Yes most likely.
On 2nd thought we can do another test with a small jig.
Do you have 2 AA or AAA 1.5V batteries?
And Some wires?
Yes
Yes most likely.
On 2nd thought we can do another test with a small jig.
Do you have 2 AA or AAA 1.5V batteries?
And Some wires?
As you said :"I have two 2k resistors, an 8.2k, and a 2.2k resistor"
We shall use them for checking.
First thing is to re-solder the diode D8 Leg.
Leave the S1-pin5 wire cut!
100uF caps out of the PCB as it is now.
Build this little circuit, if you don't have a switch, a wire can be fine.
If you have a 2 battery holder with wires it would be perfect,if not ,solder wires directly on the batteries.
Check that the total voltage from the batteries is about 3V,what do you actually get?
Connect it to the circuit, make sure every thing is well isolated including batteries.
Start with the switch open.
Power up the amp(no speakers required).
It should not go into protect mode.
Measure the voltages on R2 and R3.
Now close the switch ,the amp should go into protect mode.
Measure the voltages on R2 and R3.
View attachment 26989
It will prove that in "DC conditions" the protection circuit works as it should.
This "DC condition" is achieved by the strong filtering effect the suspected caps have.
If they fail ,the AC signal at the output will "reach" the protection circuit and trigger the protect mode.
Please measure the voltage on R2 and R3 in the protection mode.
That is not what I'm expecting ,voltage on R3 is too high.
While in protection mode,
please check the following voltages:
The batteries.
Each of the 2 resistors of our Jig (2.2k and 8.2k).
The voltage on the diodes D8-D11(black on the black line of the diode side-the cathode) .
The voltage on R2 and R3.
and voltage on R8.
Rick,
As it is looks like D11 is shorted(1.54-1.51=0.04V.)
Please confirm the voltage on it directly -both probes on it.
Other measurements don't comply with each other for example the voltage on D8 looks "reversed" ,and there are more like that.
Could you please check the voltage on the diodes
View attachment 27035
Wow,this is confusing,hard to read.
looks like you have replaced anode and cathode.
this is the notation:
View attachment 27038
"D9, Cathode side reads 1.10V
D10, Cathode side reads 1.10V"
D9 and D10 have their anode in common not their cathode .
and likwise:
"D8, Anode side reads 0.53V
D11, Anode side reads 0.53V"
D8 and D11 have their cathode in common not their anode .
Also measurement on R3 and D9 do not confirm each other.
No need to flip probes when checking voltage on a diode,
Put the (+)red probe on the anode and the (-) black probe on the cathode.
So,
Voltge on R3=1.09-0.53=0.56, not 1.10v like in post #110
Please re-check the voltages.
no need for resistance checks.
Do you have any diode on hand?
Wow,this is confusing,hard to read.
looks like you have replaced anode and cathode.
this is the notation:
View attachment 27038
"D9, Cathode side reads 1.10V
D10, Cathode side reads 1.10V"
D9 and D10 have their anode in common not their cathode .
and likwise:
"D8, Anode side reads 0.53V
D11, Anode side reads 0.53V"
D8 and D11 have their cathode in common not their anode .
Also measurement on R3 and D9 do not confirm each other.
No need to flip probes when checking voltage on a diode,
Put the (+)red probe on the anode and the (-) black probe on the cathode.
So,
Voltge on R3=1.09-0.53=0.56, not 1.10v like in post #110
Please re-check the voltages.
no need for resistance checks.
Do you have any diode on hand?
I wrote this:
"So,
Voltge on R3=1.09-0.53=0.56, not 1.10v like in post #110"
It should have said post #107.
The voltage on R3 at #107 is too high ,this is what had to be explained.
Now it is ,it was not the voltage on R3 rather the voltage on one of it's legs.
So we have voltage on R3=0.56V and R2=1.54V which is fine.
The diodes voltages are still confusing ,but let's leave it for now.
Now let us change the jig a bit:
Use just one battery instead of two,to produce about 1.5V .
Switch on 8.2K closed(resistor shorted).
Repeat the "protect mode test".
Does it trip?
What are the voltages on R2 and R3( both probes on the resistor)?
Have you got any diode on hand?
The 1N969 is a 22v zener diode,no good for us.
The reading on R2 of 0.8V suggest that the switch (on the jig ) parallel to the 8.2k resistor is open.
Could you please close it (short the 8.2K resistor) and repeat the test.
O.k
that looks fine.
Now let's do the test with a single battery same conditions(8.2k shorted).
only reverse the jig connection ,between S1-5 and the speaker black.
The amp shouldn't go into protect.
What are the voltages on R2 and R3?
like that:
View attachment 27096