Audio Research Amplifier Repairs

Audio Research SP-10PS Amplifier

This had the 47k 5W resistor replaced with a 100ohm one, which had blown the 7 Zeners 27V, replaced them but the HT was stuck at around 200 V. I put the valves on my tester (Knight 400) which gave them the okay, 2x 6L6 and a 12AT7 (ECC81). I found one of the 100 ohm grid resistors o\c and replaced the TL071 all to no avail. The regulator seemed to be acting strange, pointing to faulty valves. As I didn't have any spares I had to leave it un-repaired!