ZD-8915 (SS-331) conversion from 18V to 24V

[Hardlife]

Hi,

i have same circuit like User Spawn...
(newer version power supply (ZD150-PQ32/15) - still 18V)

Because i am not a pro  - can smoebody please help me to identify the right resistor for manipulation?
@cybermaus ?

I attached better pics...
(R21 and R22 = 472)

Thank you,
Hardlife

[cybermaus]

I've been staring at it for a while, and I think I agree with @shawn: R20 which needs a parallel resistor on it, the value is 2K4 and I think it needs a 6K8 resistor parallel on it for +/-24V

Or alternately, replace the entire R20 with1 1K8 resistor (or 182 in numeric)

Mind you, its been a long time ago, I barely understand what I did back then, and most importantly, I cannot measure any if the lines are connected to the rest of the board I think they are.
I am basically just trying to map the old to the new from the picture, and to be honest, there is one resistor too many.
Maybe for safety, you can first put a parallel 22K resistor to it or so, and see if the voltage rises to 20V

[HumbleDeer]

The universal input supply shouldn't have any trouble running from 110v. It's a flyback, so it's built to be fairly proactive in compensating for loading or duty cycle requirements. Furthermore, the universal power supply models are actually rated for 110v, so it would be a grave oversight to have it not actually work properly.

Mind you again, changing the output to 24v will increase the power draw quite a bit. A resistive element doesn't scale its current draw back in response to a higher voltage. You may need to implement an inhibit signal for the heater that pulls it down/off when the pump runs.

[leohobb]

Hey thanks i advance for the work you have done. On my zd 8915 with no sleep function the psu is ZD-P150 V 2.0. It output as u say 18 volts output. my fan witch voltage is no problem for since my fan is rated at 36 volt, is moved to the top  with one bolt and a stand of 5mm on top of the supply shield cut a hole for fre air flow into the supply, stand of make it blow air direct on the sides of pump motor.also drilled some vent holes on the side where the air can get out. One thing would like to know, with the parallel resistor to get 23.5 volt. the added one 68K? and on the board a smd 24 k ohm?. would not the power take the path of lowest resistance? in other word would not most power go true the smd one? it cant be much current anyway. i am about to order lots of components from digikey for div project i have cooking. Thanks again.

[cybermaus]

"would not the power take the path of lowest resistance? in other word would not most power go true the smd one?"

If nothing else, electronics is about maths. Every variable weighs in on the result; even if most current will flow through the lowest resistor, both resistors weigh in on the total result.
So I suggest you start with some videos on resistor calculations.

So as to the "power take the path of lowest resistance", that is a common saying, but not strictly correct.
Current takes all available paths in parallel. Again, watch some videos on resistor calculations.



As to "ordering a bunch of stuff from digikey"
I suspect you may be soewhat at the beginning of this skil/hobby, which if fine, everyone was at some point, (in fact, still a noob myself, on account of only playing with it every so often) but unless if you have money to spare,  don't spend too much on expensive individual components from an expensive supplier if you are not at that skil-point yet. Find some maker stores to buy some kits.

[HumbleDeer]

To corroborate and elaborate upon the reply given by Cybermaus:

The electricity does take the path of lowest resistance, because that's a fairly arbitrary figure of speech

In reality, the electricity flows through all paths, but when not all of them are equal resistance, one path will be preferred. The electricity does not, however, decide to not flow through the higehr resistance path at all. After all, that would imply electricity has sentience of some kind.

Concluding this, I can solidly assert that electricity takes every path at all times, and the amount of current that flows over a specific path is directly proportional to its resistance. The "amount" relative to the other parts will as such be proportional to the other parts. Read: two paths of 1K ohms are both equal percentages of the total resistance (500 ohms). That means the current flow through both resistors will consequently be proportional to that, i.e. half through one, half through the other.