A 2x14 V transformer with the center tap at ground would give about +-18 V at the filter capacitors. With a small transformer and low load the voltage can be some 20 % higher. So about OK (with plenty of reserve for a lower mains) for the +-12 V regulators.
For T1 one one would have to choice of something like 24 V / 2 A or 12 V up to about 3.2 A DC (assuming a transformer rated for some 3.3 A AC).
If you will be testing the design on a breadboard, consider connecting R6 to the ORing node instead of directly to the output of the CV opamp. This idea suggested to me by Kleinstein greatly reduced the voltage overshoot in my PSU design whenever it transitioned from CC to CV mode.
With TO3 and essentially all TO220 transistors the case metal is connected to the collector of the transistor. If one needs isolation depends. Thermal past alone is not a vaild isolation.
For the 7812/7912/7805 it depends on the power loss if and how much heat sink is needed. With a low consumption for the regulator part there is a chance to get away without. One could still reserve space for a small heat sink. I would consider some 200 mW OK for a 78xx without a heat sink, so maybe 10 V and 20 mA. Chances are the LED display would need more power.
The diode bridges for the auxiliary power likely can get away without a heat sink.
enut11 posted a very simple but nice thermistor controlled on off fan switch but I worry about temp swing using an on/off type. I think I found a relatively simple variable fan circuit that is thermistor based and may help to keep a stable temp. I don't know till I try. Or I may just go with full time fan on and be done with it.I wanted to build something difficult and this definitely fits the bill so far.
Therm
Hi Therm
That 2 transistor fan controller from Reply #76 is a variable fan speed control. Ie, the hotter the heat-sink the faster the fan will spin. As the temperature rises the thermistor resistance drops which allows more base drive current for the transistors. The pot is just for adjusting the threshhold temperature. This could be around 35-40C, but your choice.
enut11
Hi Therm,
Did any documentation come with the meter?
It would be helpful if you can provide a closeup of the backside.
The two issues I identified with these cheap meters in my reply#36 were their burden voltage, and (on some meters) that you couldn't dial-down your PS below a minimum voltage (4.5V) without starving the meter for power. Fortunately, the burden voltage from the meters built-in (low-side) shunt can be removed by attaching the wiper and lower fixed contact of (10T) pot R37 to point B (vs. A) in the attached diagram (from rolycats link). And by providing the meter with its own FULLY ISOLATED supply, it will happily read 0V with R37 fully CCW.
Having two shunts in the circuit does introduce another voltage drop (probably by a few 100mAs) between unregulated to regulated sides, however, I think the simplicity of the meter installation makes up for that; ie. NOT having to configure the meter to use your existing shunt (R2), choosing a full-scale Vref, calculating dividers, and re-calibrating. And the bonus of eliminating R11, R12, R18, and R17. UNFORTUNATELY, by using this meter (with built-in shunt) you won't be able to set/view your current setting by pushing momentary SW1A. Instead, you'll have to short the outputs while adjusting R19.
These cheap Chinese meters are not based on the custom logic ICL7107 ADC but instead on a cheap ($1) STM8 MCU with 10bit ADC. It probably uses oversampling to get 4 extra bits to achieve 10,000 counts (at 2 Hz refresh).