Sir Clambake . . . . . . .
On your two . . . .LM324 . . .4 section operational amplifiers . . . . . being common as dirt / multi decade design workhorses . . . . flat pack I.C.'s that you identified . . . I would surmise that the one
near the "beeper" has two of its sections used for a window comparator, and the other two related to creating the beepers piezo drive signal.
Now, for the LM324 IC with the heavy YELLOW wire passing across it :
This 324 is close enough that it might be used a a variable oscillator followed by a pulse width modulator function related with the pots adjustment .
Evaluating that assumption would typically be requiring an oscilloscope savvy analysis . . . .OR . . .Mac Guyver'ing it by placing your DVM negative meter probe to ground
( any buss directly tied to pin 11 of the '324) and then MULTI twirl one lead of a .1 - - - - - thru a - - - - - - - 1 ufd poly/paper capacitor around the meters + probe and use the caps free lead to probe AC readings with .
Try probing pin 1 of the 324 while powered up and running the pot thru its extremes to confirm any AC voltage swing during that adjustment.
Then probe pin 7 for the same type of testing.
Then probe pin 8 for the same type of testing.
Then probe pin 14 for the same type of testing.
Finding voltage variance on those test points would tie that IC functioning to the pots adjustments . . . .and it is being the closest IC to the pot
You had not made any response in checking out the BLUE relays coil voltage.
Then . . . . . that might have been due to your not identifying its connections.
"Reading" as best as I can make out from the photo . . . . due to plated thru vias sometimes transfering connections to the other side of the board.
It is utilizing a SM1H-24v relay and I have placed one at the center of the photo for confirming its basing's contact terminals and coil layouts .
To the SPDT contacts I have assigned AC(armature common) and A1 is being its normally closed contact and the A2 as being its energized contact.
The coil is using assigned C1 and C2 designators. The GREEN path is an un-activated relay while the RED path is when its coil is energized.
So, if you look at the relays co-joining foil paths, the C1 connection passes up to be constantly connected to A1 terminal.
While the C2 terminal zags over and up to the top be constantly connected to A2 terminal.
So, overall, it looks like AC terminal is being the recipient of one or the other of the polaritys of the coil supply voltage.
As I am seeing it, the C1 terminal seems to be the negative or ground terminal while the C2 terminal is being the eventual recipient of an 24 Vdc.
I say eventual, because if you look at its foil's downward path, it initially connects to the first of a "scheiss pot" of 16 sequential series 68 ohm SM resistors
AND then it transitions to using nine 100 ohm resistors in series.
So in one relay position, all of that string could end up in parallel with the relay coil. BUT at that transition of 68's to 100's there must be a via that connects to circuitry at the other side of the board.
There is one GREEN ferrite coore with its heavy winding that connects to two of the HEAVY foil lands to the side of the the relay, with the copper wire seen on the one that is in the shape of a sideways numeral 1.
But that seems to be to far away as to be related. There is one white bisque 7 watt 4.7 ohm power resistor at the end of the relay and one electrolytic at the side of the relay near its coil which might be shunting it and
creating that engaged on off time constant that you are hearing . . . . .since I see no spike damping diode being used near the relay coil.
On the topic of toroids . . .specifically the YELLLOW cored one, I am seeing the output of the low voltage / high current power from the SMPS at the rear of the unit being looped thru it and it LOOKS that it is just one wire winding.
- Can you confirm that it is not having one wire looped thru it for a current transformer function?
If not, that cored unit will just be used for RFI suppression.
- Which then will take us back to the GREEN cored one . . . .is it just having a single winding on its core ?
I am trying to functionally account for the rather heavy gauge WHITE and BLACK wires that are routed towards the switch and then beside the LARGE raw DC filters.
Relating to post #52:
- Look at the mark up of the BLUE relay and note my assigned AC and then go right, just past theYELLOW case outline and tell me what the black device is? ? ?
It says 12VDC .40 amps
I think that you are just finding yourself a common brushless computer fan being used there.
Relating to post #55:
"I've decided to go with the switch shorted pot leg idea. I am going to try to ignore the minor sparking."
Combined with . . . .
"By the way, I checked that little sensing spark's voltage with my DMM -it was 3VAC *and* 54VDC -I don't know if that means dual voltage or my DMM is messed up..."
There is a series fed combination of high voltage and a BRUTE force variable DC voltage going to your electrode.
Your 54 Vdc seems right in range, within a particular positioning of the "power" control pot.
The 3VAC cold be in error due to the way some DVM's respond to a combined DC and AC voltage or the HV produce might be of such a narrow pulse width, that it
is responding with a decreased displayed value as compared to the meters EXPECTED sinusoidal waveform.
You will notice above, that I had you DC isolating your AC metering, for an expected symmetrical waveform (the oscillator portion) being in at least one part of that 324 circuitry.
A narrow pulsewidth waveform would give an erroneosly low reading in either situaton.
When you bring your "stick" in to your grounded work, the couple of KV's of high voltage initiate a small inter sparking, which creates an initial ionized path.
The 54 volts or so, at MULTI amp POWER capacity then sees that it NOW has a conductive path and it PUSHES in and . . .
. . . .
its ARC city ! . . . .with that initial sparking evolving into HOT plasma, until you pull the "stick" away.
Thassit . . . .
73's de Edd