My modifications made it work well and be much more reliable:

 

Thank you so much for posting these Audioguru.
What was the rationale for changing the V&A potentiometer values?
Actually to avoid myself asking you dumb questions, was there a particular forum thread where you narrated these developments?
73s Ted
2E0THH

 

I should add that I intend to limit the power to a few amps,
I have 2 transformers 24v AC and 18v AC. both are only capable of delivering a couple of amps.

 

The pots P1 and P2 have always been 10k ohms but 20k will also work fine. I added calibration trimpots.
I found the project with many errors 17 years ago at www.electronics-lab.com . I have not been there for years, they are completely different now. Today they have a new project that uses one of the bad kit copies from ebay. They reduced the transformer voltage to only 20VAC to prevent the old TL081 opamps from over-voltage. But there is no way it can produce its rated 24V at 3A. Its main filter capacitor is still way too small. It has the offset adjustment parts wrong as you discovered. I do not know if its opamps are fakes.

It was on the internet for years then it became a kit from a kit company in Greece and I found one (but I did not buy it) locally. Recently many of the Chinese companies copied the original defective kit.