A Model Number may help others help you.
Model Number Locator

Here are your parts
Replacement parts for General Electric PSF26NGPABB Refrigerator | AppliancePartsPros.com
Control Board is Item 801 in Section 2

I assume you have already checked the heater and the defrost thermostat

I would remove the evaporator cover and check the heater should be around 20 ohms.
Also check the defrost thermostat should be 0 ohms when frozen. Note that it opens just above freezing so it must be frozen when you check it. Sometimes you can see it is shot if it is bulged out.

If both are OK then odds are it is the board.

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.

There is a good STICKY at the start of this forum about it's use.