electromagnetic field therapy

[petit]

Re: electromagnetic field therapy

May be, it depends on how the 555 is set up to be, the one with 16V out put may not be setup as Oscillator. You can put your meter to AC mode and take the reading at the output pin of all 3 555 to see what you read.

I Changed that timer, still no difference, i'm getting 3V DC and 6V AC

[budm]

Re: electromagnetic field therapy

On all three 555's output pin?

[petit]

Re: electromagnetic field therapy

On all three 555's output pin?

no, i get 7V AC in the one next to the speaker and the one next to the green cap acts crazy, looks like that one is the oscillator.

[petit]

Re: electromagnetic field therapy

at this point should i recap the whole machine?
there is no that much left to replace...the only thing left besides the resistors is: three small can transistor,4 of those square black things, one 555 timer, the choke and the other brown box (pulse transformer i think)....

replace already: all the cd4000 two 555 timers,electrolitic filter caps, big metal can transistor, both tantalum caps, some diodes.

any idea?

[petit]

Re: electromagnetic field therapy

What do you guys think about the pulse transformer driven by the metal can transistor?that pulse transformer drives the SCR gate, and that SCR gate is not getting any voltage.
following the traces, i'm almost sure that the pulse transformer is getting voltage. do they usually get damaged?
any way to test it?

[budm]

Re: electromagnetic field therapy

You will need to find out how the primary is driven, may be by a transistor?

[petit]

Re: electromagnetic field therapy

You will need to find out how the primary is driven, may be by a transistor?

yeah, i think that can transistor is the one driving it.
that transistor was replaced, so it's fine.
can i check if that transistor is getting voltage without messing up anything?

[budm]

Re: electromagnetic field therapy

You should be able to check the Voltage at the Base and at the Collector, I believe the Base should be driven by the 555 to produce the pulse. Need to find out where the trace from the Base goes to.

[petit]

Re: electromagnetic field therapy

You should be able to check the Voltage at the Base and at the Collector, I believe the Base should be driven by the 555 to produce the pulse. Need to find out where the trace from the Base goes to.

Testing the transistor i'm not getting voltage at the base. the trace comes from that CMOS, (CD4068BE) left corner of picture pin1.
That chip is getting voltage at VDD and after that, i dont know what to do.
That chip is new
.

[petit]

Re: electromagnetic field therapy

Testing the transistor i'm not getting voltage at the base. the trace comes from that CMOS, (CD4068BE) left corner of picture pin1.
That chip is getting voltage at VDD and after that, i dont know what to do.
That chip is new
.

EDIT

yes, i'm getting voltage at the base, mV, because of the resistor 2.7K next to base. now i'm lost after the transistor. after that it goes to the pulse transformer.
any idea testing that pulse transformer??

[petit]

Re: electromagnetic field therapy

is this mess helpfull in any way tp see why i'm not getting signal at the scr gate?

[petit]

Re: electromagnetic field therapy

i'm been working making like a schematic over a pic of the PCB. let me know what you guys think!

Thank you

[budm]

Re: electromagnetic field therapy

Tracing out the board will be the best thing to do at this point.

[redwire]

Re: electromagnetic field therapy

If you take picture of both sides of the board, in Gimp or Photoshop mirror the PCB pic and then overlay on top of each other. Then it's easy to draw the schematic, and you don't have to keep flipping the PCB around and breaking wires.

[petit]

Re: electromagnetic field therapy

If you take picture of both sides of the board, in Gimp or Photoshop mirror the PCB pic and then overlay on top of each other. Then it's easy to draw the schematic, and you don't have to keep flipping the PCB around and breaking wires.

Thank you for the tip, i'll try that. do you know if those pulse transformer usually get damaged? because i'm getting signal at the transistor but not at the SCR, and the pulse transformer is the only thing in between!

[redwire]

Re: electromagnetic field therapy

Pulse transformers rarely die. You can check with an ohmmeter, a low reading across the primary and then the secondary windings. The (pulse-xfmr) transistor will need >650mV on its base before it turns on. If you are getting much less voltage, then the fault is probably upstream.
In your picture, there is a white teflon sleeve connecting a part. It's looks kind of crappy, is the lead connected, with no shorts?

[petit]

Re: electromagnetic field therapy

Pulse transformers rarely die. You can check with an ohmmeter, a low reading across the primary and then the secondary windings.

The (pulse-xfmr) transistor will need >650mV on its base before it turns on. If you are getting much less voltage, then the fault is probably upstream.

i'm getting 20 to 40 mV swinging at the base of the transistor, so there is a problem there. there is a resistor 2.7k in series with the base of the transistor, and the trace is coming directly from the output of the cd4068. that chip is putting 16V...

In your picture, there is a white teflon sleeve connecting a part. It's looks kind of crappy, is the lead connected, with no shorts?

you catch that one! that was me, i was desoldering that timer to put a socket and a new timer there and the trace around in the hole fell, so i had to put a crappy bridge there jumping from the leg of the 555, i dont know how to fix it better

[petit]

Re: electromagnetic field therapy

i have a better one here

[petit]

Re: electromagnetic field therapy

The (pulse-xfmr) transistor will need >650mV on its base before it turns on. If you are getting much less voltage, then the fault is probably upstream.

This right here shed some light on the problem, but what it can be??? there is a trace coming directly from the chip...there is just a 2.7k resistor in that path...

[budm]

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.