I'll start off with the MAIN amp board:
The transistors first:
The schematic lists
Qe1-Qe4 as
2SC693U(E or F), but this unit has
2SC458 transistors installed in those locations, so I'll put in
KSC1845F.
Qe5,Qe6 are listed as
2SC627 in the schematic, but I can't read the label on these. The datasheet for 2SC627 is typical and boring until you reach the hFE of "360 minimum".
2SC627 NPN CBO=200 CEO=200 IC=100mA Pd=700mW fT=20MHz
hFE=360
So, these will have to be high output and it took a thorough run through
alltransistors to find devices that matched and Mouser to find one that was available and matched or exceeded. I'm going to try
ZTX696B instead of a Darlington since I really don'[t know enough about them to select and replace them confidently.
Qe7,Qe8 are listed on the schematic as
2SC960(I, L or M) and my unit has
2SC484Y installed there. These are complemented by the 2SA484Y in Qe9,Qe10, so a little extra care for this replacement.
2SC484Y TO-39 NPN CBO=150 CEO=110 Ueb=5V IC=1.5A Pd=800mW fT=10MHz hFE=30
KSC2073 will handle those needs well and it has a complement of KSA940, so KSC2073/KSA940 will be the ones for these.
As stated above,
Qe9,Qe10 is marked as
2SA607 on the schematic, but my unit has
2SA484Y in those positions. As stated above KSC2073/KSA940 is a complemetary pair that matches these parameters, so
KSA940 is what I'll use for Qe9,Qe10.
Qe11 has a
2SC373 on the schematic, but a
2SC984 on the actual board.
2SC984 TO-1 NPN CEO=50 CBO=50 IC=500mA Pd=350mW fT=100MHz hFE=30/300
Either KSC2690A or KSC2383 should work fine in the Qe11 position.
The strange gold-legged black-capped transistors at
Qe12,Qe13 are
2SC715E
2SC715E TO-92 NPN CBO=40 Ved=5V IC=200mA Pd=125mW fT=100MHz hFE=80
It looks like
KSC2383O will do fine here.
Lastly,
Qe14 is a
2SC734Y
2SC734Y TO-92 NPN CBO=70 CEO=50 Ueb=5V IC=150mA Pd=300mW fT=75MHz hFE=120
And I think KSC2383O will do fine here, too.
There are only two sets of diodes actually on the board, so they are easy:
De1,De2 are
1N60 Germanium diodes, so I'll replace them with NOS
1N60 or
1N60P diodes
1N60 Germanium glass diode Vrrm=40V If=30mA Ifsm=150mA
De3-De5 are strange-looking twinkie-shaped devices that the schematic calls out as
SM-150-S. I couldn't find specs exactly for the SM-150-S, but I found several places where SM-150-xx were discussed and it appears these are simple 100 V 1A diodes. If anyone knows differently, please let me know. If that is correct, then they can be replaced with
1N4002, but I like the ultra fast soft recovery
UF4002 better.
The capacitors are almost all electrolytics, so the replacements are mostly easy: bump up the voltage so the replacements are operating at 60-70% rated voltage, use nothing lower than 35 V (where possible), use film caps (for zero leakage) where possible (4.7 uF or lower) or low-leakage caps (Nichicon KL series) for everything else.
- Ce1,Ce2 1 uF 50 V --> UKL2A010KDD 1 uF 100 V (Mouser doesn't even stock the 50 V version anymore) or ECQ-E1105KF3 (much larger film cap, but it has no leakage, this one is the smallest I can find, and it will fit... it'll just be ugly)
- Ce10,Ce29 47 uF 3.15 V --> UKL1V470KPDANA 47 uF 35 V
- Ce11,Ce12 100 uF 50 V--> UKL2A101KHD 100 uF 100 V
- Ce13 220 uF 25 V--> UKL1V221KPD 220 uF 35 V
- Ce15 47 uF 100 V Axial --> TVX2C470MCD 47 uF 160 V Axial
- Ce3,Ce4,Ce14 100 uF 3.15 V --> UKL1V101MPDANA 100 uF 35 V
- Ce5,Ce6 33 uF 16 V --> UKL1E330MEDANA 33 uF 25 V
I'm crazy, so I'll be replacing the one ceramic cap while I'm in there
- Ce7,Ce8 220 pF --> FK28C0G2E221J 220 pF 250 V C0G (NP0)
I'll probably replace all the resistors on this board with metal film ones, but I don't want a bunch of "hey, why would you do that" comments just because I'm OCD and have lots of spares from mistaken orders, so I'll just skip putting those in here.
There are two trimpots on this board, so I'll replace them instead of rolling the dice and having them blow a transistor or more:
VRe1,VRe2 are three-legged, single-turn 10K trimpots so they'll be replaced with 3309W-1-103
This board leads directly to the output transistors and their resistors on the heatsink, so I'll cover those while I'm at it:
The output transistors
Q1-Q4 are marked as
2SC1115 on the schematic, but
2SC898 are installed instead.
2SC1115 TO-3 NPN CBO=140 CEO=80 Ueb=5V IC=10A Pd=100W fT=10MHz hFE=30-150
MJ21194G will be a fine replacement for these output transistors.
Power resistors at
R171,R172,R271,R272 and
R173,R273 may have been stressed, so they'll get updates, too.
- R171,R172,R271,R272 0.47 R 2-3 W --> CPF3R47000JNB14 0.47 R 3 W 5%
- R173,R273 4.7 R 2-3 W --> CPF34R7000FKB14 4.7 R 3 W 5%
The output in the KR-6160 is cap-coupled, so C171,C271 are huge terminal-lead caps installed up top, but I'll cover them here.
C171,C271 output-coupling caps handle the amplified signal just before it goes to the speakers, so these will need to be big (to avoid low end rolloff) and great quality (low or no leakage). Sadly, the KL series doesn't cover this much capacitance at this voltage (need 63 V minimum), so I have to look elsewhere. Nichicon makes plenty of snap-in and leaded caps in this size, so I'll choose some options that claim better audio performance but are roughly the same price as non-marketing-crap ones.
C171,C271 2200 uF 63 V --> UKW2A222MRD or LKG1K222MESAAK 2200 uF 100 V
(If Nichicon made ones that had skull tattoos on the side or little glasses of Japanese bourbon, I'd put those in there instead since they'd be "better audio quality"
)
Ok, so what of the above is just dead-wrong?