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Project: Pioneer SX-850

Super Noob said:
AMP Assembly (AWH-059)
This amp had a VR bypassed with a resistor, and one channel had replaced outputs. My last SX-850 had two (2) outputs transistors replaced and awhile back I updated it with new outputs, so I was able to replace non-OEM outputs with original devices.

Capacitors:
C1 / 2.2 uF 25v Electro (CSSA) / 2.2 uF 450v EECW-FD2W684KB
C2 / 2.2 uF 25v Electro (CSSA) / 2.2 uF 450v EECW-FD2W684KB
C3 / 1 uF 25v Electro (CSSA) / 1 uF 63v MKS2C041001F00JA00
C4 / 1 uF 25v Electro (CSSA) / 1 uF 63v MKS2C041001F00JA00
C5 / 33 uF 16v Electro (CEA) / 33 uF 25v UKA1E330MDD
C6 /33 uF 16v Electro (CEA) / 33 uF 25v UKA1E330MDD
C11 / 330 uF 10v Electro (CEA) / 330 uF 16v UPW1C331MPD
C12 / 330 uF 10v Electro (CEA) / 330 uF 16v UPW1C331MPD
Click to expand...

The part numbers for C1 & C2 have an extra "E" and the part numbers don't match the description.
This part number (ECW-FD2W684KB) is a 0.68 uF 450V capacitor.
 
Question about diodes on the protection assembly board. It appears you replaced all 1S2472s with 1N4148s, one 1S2473 with 1N4148 and the other with 1N4004. Is there a reason for this? Based on what I gleaned from datasheets, the 1N4148 should be suitable for all.
 
D8 on the protection board is connected to pin 12 and through that to 7.5vac secondary winding and through the transformer to the outside world.

Thus it is subject to the garbage that can be found on the power line.
1n4004 is a robust power rectifier, as opposed to the somewhat more fragile glass diodes that are in a far more (electrically) controlled environment.

Basically in my 40+ years I have seen some blown up D8's and failed D8's (or equivalent from other models).
 
Super Noob said:
Don’t change transistors on tuner unless you are ready to do full adjustments for the AM and FM.
Click to expand...
Not even the notorious 2SC1312? It looks like it's only involved in the mute circuit.
Honestly, I'm not even looking forward to changing the caps on that board. :yikes:
 
markthefixer said:
D8 on the protection board is connected to pin 12 and through that to 7.5vac secondary winding and through the transformer to the outside world.

Thus it is subject to the garbage that can be found on the power line.
1n4004 is a robust power rectifier, as opposed to the somewhat more fragile glass diodes that are in a far more (electrically) controlled environment.

Basically in my 40+ years I have seen some blown up D8's and failed D8's (or equivalent from other models).
Click to expand...
Presumably a 1N4007 would be acceptable. I know I have a boatload of them.
 
Super Noob said:
Most don’t go all the way…. It’s my hobby so I can do work like this. Results are amazing. I bet I have 60 hours on this rig…. It is gone. Sold at a price of a non restored unit to my buddy’s fiend - I true act of good will.

I don’t undo wire wraps…. Tuner board requires about 5 wire wraps pins to be desoldered from the board for required access. This is correct way - don’t undo wire wraps.
Click to expand...

Thanks for the heads-up Super Noob, this 850 has come back, the protection has kicked in. Replaced the remaining 3 caps on the power supply, Q1 &Q2 on the protection board, it still wouldn’t fire up until I removed the new diode I fitted across the relay coil!!. and apparently the tuner fades out and sounds muddy after 20 minutes. Time to replace caps on the tuner board. Then I’ll take it to a mate for realignment. They just keep giving .
 
Super Noob said:
LEDs:
ACtC-3fWiLxFTTHzc-4oqz81TJEUfONZyR81SOjWzOutOZgqbnglzn1Cekavg0Fuu9aqTVq4k0HQZpsBgPDeC_j-qDhsb61GDqHHqz9c7v6qzLyTNv-DDaLX0ZNe6da4jJWzr-UARJUH-FJp-rWXvN6QUbpj=w685-h913-no


ACtC-3dty8qKNMfEXbM_FsRYgalmWzSb9l-rJbG7lr-JkSzQpPZctIHK6lCSQHk2FY_EP19jkJ9vg9yH7GQBLpfS7NDh8Ez_P8CwM7rep-YzU_fB6_3T8trQJessfsZq6RJ9_2fWJ90IZ1bba59P-YFKs9wr=w685-h913-no


ACtC-3fjyMSIu1EH2fjp8VQiHgXTDhUTmSwsJaCDriD8OJgiuVUDiDvKA6A3PIAJRNzje7RTBk2orUoHTyJUq-e-7VRag3Q5hcDtwRsxqS-rOa6QEo6zjV0OY4O-c9BcGMHhAeja0n7u_OnRnnQoJhK5SXz0=w685-h913-no


Yes... I prefer bright white in lieu of yellow.
Click to expand...
Hi. Which LEDs did you buy?
Is it bolt-on replacement for bulbs? Or some PCB modification is needed?
 
Just wire them up (dial lights)…. I have an assortment of 3mm and 5mm LEDs that I use for indicators. Thinking I use 380 ohm dropping resistor or thereabouts. Typically scuff these to limit spotlighting.
 
Good evening. Your work is great, very interesting to follow this miracle. Only two things I would like to ask you, maybe it could be useful to others. You have replaced A733 with KSA992, why not use KSA1015? Seems a better match. You have replaced the 2SC1885 with KSC2383Y, I am wondering if this is a good match (ft 5V, Ic 200mA = 100Mhz for the KSC2383). The C1885 has a ft of 100Mhz but with Ic = 10mA. In the pre drivers stage maybe this can make a difference? Regards
 
Not all (in fact less and less) of these transistor lists are my work. A lot of those then can be hit or miss.

why replace a general logic a733 with ksa992? I buy the ksa992's in the thousands for the price break.
that circuit is 36v, but if the regulator fails, the 1015 will die by over voltage. The ksa992 will live.
The caps might go up like firecrackers, but that's a given... transistor survival worth it.

2sc1885??? not on this board.... awg-038 flat amp, buffer between balance pot and volume control.
and with ksc2383??? NOT BY ME. PERIOD. Offhand I would say that position would be a ksc1845 candidate.

the real fun is the c1775 versus the c1885.... more volts, twice the current and more than twice the watts. the c1775 is generally found between balance and volume, c1885 is an exception.
 
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Always great Mark! Good morning guys. I recently restored a Pioneer SA9800, on NSA boards I found SA733/SC945 and replaced them with the pair KSA1015Y/KSC1815Y. I've read the datasheet and it seems like the best possible replacement. I also found the pair 2SC1885R/ 2SA912R, in that position these transistors act as pre drivers. I also met some strangers, the 2SC1775 and the 2SC1890A. I don't understand what these transistors do. Finally I found the two 2SC1913/2SA913 drivers (with ceramic 47pF cap). Modern transistors aren't that fast, and I don't want to buy fakes. I don't trust builders like ISC, PCM or CDIL, they can fail at any time and I think they don't have the same quality as the originals. I only purchase my components from Mouser or Digikey. I replaced the 2SC945/2SA733 pair with the modern KSC1815Y/KSA1015Y. For the 2SC1775 and 2SC1890A I used the KSC1845F. The drivers pair C1913/A913 has been replaced with original Toshiba 2SC3298Y/2SA1306Y. It was difficult to choose replacements for the C1885R/A912R pre-drivers pair, I'm using the modern KSC2383Y/KSA1013Y, but I'd be happy to know if other options exist as well. I used a 100pF cap to slow down the speed, I could also adjust the idle currend and off set voltages very well. I hope this experience will be useful to many AK members. I'd also like to know what you think about this update, and if there is a pair of pre drivers for that better position than KSC2383Y/KSA1013Y (very high cob on these transistors). Thanks Mark, you are very special! Thanks and greetings guys.
 
my fingers and toes got all tangled up keeping track counting.

then my eyes skidded BACK to the top line. SA-9800 !!!!!!!!!! please start your own thread, this is how hijacks start.

plus the sa-9800 is a NSA amp and kind of finicky on it's transistor types.

slow DOWN the speed??? it WANTS 60 MHz outputs, 100-200 MHz drivers and other fast transistors !

you may have got it running, but I'll bet you don't have a distortion analyzer.

I had a SX-3900 I brought up with 4 MHz drivers. to the expense of 0.05% distortion, NOT 0.005%.
and that doesn't tell the whole tale - it might be generating pulses of ultrasonic energy going straight to your tweeters.
not big, but it doesn't take a lot up there.
 
I want to respect AK's rules, my work on the Pioneer SA9800 is done. I just wanted to give my contribution on this post, where we talk about the replacement of some very old transistors. To be honest, I didn't understand your speech on speed. Thanks
 
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