Sjöström Audio DIY forum

That's strange indeed. Here are the DC voltage measurements.

Rectified B+ (before even connecting the SSR01): 30VDC
Input voltage on the SSR01 when connected to B+ but with no load on the output: 18.3V
Input voltage on the SSR01 when connected to B+ with a 100R load: 7.3V

The input voltage is? Something isn't right here.

Output = 5.2
Q2 = 0.9
IC = 1.67

= 7.77 V is that what you have as input voltage? In order to work properly you must have 18V in min.

With a 100 ohm resistor, I get a 0.9V difference on Q2 (pins 2 and 3), and a 1.67V difference on IC1 (LM317, pins 2 and 3). Thanks again.

I'll suggest that you take three 1N4148 in series instead or put the led in a shrink tube or paint it black. If you increase the H1 voltage, then the drop out voltage will increase and then you'll need to adjust the voltage of the IC1.

When you load with 100 ohm, what is the voltage between emitter and collector of Q2? Voltage between in and out of IC1?

I've taken some measurements and with a 100 Ohm resistor, the voltage drops from 12.3V to 5.2. With a 1k resistor, then there is no drop.

I'll suggest that you try with 120 ohm or something. This would create 100 mA.

If the regulator works you should have a voltage drop of a few millivolts only and the voltage at pin 2 and 3 on the opamp should be within 1-2 mV, and that is 6.25V if the output voltage is 12.5 V.

Well, I don't know how much current can I draw before voltage drops. What would be the best way to actually measure this (variable CCS, resistor, ... )?. Thanks.

How much current are you able to take out before you'll get a voltage drop?

I'll recommend that you connect to the unregulated voltage in order to avoid unnecessary heat in the voltage regulator. Adjust the resistor value so the light is enough.