Assembling the Automatic Transmission Solenoid Tester:
The air source at the inlet of the unit can be either an industrial air line or an air compressor with a pressure of at least 65 psi (approximately 4.5 atmospheres or 4.5 bar).
In my case, I used a quiet HYUNDAI HYC-1406S compressor. This compressor allowed me to repair and test solenoids in a city apartment in a 16-storey building.
Next, a pressure regulator is installed that reduces the pressure to 70 psi. You can use this one. I have a regular regulator with a pressure gauge installed on the compressor. You can buy it on aliexpress or on ebay for $ 18.
Since the high-precision pressure regulator has a rather significant air leak (leakage is necessary for the normal operation of the regulator), a conventional valve is installed between the standard pressure regulator and the outflow regulator for convenience. It is necessary so that the regulator does not release pressure between work and the compressor does not work idle. Sold on aliexpress or ebay. Average cost is $5.
Next, a precision (high-precision) pressure regulator is installed. There are many expensive precision pressure regulators from well-known companies for $ 300 or more, but I can advise you to buy such a regulator - IR2020-02BG worth $ 100. You can buy it on aliexpress and ebay. I have it installed VEX-1330 bought for $30 at a flea market.
High-precision pressure regulators can have inlets and outlets with both ½ and ¼ inch threads! Ask the seller and get yourself a fitting or adapter for the desired diameter! The pressure gauge outlet can be plugged as unnecessary.
Next comes the standard $5 quick-release flexible hose adapter. You can buy it on aliexpress or ebee.
Next, you need a flexible hose about 3 meters long, costing $ 5.
To power the device, it is VERY IMPORTANT to have a powerful regulated power supply, as a deviation of only 0.5 volts from 12 volts under load gives a floating result.
I use this $10 power supply.
BE SURE TO ADJUST AND TEST THE POWER SUPPLY!
IT IS REQUIRED TO HAVE STRICTLY 12 VOLTS ON THE POWER SUPPLY!
The permissible difference in power supply under load and without plus or minus 0.5 volts (that is, from 11.5 to 12.5 volts. There is an adjusting resistor on the power supply to fine-tune the voltage. Try to adjust as accurately as possible to 12.0 volts!
After adjusting 12.0, you must connect a 4-6 ohm solenoid or resistor and check the deviation of the reference voltage of 12.0 volts. If the deviation is more than 1 volt, you must change the power supply.