Technics SU-8600 Integrated Amplifier
Heres an interesting AU-8600 Integrated Amplifier by Technics which was a Panasonic house brand. Its a fairly large unit with some impressive features such as a nice enclosed multi-stepped attenuator, robust heavy shielding signal wiring and constant current feed dual FET amplifier gain stage based on a limiter and BJT circuit.
As usual I used some Panasonic FR/FC low impedance high temp capacitors along with Panasonic THA's in the filter, should note a surprise BP is in as well. There are some components to note; TR501/502 the regulator pair and the voltage regulating BJT are a 700BJT case with have poor endurance. These should be replaced with ksa1220/6909 and a ksc 2383. I replaced the general diodes for a more robust 1n4002. The relay was a standard MY-2 Omron which is a drop in replacement, along without he noted THA filter caps above, no pinout changes to worry about.
I used some nice Elna Silmic II's and FG's throughout the amplifier stage along with some WIMA MKS2 vie been using exclusively now for all low capacitance locations. I would like to add we zoo those 700# BJT's here again in the pre-driver pairs. I replaced them again with ksa1220/kscd2690A's respectively. Lots of folks have reported noise from these particular locations. I should add removing the heatsink ank to-3 output bank is easy. Putting the assembly back in is another story….This unit features biasing test pin locations which is always a plus.
The input/eq and separate tone control assemblies were recapped using Elna/FG's and more MKS2 films along with a ES BP. Note that one the input/eq PCB has a polar lytic between the pre out and ground tap, also the selector shaft needs to be remove to properly contort the board. I also ended up removing the entire front chassis assembly to angle the main PCB to an accessible point.
All in a very robust integrated unit, the silver by the way only came with a outer wood case, no metal enclosures except the pre shielding. The black variant sports a case and rack handles from what I am seeing.