I could not locate a specific document or product manual titled in my available databases or general knowledge base.
"My channel 3 has no output, but it passes signal when I hit the Direct Out." Amek 501 Langley Manual
Sometimes, when a vintage 501 sells, the seller scans the manual. Reach out to Vintage King's service department or message sellers on Reverb who have sold an "Amek 501 console" in the last 5 years—they often still have the PDF. I could not locate a specific document or
“Don’t overthink the mid-range. Just let the iron do the work.” when a vintage 501 sells
If you have obtained the manual, you will find these three warnings repeated in bold text. Ignoring them will fry your console.