I got a 22rh580 integrated amplifier from Charles yesterday: (thank you very much!)
(web pic, not mine, which needs washing still)
One of the 4 output transistors is missing (others might be dead?) , but Mantech has NTE equivalents so not a crisis.
The ODDITY is this: the RIAA equalisation is built into the amplifier permanently, and the tuner and tape inputs are put through a reverse RIAA network prior to swiching. Nuts! Loudness, as you'll see below, is always 'on'.
(I got the matching turntable too)

(web pic, not mine, which needs washing still)
One of the 4 output transistors is missing (others might be dead?) , but Mantech has NTE equivalents so not a crisis.
The ODDITY is this: the RIAA equalisation is built into the amplifier permanently, and the tuner and tape inputs are put through a reverse RIAA network prior to swiching. Nuts! Loudness, as you'll see below, is always 'on'.

(I got the matching turntable too)