Dead Aiwa AV-D50

[budm]

Re: Dead Aiwa AV-D50

So what DCV do you have between GND and Base of Q106 now?
What DCV do you have between the two legs of current sensing resistor?

[budm]

Re: Dead Aiwa AV-D50

Also what DCV do you have between GND and Base of Q107 now?
Is the unit working now?

[jworthin]

Re: Dead Aiwa AV-D50

GND to Base of Q106 is 4.505VDC
GND to Base of Q107 is 1.556VDC

Unit is not working yet.

[budm]

Re: Dead Aiwa AV-D50

GND to Base of Q106 is 4.505VDC
GND to Base of Q107 is 1.556VDC

Unit is not working yet.

Q106 B-E junction of 4.5VDC! That cannot be, the most it will be around 0.6~0.7V.
Are you sure about the E-B-C pin out of the Japanese transistors?
You need to look up the spec of 2SC3052.
If you do have the correct pin out of that transistor then it is bad since no way you can have more than 0.6~0.7V forward bias for the E-B junction.
Same for other transistors that you tested, make sure you do have the correct pinout.
Also make sure all the board mounting screws are tight, you may have bad GND.

[jworthin]

Re: Dead Aiwa AV-D50

I rechecked the Q106 B-E junction and verified it is 4.5V.
I'm confused, this voltage seems to be supplied from the series parts R113, D101, and R114. Without the Q106 transistor (removed) to bias Q107 there is no reduction of the supply 25v so there is 25V across these three components. The zener(D101) is 10V leaving 15V through R114 + R113 = 690 ohms giving 22ma. This 22ma times R114 (220) yields 4.78V bias for Q106. This seems to be about what I am measuring (within 7%). Why can't the bias be more than 0.6~0.7V? Thanks again for helping and answering my questions.

[jworthin]

Re: Dead Aiwa AV-D50

I did another test replacing Q106 and removing Q105. My thinking was to disable the over current latch mechanism. However the result was nearly no conduction in Q108 and Q109 and so no voltage for the zener D101 network and so 0.0V bias for Q106.

[budm]

Re: Dead Aiwa AV-D50

I rechecked the Q106 B-E junction and verified it is 4.5V.
I'm confused, this voltage seems to be supplied from the series parts R113, D101, and R114. Without the Q106 transistor (removed) to bias Q107 there is no reduction of the supply 25v so there is 25V across these three components. The zener(D101) is 10V leaving 15V through R114 + R113 = 690 ohms giving 22ma. This 22ma times R114 (220) yields 4.78V bias for Q106. This seems to be about what I am measuring (within 7%). Why can't the bias be more than 0.6~0.7V? Thanks again for helping and answering my questions.

That is impossible if you understand what the transistor is, please look up transistor and see how it works, how it is bias, otherwise you will not understand how it works and what the Voltages you will expect from it. Did you look up the pinout of the Transistor?
Are you measuring the Voltage between the middle pin of the Transisto and ground to get that 4.5V reading for the E-B junction?
What is your back ground in electronics?

[budm]

Re: Dead Aiwa AV-D50

I did another test replacing Q106 and removing Q105. My thinking was to disable the over current latch mechanism. However the result was nearly no conduction in Q108 and Q109 and so no voltage for the zener D101 network and so 0.0V bias for Q106.

I do not know why you are trying to disable the over current mechanism when I ask you to provide the Voltage reading across the current sensing resistor, that Voltage will tell you if the load is drawing too much current or not.
If you CANNOT follow instruction then I can no longer waste my time helping you.
Post #21:
"What DCV do you have between the two legs of current sensing resistor?"

[budm]

Re: Dead Aiwa AV-D50

I did another test replacing Q106 and removing Q105. My thinking was to disable the over current latch mechanism. However the result was nearly no conduction in Q108 and Q109 and so no voltage for the zener D101 network and so 0.0V bias for Q106.

If you start pulling part without understand the circuit or even know what the proper Voltage for the junction of the transistor should be then you are taking an big chance of blowing the circuit and causes more damage.
I am able to tell you to remove Q106 to get the Voltage output after looking at the schematic and understand what that Q107 is for, I did not just pull that out from the thin air, and also ask you to check the Vdrops on the current sensing resistor to find out if the load is drawing excessive current or not.

[jworthin]

Re: Dead Aiwa AV-D50

I did look up the transistor pinout in two different references.
If the single pin is center top I measured from the lower right pin to GND.
Self taught beginner.
The legs of the current sensing resistor have 0.005V across them.

[budm]

Re: Dead Aiwa AV-D50

I did look up the transistor pinout in two different references.
If the single pin is center top I measured from the lower right pin to GND.
Self taught beginner.
The legs of the current sensing resistor have 0.005V across them.

Can you show me the spec sheet of that Transistor that look up? I NEED to see it.
See the PDF attached and look REAL close as to what the middle pin of that 2SC3052 is!
https://cdn.badcaps-static.com/pdfs/...a9c1d4f05d.pdf

"The legs of the current sensing resistor have 0.005V across them" No over current problem.