Great work. When looking at these voltages I need to always know
what ground source you are referencing.
Ed wrote (enclosed in " " :
" Pin #4 53V with the meter set on AC and 24 V with the
meter set to DC. (I got the same results testing Fuse F1)"
I can't explain this. Where you using pin 1 as the ground for these
measurements? In fairness the only source I have for pin 4 being
220 VAC is from Dessalator (a notoriously unreliable source of
informatiion on this subject), as I have not measured or traced
those wires myself. To clear this up, perhaps you would do the
following and let me know what you find:
1. unplug plug 1 (P1)
2. with the 220 VAC breaker set and the 24 VDC panel switch ON
3. measure the voltage (both DC and AC) between pin 1 and pin 4
4. and (with power off) trace the red wire from pin 4 to see where
it goes (I can't make out its origin from the photos I have here.
"After a couple of minutes, Pin #5 thru Pin #11 all showed 24V DC –
did not test when this happened timewise. "
This would be appropriate as this essentiallly provides "activating"
24 VDC power (and return) to the following:
1, hi pressure pump relay,
2, low pressure pump relay, and
3. bypass solenoid.
The control side (i.e. sinking pins 7, 9, & 11 to ground) is controlled
through relays RY1, RY2, & RY3.
Furthermore this seems to imply that the logic board timer circuit
and some of the other ICs are functioning properly.
" I tested the pins on T1 and T2. with fuses to the "top":
T1 left pin 21.8V center pin ~ 0 right pin 23.5V
(should be ~ 12V?)"
Again, please verify what you were using as the ground for your
multi-meter when making these measurements. The right pin
should be 12 VDC, the center pin is ground (0 volts DC)), and the
left pin is the input from the full bridge rectifier/capacitor C1
combination. It is dependant on the input AC voltage on pin 4
(hence my need to know that voltage accurately). It may be that
T1 is shorted ?????, or the rectifier is gone????? and this is the cause
of your failure(s)?????? That would be a fairly logical failure mode.
" T2 left pin 21.6V center pin ~ 0 right pin 5.6V
This seems correct except I would have expected a 12 VDC voltage
on the left pin. The approx 5 VDC output voltage is appropriate,
and is what is fed to all the ICs and is why the green logic board
LED is appropriately illuminated and your logic board timer is working.
" I next disconnected the Plug#1 and tested between pin #1 and
pin #5. It showed 53V with the meter set on AC and 24 V with the
meter set to DC but only with the rotary switch turned to "ON". With
just the 220V breaker, there was no voltage here."
From this I believe that the 53 VAC you are seeing is an erronious
characteristic of your digital voltmeter when looking at DC voltages
OR that there is a failure mode that is allowing AC to bleed on to the
To trouble shoot this, I would:
1. with P1 plugged into the logic board
2. measure DC voltage between pins 1 and 4, and between pins 1 & 5
3. do this measurement in each of two configurations, with:
first: with the 220 VAC breaker set on ONLY, (rotary switch off).
second: 220 VAC breaker OFF and only the rotary panel switch on.
"Next I jumpered pin #5 to pin #8 and pin #1 to pin #9. The low
pressure pump came on and ran normally."
Great, that is as it should be. Jumpering pin 5 to 8 provides 24 VDC
to the low pressure pump relay, and jumpering pin 1 to pin 9 provides
a ground return for the relay, thereby achieving what RY1 does, that
is activating thelow pressure pump control relay (the 220 VAC control
So the manual work around is to have three single pole single
throw switchs. One switch each on pins 7, 9, and 11 with one pole
of each switch to each of those pins and the other pole going to
ground (i.e. pin 1). You then manually throw switch 1, activating
the low pressure pump, wait a bit, then throw switch 2, activating
the high pressure pump, then dial up the pressure until product
water is made, and finally when your electronic EC meter shows
you have truely good product water, you throw switch number three,
diverting the product water to your fresh water tanks. Then, if your
EC meter alarm sounds due to a failure resulting in the production
of poor quality water you turn off switch three and proceed to shut
down the system to make repairs. This is the "logic" that should
have been part of this board, but was not.
"406 KA7812" so it looks like the correct part"
I have confirmed that the output of T1 (aka Motorola 7812 or KA7812)
should be 12 VDC.
"BTW, the high pressure sensor switch was "open".
Thanks Ed. That confirms what I was theorizing.
"It shuts down the system at 68/70 bars."
That is between 986 and 1015 psi.