only about 2700 Ohms that you have verified.

Yeah, there is a 2.7K resistor between the output pin and the base of the transistor, but i also noticed that before the resistor, that trace splits and goes to the left side of the board to feed a 555 and another small chip, that i think is in charge of the led strip under the knobs.

[budm]

Re: electromagnetic field therapy

That trace must be feeding some components, what ever they are, lift one of the legs up so the output of the AND gate will no longer drive it, you will have draw up that circuits to see how it is hooked up.

[petit]

Re: electromagnetic field therapy

That trace must be feeding some components, what ever they are, lift one of the legs up so the output of the AND gate will no longer drive it, you will have draw up that circuits to see how it is hooked up.

i'm trying to draw that part of the circuit right now.
the first thing i find when that trace split to the left is a 27k resistor, so if i lift that resistor and the gate wont longer drive that part of the circuit, it would be safe to that? i dont want to burn anything else!

[budm]

Re: electromagnetic field therapy

You will not be driving anything, that 27K load should not cause the output of the AND gate to be low, way too high load resistance to cause that problem.

[petit]

Re: electromagnetic field therapy

You will not be driving anything, that 27K load should not cause the output of the AND gate to be low, way too high load resistance to cause that problem.

ok, let me lift that resistor to see what happens

[petit]

Re: electromagnetic field therapy

ok, let me lift that resistor to see what happens

still no output, output gate still low

[budm]

Re: electromagnetic field therapy

Something is being overlooked on this simple AND gate, are you sure that ALL the input pins are HI, what is the reading on each input pins?

[redwire]

Re: electromagnetic field therapy

Hey one thing I noticed - some CD4068's do not have pin 1 connected. They are only a NAND gate without the dual (NAND/AND) outputs. Check the exact part data sheet.

[petit]

Re: electromagnetic field therapy

Hey one thing I noticed - some CD4068's do not have pin 1 connected. They are only a NAND gate without the dual (NAND/AND) outputs. Check the exact part data sheet.

Hi!
in this one pin1 is AND (the one in use) and pin 13 is NAND (not in use). i'm getting between 10 and 16V at all of the inputs

[petit]

Re: electromagnetic field therapy

working on the schematic
pemf2.pdf

[petit]

Re: electromagnetic field therapy

i just short the emitter and collector of the transistor, that would be like turning the transitor and the beep stutters.
i corrected the diagram, the transistor is npn, i had it as pnp
pemf2.pdf

[petit]

Re: electromagnetic field therapy

i lifted the resistor going to the base of the transistor and the speaker turned off. still getting around 300mV. it looks like that transistor also drives the speaker, but i get lost looking at the schematic.

These are the values at the CD4068:
Vdd: 15.62
pin1: 362mV pulsing 176Hz
pin2: estable 10.16V
pin3:6.67-8.59V pulsating same frecuency as beeping
pin4: 5.59-9 pulsing 7.5Hz
pin5: 12.28 estable 60hz
pin6; nc
pin7:Vss
pin8:nc
pin9:7.76 estable 30Hz
pin10: this one acts crazy between 1-5-14-and OL, 3.747hZ
pin11: 15.54V estable
pin12:15.59 estable

[petit]

Re: electromagnetic field therapy

i just short the emitter and collector of the transistor, that would be like turning the transitor and the beep stutters.
i corrected the diagram, the transistor is npn, i had it as pnp
[ATTACH]57419[/ATTACH]

any idea why the machine sound like there is a short somewhere when I short collector and emitter of the transitor driving the SCR?

[redwire]

Re: electromagnetic field therapy

The SCR gets a fast pulse to turn it on. So the transistor driving the pulse transfomer only turns on for little blips. If you short the transistor C-E the pulse transformer gets too much power and overloads the power supply and the beeper stutters.
Do you get any signal between A-K on the SCR?
Does the LED bar graph do anything?

Remember the pulse is fast, so your multimeter will not see all of it.
I think it's best to finish the schematic, then it is much easier to troubleshoot.

[petit]

Re: electromagnetic field therapy

The SCR gets a fast pulse to turn it on. So the transistor driving the pulse transfomer only turns on for little blips. If you short the transistor C-E the pulse transformer gets too much power and overloads the power supply and the beeper stutters.

when i was shorting C-E i was expecting at least get the red led ON for a little showing output signal but nothing happened

Do you get any signal between A-K on the SCR?

nothing there

Does the LED bar graph do anything?

LEd bar graph works perfect

i really dont understand how that transistor is working, i though it's supposed to drive the pulse transformer???? but is the one driving the speaker trough base-emitter


pemf2.pdf

all the output side is done. i'm not sure about the choke pins, but everything else is fine

[petit]

Re: electromagnetic field therapy

this morning i as checking frequency and voltage at pin1 of the AND gate.
The frequency increase if I adjust the frequency knob.
at lower setting it was 160Hz, next setting 320Hz, next 640 and at the higher setting 1280Hz.
also checking voltages i was getting almost 4V at higher setting at pin1, but still mV after the 2.7K resistor R9.

[budm]

Re: electromagnetic field therapy

The output at pin 1 AC pulse which is now make sense since some of the input pins are pulses not steady DC. The pulse at the other end of the resistor will be about 0.6~0.7V maximum bude to Base-Emitter junction voltage. If you look at the Base-Emitter voltage, you will see 0.6~0.7v pulse.

[petit]

Re: electromagnetic field therapy

If you look at the Base-Emitter voltage, you will see 0.6~0.7v pulse.

I wish i was getting that at the base! at full power setting i'm getting 234mV after the resistor, not enough to trigger.
i think i dont understand how that gate work. i tough i was supposed to get full voltage at pin 1 when all of the inputs are HI???
how is that outout voltage being regulated?
are the inputs capable to regulate the output pin?