SA8500 only works on DBT

[merlynski]

Look closely at the trace connected to the other side of C24, (purple rectangle) and recheck the orientation of the transistor connected there. Use the diode test on the meter to check it in place. Red probe to red arrow, black probe to the black arrows (separately). Are you sure you already changed that transistor?


EDIT: add image+

 

[PTL-Pioneer]

Lead resistance starts at 0.3 and gets to 0 ohm fairly quickly. I bridged the bump, no change is resistance still reads 0.3 ohm

 

[PTL-Pioneer]

Yes i replaced it not once but twice, its a KSC1845F, Orientation ECB is correct and mirrors the other side of the board (also KSC1845F) i am 100% certain it is in the correct orientation

 

[merlynski]

Looking back through the posts, I see in #255 that the amp output has a buzz but C32 does not with C24 pulled. Is that correct?

 

[merlynski]

Let's see if I remember where we are:
C16 is out.
C22 is out.
R28 has one end lifted.
C24 is out.
No buzz at C32 with signal tester probe.
Amp output (speaker) now has buzz on left channel with tone control switch on.
Are these all true at this time?

 

[PTL-Pioneer]

Let's see if I remember where we are:
C16 is out.
C22 is out.
R28 has one end lifted.
C24 is out.
No buzz at C32 with signal tester probe.
Amp output (speaker) now has buzz on left channel with tone control switch on.
Are these all true at this time?

Yes this is true at this time

 

[merlynski]

Is the buzz present on the + side of C42 with signal tester probe?

 

[PTL-Pioneer]

@merlynski

Hi again, sorry I have been busy and only got back to it again. Thank you for all you help, I feel really stupid, but the problem has now been solved.
The problem was the led bulb for the power on indicator. The way I had it installed left the wiring for the bulb close to the underside of the tone control board, and that was introducing the buzz on the left channel.
Sitting right under the capacitors that you identified!
I can't believe I was so stupid I did not find it sooner, and I know how much time you invested in helping me, thank you so much

 

[PTL-Pioneer]

I re-routed the bulb wiring to keep it as far away from tone board as possible, unit is back in action, my buddy is delighted and also says thank you to all.

Was driving me crazy

 

[petehall347]

well done to all concerned
happy you found it .

 

[PTL-Pioneer]

Thanks Pete, and thank you for you help, you always chime in and I really appreciate it, thank you for your time, way back you sorted out an sx680 for me too.
A heartfelt thank you, I know patience can be hard to continously provide, especially with my level of knowledge, it must be frustrating for you to continually have to get me out if a bind. Thanks

 

[merlynski]

@merlynski

Hi again, sorry I have been busy and only got back to it again. Thank you for all you help, I feel really stupid, but the problem has now been solved.
The problem was the led bulb for the power on indicator. The way I had it installed left the wiring for the bulb close to the underside of the tone control board, and that was introducing the buzz on the left channel.
Sitting right under the capacitors that you identified!
I can't believe I was so stupid I did not find it sooner, and I know how much time you invested in helping me, thank you so much

You are most welcome. Quite an experience.
That explains the reason it seemed to keep moving around, it was moving around . I kept thinking 'it sounds like antenna noise pickup, caused by those long traces along the side of the pcb.' Sometimes the remote troubleshooting is hindered by the inability to directly SEE what is there.
Glad you solved it!

 

[PTL-Pioneer]

Next up will be an SX750, just a general recap and known troublemaking transistors to be replaced.
I will start a new thread on it, and hopefully will not need any help, and instead add something to the forum instead of taking.
Thank you everyone