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Pioneer SX-636 30V on left output

dlucy said:
Yes, the WZ-140 is a 14V Zener with 0.5W dissipation in a DO-35 package. I can't find my saved-aside PDF of an old cross reference guide and all my 1970's semiconductor cross-references are in storage (I'm in-between moves).
Click to expand...
to easy! 512-1N5244BTR
 
On the power supply, to my untrained eyes it looks like:

Q3, the 2SD313 is supposed to regulate the 34.5V it is fed into the 13.5V it passes to the next board. Looking at the datasheet for the 2SD313 and the KSC2073TU, the latter far surpasses the required characteristics in terms of voltages, but lacks the current-handling (3A in the 2SD313 versus only 1A in the KSC2073TU) offered by the replacement device. MTF's comment about "it's OK if you're talking about the one that only feeds the FM circuit with 13V" probably means "the FM circuit won't draw anywhere near 1A, so the KSC2073TU is good enough to be a replacement for the 2SD313 in position Q3 on the power supply board. I can't imagine why a solid state FM tuner circuit would pull anywhere near 1A and the schematic says it only delivers 75mA, so I think you're safe on this one. Backing up (to the right towards the transformer), it looks like that part of the power supply is fused at 0.5A anyway, so I don't think the transistors would see anything above that. But then again, I'm not an EE.

Q1, the 2SD234 looks like it provides 30V for the other boards (not the FM tuner) and one rail of the B2 going to the power amp. Again, the output pins/posts/lines on the schematic from this part of the circuit appear to be small (7.5mA + 8mA + 9.5mA) and share the same 0.5A fuse off the power transformer, so, if I'm reading it right, the KSC2073TU has plenty of voltage (150v/150v/5v) and enough current-handling (1A) to suffice in this position even though the original 2SD234 is a 3A device. The glaring difference, for me, between the 2SD234 and the 2SD313 (as in "why would Pinoeer use two different devices if they're doing the same job") is the 2SD234 can handle 1.5W instead of just 1W. So, that's heat. I'd recommend you be careful in selecting replacement devices so: 1) they can take a heatsink and 2) you make sure they've got good attachment to a good heatsink. The 13V voltage regulating transistor in my SX-580 showed clear signs of being under-heat-sunk for it's purpose and caused the FM function to stop working until it was diagnosed and replaced.
 
Bassblaster said:
ok so on the power supply,
C945 - 512-KSC1845FTA?
Click to expand...

Well, this one doesn't sound like a good replacement, to me. The KSC1845 can definitely handle the voltages (120/120/5 vs the 60/50/5 of the 2SC945), but the 2SC945 is rated for twice the collector current and base current (100mA vs 50mA and 20mA vs 10mA). I don't know enough to prize out of that schematic the operating and peak currents on Q2, but since those ratings on KSC1845 are so darned low I would look for something beefier there.

When I search on Mouser for
  • Discrete semiconductor - stocked - transistor - BJT - through hole
then filter for
  • NPN or NPN,PNP
  • Single (configuration)
  • At least 60V Vcbo
  • At least 50V Vceo
  • At least 0.15A Ic (DC collector current is the Mouser column. I hope I'm translating Ic to DC collector current correctly)
  • At least 250 MHz fT
I get 17 matches and a bunch of KSC945 versions. I'd recommend using the KSC945 to replace Q2 2SD945 on the power supply. And you can get 100 of them for $5. Whoo hoo!

Can anyone agree with that? Or point out how I'm doing the replacement-selection process wrong?
 
petehall347 said:
2SD313 tip31a
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i saw and considered the TIP31A but as Doug said, its fused at 500mA so that beefy TIP is not needed. Now if this was a realistic low end receiver then yes, the TIP31A because realistic used the D313 as outputs in the lower end STA receivers.
 
Bassblaster said:
i saw and considered the TIP31A but as Doug said, its fused at 500mA so that beefy TIP is not needed. Now if this was a realistic low end receiver then yes, the TIP31A because realistic used the D313 as outputs in the lower end STA receivers.
Click to expand...

The pricing on the TIP31A seems pretty low, so that would seem like a good contender. The thing that I still don't fully understand, but which I think is a selection factor, is the fT. The Mouser listing for the TIP31A devices state they are only 3 MHz in terms of fT. I vaguely understand that this value plays a big role when the device plays a role in audio amplification or switching, but I'm really unsure of whether that is a selection factor when the device is used as a voltage or current regulator.

Will someone in the know explain this and help me understand on my own for future lookup work?
 
Ok so let me try to simplify things here.

D313 since its a 500mA 13V rail, 512-KSC2073TU will work.
D234 30V 500mA rail, so 512-KSC2073TU again. D234 isnt heatsinked on the power supply and it just barley gets warm
Whats going to bug me is the new TO-220's have a different pinouts so there goes it looking neat. gonna have to bend leads over eachother.
C945 - 512-KSC945YBU
14V Zener - 512-1N5244BTR

Good?
 
You're right: my verbose rambling doesn't leave a clear trail. Adding to your summary to make it easier on the next person reading the thread for help:

Bassblaster said:
Ok so let me try to simplify things here.

  • Power supply Q3 2SD313 500mA 13V rail - replace with 512-KSC2073TU
  • Power supply Q1 2SD234 30V 500mA rail - replace with 512-KSC2073TU again. No need for heatsink as it just barley gets warm. The replacement KSC2073's package of TO-220will have different pinouts, so be careful matching the leads to the right board holes
  • Power supply Q2 2SC945 - replace with 512-KSC945YBU
  • Power supply D8 WZ-140 14V Zener - replace with 512-1N5244BTR

Good?
Click to expand...

Sounds right to me. Let me know if it works or whether or not I owe you a beer.
 
Bassblaster said:
This is going off track a bit but what class is the amplifier is this? to me it looks like B or AB
Click to expand...
Ight. guess no one know that one.

On to replacing the TO-220's on the power supply board, i think im just going to leave them. the D313 powering the tuner can stay. i never lisiten to the radio anymore anyway so not worth the effort of bending leads to match the different pinout. the TO-92 might come out and the D234 i haven't looked into deeply yet. but it will most likely stay. looks to me at this point ill i have to do is recap the tone board and replace the 1 Zener diode. then i can go on about getting new fuse lamps. 2 of the 7 are burnt out. im thinking Blue LED's
 
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