sa-606 = sa-6700
This amp's power indicators and peak indicators are LEDS, and uses two 8v 55ma incandescent bulbs to illuminate the meters. They are part of a purpose built transistor regulator circuit. 50mA bulbs from dgwojo should work just fine. Substitutions with more current will be a PITA.
The manual is not helpful as to any of the bulb's dimensions. the ones of dgwojo's that I speak of are 4mm with bottom leads - not fuse types.
tx-606 = tx-6700
This is a different animal, it uses a LED power indicator (13v, 470 ohm series resistor), a LED stereo indicator(a strange little circuit),a 8v 100mA pointer bulb and two 8v 55mA bulbs, with all three directly connected across the 8v transformer winding - thus their current isn't critical.
The manual is not helpful as to any of the bulb's dimensions.