i was thinking about the filter caps or the two resistors regulating the output (but those i just check them)

Other components shorted could make the output of the regulator appear lower, due to it being overloaded and unable to maintain regulation. If this is happening, the regulator will get physically hot rather quickly.

so now the fun part starts. try to find that darn component!

 

I'm back!

@thatoneguy was right, one of the 555 timer was shorted and was stressing the Vreg, after i changed it, i was getting 16V again at the vreg output.

I was checking again voltages and the cd40XX that drives the SCR is getting voltage at all the pins, between 10 and 16V in all of them, but the output is getting around 300mV, that's why the transistor in charge to drive the SCR gate is not getting triggered.
Still working on the diagram to see if that shed some light...

 

Ok, is the output supposed to be over 300mV?

Have you replaced the SCR or Transistor?

 

Ok, is the output supposed to be over 300mV?

i assume is suppose to be more than that, otherwise the transistor is not being triggered

Have you replaced the SCR or Transistor?

Transistor is new, SCR is tested fine

 

Can you get the voltages from a working unit, the transistor and output voltages/waveform?

If you short collector and emitter on the transistor while looking at the output, does the output switch on? (You Can short C-E, but not C-B on a transistor). What that does is essentially fake turning the transistor "on" to get an idea if what is after it works in a switching circuit.

 

Can you get the voltages from a working unit, the transistor and output voltages/waveform?

i know that would be great, but i dont want to take the risk of messing up the one working

If you short collector and emitter on the transistor while looking at the output, does the output switch on? (You Can short C-E, but not C-B on a transistor). What that does is essentially fake turning the transistor "on" to get an idea if what is after it works in a switching circuit.

i just did that, shorting E-C with a alligator clip and it beeps like something is shorting (the machine has a speaker that beeps at the frequency of the pulses) and the red led doesnt light up (so no pulses at the output)
PS: the red led works and the transistor is a 2N2219 NPN
partial diagram:
View attachment pemf2.pdf

 

I was looking at this thread for the first time to day. As I understand you still have some problems. I do not know if this has been pointed out before. To many postings to go through. But to me it look like one or both components pin in the red circle are not soldered properly

 

I was looking at this thread for the first time to day. As I understand you still have some problems. I do not know if this has been pointed out before. To many postings to go through. But to me it look like one or both components pin in the red circle are not soldered properly

good catch, but that picture was long ago, that was the first part i found bad, that was a zener i desolder and i was waiting for the replacement, it's not like that anymore
Thank you!

 

i tried lifting one leg of R13 and still low output at gate. i did the same with R9 and same result, and the speaker stopped working also. it looks like it's feed trough Base-emitter of the transistor???
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

 

Do those frequencies change if you adjust the frequency on the front panel dial (is that an option?). If so, then something is working to that point, follow the lines that pulse at the desired output frequency to the output, and maybe highlight it in paint.

 

Do those frequencies change if you adjust the frequency on the front panel dial (is that an option?). If so, then something is working to that point, follow the lines that pulse at the desired output frequency to the output, and maybe highlight it in paint.

frequency increase if I adjust Frequency knob. at lower setting it was 160Hz, next setting 320Hz, next 640 and ther higher one 1280Hz.
also checking voltages i was getting almost 4V at higher setting at output the but still 235 mV after the 2.7K resistor R9. i dont understand how that voltage is regulated.
the trace coming from the gate output pin1 splits to the right going to the base of the transistor and to the left to drive the LEd bar graph, which works perfectly.



i think i need to find out how that voltage is being regulated, i assume it would have to be higher in order to trigger the transistor.

 

frequency increase if I adjust Frequency knob. at lower setting it was 160Hz, next setting 320Hz, next 640 and ther higher one 1280Hz.
also checking voltages i was getting almost 4V at higher setting at output the but still 235 mV after the 2.7K resistor R9. i dont understand how that voltage is regulated.
the trace coming from the gate output pin1 splits to the right going to the base of the transistor and to the left to drive the LEd bar graph, which works perfectly.
View attachment 51855

View attachment 51856
i think i need to find out how that voltage is being regulated, i assume it would have to be higher in order to trigger the transistor.

The reading variance is due to the response of your DMM. A Scope would be needed to see the actual values, what you are seeing is what the meter is essentially guessing at for an average value (most are designed to show close to correct voltage on a 30Hz-120Hz sine wave), unless it is a Fluke meter, or similar quality, the readings are useful in knowing there IS an output, but useless for finding the actual output voltage.

 

i was testing voltage at collector to ground and shows 16VDc and frequency varies if I change the frequency knob at 160, 320, 640 and 1280Hz . if you check my diagram, i get voltage at 2 pins of Pulse transformer, the other is ground and the last one no voltage at all. maybe a bad pulse transformer?

 

Test the coils with the POWER OFF, in Resistance (Ω) Mode on the meter, and post the DC Resistance of both the primary and secondary of the transformer. I assumed it was OK since I mentioned this a few weeks ago on the last page.

The 16VDC is a Bias Voltage with the AC Signal "Riding" the DC Bias signal. Once passed through a capacitor or transformer, the bias will vanish, leaving an AC Signal.

 

Test the coils with the POWER OFF, in Resistance (Ω) Mode on the meter, and post the DC Resistance of both the primary and secondary of the transformer. I assumed it was OK since I mentioned this a few weeks ago on the last page.

The 16VDC is a Bias Voltage with the AC Signal "Riding" the DC Bias signal. Once passed through a capacitor or transformer, the bias will vanish, leaving an AC Signal.

I'm talking about the pulse transformer (the red box next to the choke) the toroidal transformer is fine.
Anyway, the problem that i have trying to test the pulse transformer is that i dont know the schematic, there is no info online. also there is a diode shorting two of the pins.
If the pins are numbered clockwise, and pin1 is left upper corner tere are the results:
1-2= 0 Ω
3-4= 2.6 Ω
2-3= 5.12kΩ
1-4= 5.12kΩ

 

If 1-2 has a diode, what is the resistance in the reverse direction?

 

If 1-2 has a diode, what is the resistance in the reverse direction?

The same.
also about that 16VDC at the collector the frequency changes with the frequency knob, but nothing changes if i play with the intensity knob.

 

Are pins 1-2 in series with either the Triac or transistor output? e.g. the high voltage on the other side of coil?

0 doesn't sound right, not both ways, that's a short, not a diode. Are they going to different tacks on the PCB or to the same one?

Desolder the trigger trans and see if there is a signal at transistor, and what the resistances on it are out of circuit. Do it carefully.

Trying to find a replacement will be interesting if it is the problem.

 

Desolder the trigger trans and see if there is a signal at transistor, and what the resistances on it are out of circuit. Do it carefully.

what do you mean trigger transistor?

Trying to find a replacement will be interesting if it is the problem.

i'm trying to get a hold of the manufacturer, icant find anything online

i have attached the diagram, the pulse transformer is inside the yellow box. you can see the diode in parallel with pin1 and 2 and the collector of the transitor going to pin1.
i have signal at 1,2, 3 is ground but not at 4

 

That's not good. what quality is your meter again? Are you checking the resistance in the low range, or in K/Meg or Continuity?

If the coil is actually shorted both ways, that means there isn't really a coil, but you'll need a more accurate resistance reading to tell the difference if it is a low resistance coil. The diode is to stop back EMF from coil inductance, which tells me the coil isn't a single turn.

Please make the schematic a bit larger, maybe double size, and label the VReg output pins.