Amp keeps going into protection mode

[73's de Edd]

.


Sir Rick79 . . . . . . .

Sure looks to me like your protection circuitry has been "hypersensitized" by the those deficiencies that I had mentioned earlier.

A Test:

Test as you have been doing before, for detecting the protection threshold , but put a tic reference mark at the very top of your volume / loudness knob.
You now have that referencing setting being easily repeatable.
Shut down power and place another 100K resistor across R3.
Power up to test just as before and see how much more audio output you can get this time, while referencing to your old knob Tic marked referencing.
And it possibly would not even go into protection mode . . .or at least having a higher level before its engaging.

An additional effect of my mentioned problems up in the U1-U2 circuitry . . . .would be the stut . .stut . . .stutt . . .stuttering of the system on power turn on attempt.

Thasssssit . . . . .

73's de Edd




.

 

[dorke]

I rechecked R3 in DCV2 with the negative and positive probes and its .004 at minimum volume and goes up as high as .300 before protection mode. Sorry, not 1.30

I rechecked R3 in DCV20 with the Ground probe on the Speaker terminal ground and it reads 0.01 on both sides at minimum volume and reads 0.04 to 0.07 on both sides before protect mode

Please repeat the test of #32 this time with the DMM at AC 2V range.

 

[Rick79]

.


Sir Rick79 . . . . . . .

Sure looks to me like your protection circuitry has been "hypersensitized" by the those deficiencies that I had mentioned earlier.

A Test:

Test as you have been doing before, for detecting the protection threshold , but put a tic reference mark at the very top of your volume / loudness knob.
You now have that referencing setting being easily repeatable.
Shut down power and place another 100K resistor across R3.
Power up to test just as before and see how much more audio output you can get this time, while referencing to your old knob Tic marked referencing.
And it possibly would not even go into protection mode . . .or at least having a higher level before its engaging.

An additional effect of my mentioned problems up in the U1-U2 circuitry . . . .would be the stut . .stut . . .stutt . . .stuttering of the system on power turn on attempt.

Thasssssit . . . . .

73's de Edd




.

I dont have any 100k resistors here at home, im gonna have to go buy some. Should i get something around 200k also?

 

[Rick79]

Please repeat the test of #32 this time with the DMM at AC 2V range.

Do you mean the test on post #31?

 

[dorke]

Do you mean the test on post #31?

Yes #31,
but only on R2 and R3
Rick don't go buying anything yet,
we shall try to test with what you have now.

 

[Rick79]

Yes #31,
but only on R2 and R3
Rick don't go buying anything yet,
we shall try to test with what you have now.

Ok, with the meter on AC 2V

R2 reads .125 at minimum volume and .320 before going into protection mode.

R3 reads .009 at minimum volume and .055 before going into protection mode.

 

[dorke]

Rick,
All these measurement shouldn't trip the protect mode.
A digital scope is what we should use but most likely don't have one.
Do you have a cutter?
Would you be able to reconnect a wire back(solder or other way?) if we disconnect one?

 

[Rick79]

Rick,
All these measurement shouldn't trip the protect mode.
A digital scope is what we should use but most likely don't have one.
Do you have a cutter?
Would you be able to reconnect a wire back(solder or other way?) if we disconnect one?

Yeah no scope lol, but i have a soldering iron, solder, a wire cutter and other tools.

 

[dorke]

O.K .
On the Indicator board identify connector S1,it is a 7 pin one.
You should cut the wire that goes to pin 5(DC sense),cut it at a distance so it will be easy for you to reconnect it later.

I can't see the numbering of the pins on S1.
We can identify them like that:
pin 2 should show zero ohms to the black speaker terminal ,measure resistance with the amp disconnected from power.
Pin 7 should show +12VDC relative to pin 2.(with amp powered at min volume).

After you cut the wire of pin5 (without power).
power-up the amp (without speakers!)and crank up the volume ,
does it go into protect?
check the voltages on R2 and R3 as in #46

 

[Rick79]

View attachment 26933 O.K .
On the Indicator board identify connector S1,it is a 7 pin one.
You should cut the wire that goes to pin 5(DC sense),cut it at a distance so it will be easy for you to reconnect it later.

I can't see the numbering of the pins on S1.
We can identify them like that:
pin 2 should show zero ohms to the black speaker terminal ,measure resistance with the amp disconnected from power.
Pin 7 should show +12VDC relative to pin 2.(with amp powered at min volume).

After you cut the wire of pin5 (without power).
power-up the amp (without speakers!)and crank up the volume ,
does it go into protect?
check the voltages on R2 and R3 as in #46

Ok so when i test for resistance on pin 2, i should use the speaker ground terminal for ground with amp powered off.
And find pin 7 with amp powered on, using the speaker ground terminal as a ground also right?

 

[dorke]

Yes

 

[Rick79]

Yes

Ok, Sorry for the delay. So far this is the Voltage readings i got with the meter set to DC20V.
Lookd like the top pin must be pin 7, so now i just count back and cut the wire for pin 5 right?

 

[dorke]

Yes,
cut it about 2" away from the connector so it will be easy to reconnect later.
Was there a zero ohm between pin-2 and the speaker black terminal?

 

[Rick79]

Yes,
cut it about 2" away from the connector so it will be easy to reconnect later.
Was there a zero ohm between pin-2 and the speaker black terminal?

Pin 1 and 2 reads 48.5 ohms with Amp off, ground probe on ground speaker terminal, meter set to 200 ohms.

 

[dorke]

what does the meter show when you short it's probes in 200ohm?

 

[Rick79]

what does the meter show when you short it's probes in 200ohm?

02.5

 

[dorke]

That means that pin 2 is not well connected to ground as it should be.
Can you please check the connection between S1-2 and the"lower side" of C9 or C13.
what do you get?

 

[Rick79]

That means that pin 2 is not well connected to ground as it should be.
Can you please check the connection between S1-2 and the"lower side" of C9 or C13.
what do you get?

View attachment 26945

Like check for continuity?
What do do you mean when you say lower side?

 

[dorke]

Yes ,check resistance(continuity).
"Lower" as is in the diagram,the side that should be connected to ground.

 

[Rick79]

Yes ,check resistance(continuity).
"Lower" as is in the diagram,the side that should be connected to ground.

Yes, there's continuity between S1-2 and C13 and continuity between S1-2 and C9