Pioneer SX-850 Snap, Crackle and Pop
- Thread starter joe4fun
- Start date
OK ... first off - thank you all for the replies - the popping and cracking was only present in PHONO - FM and AUX work well - I hardly ever use the FM and AUX only use this for playing records - last week a pop and crackle and lost my LEFT channel - from reading posts on here I replaced all the transistors on the AWF 011 bd - same situation - No Left Channel - looking at the schematic the -19V is -48V ??? Has anyone ever seen this?? I followed the signal that back to the Power Supply Bd.- please see the attached file ... any help would be greatly appreciated - please note I know just enough to get myself in trouble - 
Attachments
It would help if you detailed the model number (SX-850?), board number(AWH-059) and part number (Q11?Q12?) because there is never a simple answer.
If the above assumptions are correct, you need 512-KSA940TU for q11,q12 and 512-KSC2073TU for Q9,Q10.
Sometimes the factory part used and a replacement will not directly correspond.
When the phono amp tanks, if it's the power supply, it will kill BOTH channels, not one.
Once new caps and transistors are installed, you should really do the FIRST thing and verify that the phono jacks
in the back are actually connected to the phono inputs and the signal is making it through the switches AND
in the case of PHONO 2 also the left and rightr channels are making it through the MIC jack!!
Use the ohmmeter function of the DMM from the center contact of each of the 4 phono plugs, to pins 19 & 20 of the AWF-011 board. It should show 100 ohms on the switched-to input.
Be aware that an unused (NOT switched to) phono input is connected to ground through each jack's 100 ohm resistor series resistor. Check the resistors as well, in case some schmuck blew them up.
phono 1 left R2
phono 1 right R1
phono 2 left R3
phono 2 right R4
BTW Juicer and especially pjf610 - both should have started their own threads....
Once new caps and transistors are installed, you should really do the FIRST thing and verify that the phono jacks
in the back are actually connected to the phono inputs and the signal is making it through the switches AND
in the case of PHONO 2 also the left and rightr channels are making it through the MIC jack!!
Use the ohmmeter function of the DMM from the center contact of each of the 4 phono plugs, to pins 19 & 20 of the AWF-011 board. It should show 100 ohms on the switched-to input.
Be aware that an unused (NOT switched to) phono input is connected to ground through each jack's 100 ohm resistor series resistor. Check the resistors as well, in case some schmuck blew them up.
phono 1 left R2
phono 1 right R1
phono 2 left R3
phono 2 right R4
BTW Juicer and especially pjf610 - both should have started their own threads....
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I have a SX850 with similar popping issues. Need some help identifying which transistors to replace.
In the previous post, AK'r mattsd recommenced on the Power Amp to replace transistors Q1-Q4. I purchased the correct transistors from Mouser (512-KSA992FBU) but when I looked at Q1 and Q2 on the Power Amp, the original transistors don't look anything like the new transistors I bought (which look like Q7). See pictures of the existing transistors from the power amp (which are actually screwed into the metal plate in addition to being soldered to circuit board).
I'm confused and could use some clarification. Do I use the 512-KSA992FBU transistors to replace the flat original ones in my pictures (the Q2 green and Q1 black ones)?
Believe I got off the rails on this one and could use some re-direction.
In the previous post, AK'r mattsd recommenced on the Power Amp to replace transistors Q1-Q4. I purchased the correct transistors from Mouser (512-KSA992FBU) but when I looked at Q1 and Q2 on the Power Amp, the original transistors don't look anything like the new transistors I bought (which look like Q7). See pictures of the existing transistors from the power amp (which are actually screwed into the metal plate in addition to being soldered to circuit board).
I'm confused and could use some clarification. Do I use the 512-KSA992FBU transistors to replace the flat original ones in my pictures (the Q2 green and Q1 black ones)?
Believe I got off the rails on this one and could use some re-direction.
Attachments
Q1-Q4 are 2sa726 (all 4 of them on the AMP BOARD which is mark AWH-059. ). The board you are showing is the POWER SUPPLY BOARD (AWR-101). The transistors you identify as Q1 and Q2 are on the P.S. board (AWR-101). Suggest for future reference you note the board # and the part name/number as shown on the schematic. This WILL alleviate a lot of people scratching off what little hair they have left, kicking the dog in frustration, and a lot of cussing and yelling in Basements.
Service manual for the 850 is HERE. Scroll down to SX-850 SM. Note the KSA992 are pinned differently from the KSA992, so if you aren't sure of how to orient the new ones, ASK FIRST. In the mean time this thread on BJT replacement and testing will come in Handy. A little homework....... https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/
Service manual for the 850 is HERE. Scroll down to SX-850 SM. Note the KSA992 are pinned differently from the KSA992, so if you aren't sure of how to orient the new ones, ASK FIRST. In the mean time this thread on BJT replacement and testing will come in Handy. A little homework....... https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/
Thanks, larryderounin. I had the service manual but was trying to locate board visually instead of taking easy route -- just look at the board marking numbers.
You say KSA992 is pinned differently...so if I were to replace the new transistor pins in the same exact locations as the old transistor pins, it would be installed on the board incorrectly?
You say KSA992 is pinned differently...so if I were to replace the new transistor pins in the same exact locations as the old transistor pins, it would be installed on the board incorrectly?
That's Right. Not 100% sure but the KSA992 is 180* out from the 2SA725 & 726. DON'T Depend on my MEMORY THO! Check, DOUBLECHECK, and do it again.
Get the Data sheet for the KSA992 (it's on Mouser). It's either E-B-C or E-C-B (Left to Right, Flat facing you) The Data Sheet will tell you EXACTLY what the pin out is. Go to this thread to identify the markings on the board that match the pins. Read and STUDY POST #11 Especially. https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/. DO IT SLOW AND GET IT RIGHT! The Tortoise wins the race(has a working unit at the end). Rushing thru it can and will cause more problems and can cause injury's to both YOU and the unit.
Get the Data sheet for the KSA992 (it's on Mouser). It's either E-B-C or E-C-B (Left to Right, Flat facing you) The Data Sheet will tell you EXACTLY what the pin out is. Go to this thread to identify the markings on the board that match the pins. Read and STUDY POST #11 Especially. https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/. DO IT SLOW AND GET IT RIGHT! The Tortoise wins the race(has a working unit at the end). Rushing thru it can and will cause more problems and can cause injury's to both YOU and the unit.
