Amp keeps going into protection mode

[dorke]

Please measure the DC voltage (2V range) on R2 at minimum-volume and just a bit before the point it goes into protection.

At that point,
Also measure the voltages on the diodes D8-D10 ,no flipping.
The (+) red probe on the anode and the (-) black probe on the cathode.
And carefully, with D11 lifted ,measure the voltage on the pads(pcb) of D11.

 

[Rick79]

Please measure the DC voltage (2V range) on R2 at minimum-volume and just a bit before the point it goes into protection.

At that point,
Also measure the voltages on the diodes D8-D10 ,no flipping.
The (+) red probe on the anode and the (-) black probe on the cathode.
And carefully, with D11 lifted ,measure the voltage on the pads(pcb) of D11.

OK.
R2 at minimum volume reads .004V & right before trip it reads .010V

D8, D9 & D10 read .018V to .030V at moderate volume and right before trip they read about 1.50V to 2.20V
D11 on the pads has the same readings as D8, D9 & D10

 

[Rick79]

Please measure the DC voltage (2V range) on R2 at minimum-volume and just a bit before the point it goes into protection.

At that point,
Also measure the voltages on the diodes D8-D10 ,no flipping.
The (+) red probe on the anode and the (-) black probe on the cathode.
And carefully, with D11 lifted ,measure the voltage on the pads(pcb) of D11.

Please measure the DC voltage (2V range) on R2 at minimum-volume and just a bit before the point it goes into protection.

At that point,
Also measure the voltages on the diodes D8-D10 ,no flipping.
The (+) red probe on the anode and the (-) black probe on the cathode.
And carefully, with D11 lifted ,measure the voltage on the pads(pcb) of D11.

OK.
R2 at minimum volume reads .004V & right before trip it reads .010V

D8, D9 & D10 read .018V to .030V at moderate volume and right before trip they read about 1.50V to 2.20V
D11 on the pads has the same readings as D8, D9 & D10

 

[dorke]

Rick ,
looks like my last post is lost...
The last measurements are very confusing.

Please add a DCV measurement on R3.
And an AC- voltage measurement on both R2 and R3.
and the diodes has shown below( for all of them like the one shown,no flipping).

 

[Rick79]

Rick ,
looks like my last post is lost...
The last measurements are very confusing.

Please add a DCV measurement on R3.
And an AC- voltage measurement on both R2 and R3.
and the diodes has shown below( for all of them like the one shown,no flipping).

View attachment 27239

Sorry for the late reply, I'll do the readings tonight and post them as soon as i can.

 

[Rick79]

Rick ,
looks like my last post is lost...
The last measurements are very confusing.

Please add a DCV measurement on R3.
And an AC- voltage measurement on both R2 and R3.
and the diodes has shown below( for all of them like the one shown,no flipping).

View attachment 27239

Oh, but did you want these readings in protection mode?

 

[dorke]

No,just a bit before that.

 

[Rick79]

No,just a bit before that.

OK, The amp is at the point before protection mode, D11 is still cut.

R3 reads .007 DCV

R2 reads .252 ACV
R3 reads .002 ACV

did you want the Diode readings in ACV, DCV or just in Diode mode?

 

[dorke]

Diodes in DCV please.

 

[Rick79]

OK these are the readings in DCV. The voltage readings change depending on the music that is being played.
D8 reads .019 to .043
D9 reads .070 to .110
D10 reads .025 to .070
D11 reads .022 to .033 on the pads because it's still cut.

 

[dorke]

Where the diode voltages taken a bit before the protection activated?

 

[Rick79]

Where the diode voltages taken a bit before the protection activated?

Yes

 

[73's de Edd]

.


Sir Rick 79. . . . . . . . . . . . .

Referring between the bottom schematic and photo which I have now placed down at the very bottom:

On the schematic at left center you are seeing the dedicated T1 small power transformer used for the circuitry
which you have been working with. It is then fused and passes to 4 low power diodes, and would be about the
size of the ones which you have been working with, as 1N4148's. But they changed their minds on the design and upgraded to a 1N4XXXX series of "beefier" ones.
You see them being placed side by side just to the side of the the clip in fuse, if you look at the photo.
Their storage reservoir capacitor is that C210 on the schematic and is the larger grey vinyl wrapped capacitor to the end of the diodes, and apparently seems to be assigned a C4 board designation.

Now the maximum demands on this supply, from this boards components, will be the two relays coils, that cluster of BLUE LED's for your display plus a minimal pull from the other circuitry.

The schema says that cap is 100 ufd at 16 v, but confirm that first , by its labeling.

That capacitor case, suggests of a different manufacturer and is certainly LARGE for a 100 ufd a @ 16 VDC.
If it IS a 100 ufd , shunt one of your 100's across it (WATCH polarity ! )and then test for the cutoff threshold, if all of its related parts are still connected up.

We are curious if this power supply has gone "SOFT" on us.

Particularly, if you are still experiencing any sluggishness in getting the units initial power turn on.

73's de Edd




.

 

[dorke]

OK these are the readings in DCV. The voltage readings change depending on the music that is being played.
D8 reads .019 to .043
D9 reads .070 to .110
D10 reads .025 to .070
D11 reads .022 to .033 on the pads because it's still cut.

These measurements are very confusing to me,they don't agree with #163:
"D8, D9 & D10 read .018V to .030V at moderate volume and right before trip they read about 1.50V to 2.20V".

I would take another route of testing:
.
Please note the point the amp trips into protection on the volume dial.
BTW, where is it on the full circle ?

Mow locate Q2,note the way it is connected and mark it.
Remove Q2 from the board and measure it in diode test mode:
B-C,B-E,C-E and flip the probes(a total of 6 measurements).
What do we get?

Now connect the amp to power ,and crank the volume up a bit beyond the marked trip point(the amp will not trip with Q2 out ),
With D11 still disconnected.
Measure the DC voltages on R2,R3 and the diodes,what do we get?

 

[Rick79]

.


Sir Rick 79. . . . . . . . . . . . .

Referring between the bottom schematic and photo which I have now placed down at the very bottom:

On the schematic at left center you are seeing the dedicated T1 small power transformer used for the circuitry
which you have been working with. It is then fused and passes to 4 low power diodes, and would be about the
size of the ones which you have been working with, as 1N4148's. But they changed their minds on the design and upgraded to a 1N4XXXX series of "beefier" ones.
You see them being placed side by side just to the side of the the clip in fuse, if you look at the photo.
Their storage reservoir capacitor is that C210 on the schematic and is the larger grey vinyl wrapped capacitor to the end of the diodes, and apparently seems to be assigned a C4 board designation.

Now the maximum demands on this supply, from this boards components, will be the two relays coils, that cluster of BLUE LED's for your display plus a minimal pull from the other circuitry.

The schema says that cap is 100 ufd at 16 v, but confirm that first , by its labeling.

That capacitor case, suggests of a different manufacturer and is certainly LARGE for a 100 ufd a @ 16 VDC.
If it IS a 100 ufd , shunt one of your 100's across it (WATCH polarity ! )and then test for the cutoff threshold, if all of its related parts are still connected up.

We are curious if this power supply has gone "SOFT" on us.

Particularly, if you are still experiencing any sluggishness in getting the units initial power turn on.

73's de Edd




.

OK, I looked at it, It's a 1000 uf @ 16v

 

[Rick79]

These measurements are very confusing to me,they don't agree with #163:
"D8, D9 & D10 read .018V to .030V at moderate volume and right before trip they read about 1.50V to 2.20V".

I would take another route of testing:
.
Please note the point the amp trips into protection on the volume dial.
BTW, where is it on the full circle ?

Mow locate Q2,note the way it is connected and mark it.
Remove Q2 from the board and measure it in diode test mode:
B-C,B-E,C-E and flip the probes(a total of 6 measurements).
What do we get?

Now connect the amp to power ,and crank the volume up a bit beyond the marked trip point(the amp will not trip with Q2 out ),
With D11 still disconnected.
Measure the DC voltages on R2,R3 and the diodes,what do we get?

View attachment 27305

OK I took a photo of the volume level where it trips.
I then took out Q2 and did the diode readings
B&C .680 / flipped nothing
B&E nothing / flipped .684
C&E nothing / flipped nothing

Then I connected the board again with Q2 removed & D11 still cut. The amp stayed on just like you said, so I then turned the volume up more past the trip mode marking and took voltage readings. The voltage readings bounce around depending on what's playing on the receiver.
R2 .019 to .031
R3 .022 to .470

D8 stays on .003
D9 .145 to .513
D10 .069 to .360
D11 .011 to .085 on the pads.

 

[dorke]

About the Transistor "diode test".
Put the "Red probe" on the Base and check with the "Black one " (without moving the Red) once to the Collector and Once to the Emitter,what do you get?

About the effect of the music that plays on the reading on R3:
With Q2 and D11 disconnected.
Get the volume to about "Half way of the dial".
If possible play the same music track and measure and note the voltage you get on R3.
Now lower the "treble knob" gradually till minimum,what effect does it have on the R3 voltage reading?
remember ,playing the "same audio track".

Put the treble back as it was,and do the same thing with the "Bass Knob"

 

[Rick79]

About the Transistor "diode test".
Put the "Red probe" on the Base and check with the "Black one " (without moving the Red) once to the Collector and Once to the Emitter,what do you get?

About the effect of the music that plays on the reading on R3:
With Q2 and D11 disconnected.
Get the volume to about "Half way of the dial".
If possible play the same music track and measure and note the voltage you get on R3.
Now lower the "treble knob" gradually till minimum,what effect does it have on the R3 voltage reading?
remember ,playing the "same audio track".

Put the treble back as it was,and do the same thing with the "Bass Knob"

With the red probe on the base, I get 685 on the Emitter and 683 on the collector.

I don't have anything to play a certain constant sound, so I wont get accurate voltage readings, The voltages will just bounce around and change with different songs, some have more bass than others. I do know Bass has more of an effect on the voltage readings then the treble does.

It seems like im so close to finding the problem. With me not having a capacitor tester and how the schematics don't match up, I feel like I'm not gonna get anywhere.

 

[dorke]

I agree with you on both the diodes and the capacitors.
The fact that you have the voltage change with the music/bass/treble suggest the caps aren't filtering well the AC.

The transistor Q2 is fine.

As it is,I think you could operate the amp. with the wire cut as we did before.
Inserting the diodes and transistor.
You will not have protection against DCV on the output(this is a rare case,but harmful to the speakers if it occurs),but it will work fine.

 

[Rick79]

I agree with you on both the diodes and the capacitors.
The fact that you have the voltage change with the music/bass/treble suggest the caps aren't filtering well the AC.

The transistor Q2 is fine.

As it is,I think you could operate the amp. with the wire cut as we did before.
Inserting the diodes and transistor.
You will not have protection against DCV on the output(this is a rare case,but harmful to the speakers if it occurs),but it will work fine.

So if somehow the speaker outputs get grounded by a blown speaker or touching wires, Will the amp still be protected? Will one of those internal fuses blow before causing any damage?