That would suggest that the fault lies on that area of the circuit and that would be delightful news.

What sound source did you use to plug in into the amp?
How did you jumper across the two nodes? Did you use a jumper wire or a capacitor?

Using the sound source that you used to test in post #13, inject a signal at the node with R30, R33, C34.

I used a capacitor 10 uf...will try the signal inject and see

 

I used a capacitor 10 uf...will try the signal inject and see

The source i used was my phone audio..

 

The source i used was my phone audio..

Tried that no sound....

 

Tried that no sound....

Also the thing that bothers me is the pin 4 (lo) on conn10 goes nowhere cant get continuity with the dmm ..the schematic says it goes to R202...i tried putting a jumper from r202 to pin 4 and it goes quiet... must say Thank you once again for your patience and your knowledge. Cheers.

 

Also the thing that bothers me is the pin 4 (lo) on conn10 goes nowhere cant get continuity with the dmm ..the schematic says it goes to R202...i tried putting a jumper from r202 to pin 4 and it goes quiet... must say Thank you once again for your patience and your knowledge. Cheers.

Mr Chips some good news ...put a jumper once again from pin 4 to r202 and tested and node of r32 ,33 and c34 ...i get audio...yessss gotta try at the main inputs and see ..most probably will do that tommorow...kids in bed so dont wanna make much of a noise...incase i get no audio ...maybe any of those opamps maybe???? Cheers and thank you...will keep you posted..ta.

 

Ok. Let's summarize what we have found so far. Please confirm that these findings are correct (1, 2, 3).

1. HF horn works when you inject signal at R213.
2. LF woofer works when you inject signal at R202.

Latest news:
3. Jumper from node R32/R33/C34 to R202 with signal into amp jack works.

Some additional tests still to come:
4. Test that the preamps U1 and U2 are working.
5. Test that DAC signals from U3 are working.

6. Finally check U4 operation.
7. Make sure there is good connection across CON10 and into power amps.

 

For tomorrow.

Reinstall C34.

Use a jumper at R202 as your test probe.

We are going to use this set up to trace the signals around U4 while supplying sound input via the amp input jack.

(Alternatively, we would have been using a PC powered speaker or an oscilloscope to trace the signal - same objectives.)

 

For tomorrow.

Reinstall C34.

Use a jumper at R202 as your test probe.

We are going to use this set up to trace the signals around U4 while supplying sound input via the amp input jack.

(Alternatively, we would have been using a PC powered speaker or an oscilloscope to trace the signal - same objectives.)

Will do.

 

Ok. Let's summarize what we have found so far. Please confirm that these findings are correct (1, 2, 3).

1. HF horn works when you inject signal at R213.
2. LF woofer works when you inject signal at R202.

Latest news:
3. Jumper from node R32/R33/C34 to R202 with signal into amp jack works.

Some additional tests still to come:
4. Test that the preamps U1 and U2 are working.
5. Test that DAC signals from U3 are working.

6. Finally check U4 operation.
7. Make sure there is good connection across CON10 and into power amps.

Actually had injected signal at node of c34 r33 and r32 ..and there was audio..tried injecting at the main input kack of thump 15 and theres no sound.cheers.

 

Here is the strategy. We want to apply input sound source into the amp and try to trace how far the signal reaches in the circuitry.

Apply input sound signal to the TH-15A input jack. Start at zero signal volume and gradually increase the signal level.

Using a 10μF capacitor coupled to R202 as a sound signal probe, connect this capacitor to trace the signals at the test points shown 1 to 7.
Try to test systematically in that order.

Edit: I missed out on test point at U2A pin-1 or either side of C11. We will call this TP-A and TP-B. (If there is sound from TP1 then, of course, you can omit testing TP-A and TP-B).

At this stage, we are not interested in sound level, only that the signal is reaching the LF amp. (Of course, if you get a decent level output, so much the better.)

You may have to adjust the amps settings.
You may want to set the Equalizer controls, HIGH, MID, LOW to the mid positions.
Avoid leaving the LEVEL control higher than mid range to avoid blowing the speaker as well as your hearing.

 

Here is the strategy. We want to apply input sound source into the amp and try to trace how far the signal reaches in the circuitry.

Apply input sound signal to the TH-15A input jack. Start at zero signal volume and gradually increase the signal level.

Using a 10μF capacitor coupled to R202 as a sound signal probe, connect this capacitor to trace the signals at the test points shown 1 to 7.
Try to test systematically in that order.

Edit: I missed out on test point at U2A pin-1 or either side of C11. We will call this TP-A and TP-B. (If there is sound from TP1 then, of course, you can omit testing TP-A and TP-B).

At this stage, we are not interested in sound level, only that the signal is reaching the LF amp. (Of course, if you get a decent level output, so much the better.)

You may have to adjust the amps settings.
You may want to set the Equalizer controls, HIGH, MID, LOW to the mid positions.
Avoid leaving the LEVEL control higher than mid range to avoid blowing the speaker as well as your hearing.

View attachment 131715

View attachment 131714

Mr Chips is it ok to leave the sound processor digital board out of circuit cause it sits on top of the preamp...i am gettin an output at pin 5 of u4 but at U2 pin 7 no output...not sure if i need to test U2 pin 7 with the digital board connected??

 

Mr Chips is it ok to leave the sound processor digital board out of circuit cause it sits on top of the preamp...

Yes i get a signal on all test points..with the processor board out of circuit..cheers...could it be the digital board that is the culprit...???

 

Mr Chips is it ok to leave the sound processor digital board out of circuit cause it sits on top of the preamp...i am gettin an output at pin 5 of u4 but at U2 pin 7 no output...not sure if i need to test U2 pin 7 with the digital board connected??

That makes no sense to me. Here is the signal path. (The numbers are not the same as my TP numbers in post #30.)

1. Sound signal is plugged into JR1. This is an XLR jack that supplies a differential signal.
2. U1-A and U1-B amplifies the two arms of the XLR jack.
3. U2-A is a differential amplifier that takes the difference of the two arms. Altogether, U1 and U2-A constitute what is known as an instrumentation amplifier (not to be confused with an instrument amplifier for musical instruments).
4. R9-B is a volume control. (I do not know where this is physically located on the amp.) Edit: this is a two part (ganged) LEVEL control which is mounted on the reverse side of the preamp board.
5. U2-B is a unity-gain buffer. The signal is split two ways and fed to the analog to digital converter (ADC) U3, WM8569.
6. The ADC digitizes the two signals in two separate channels. This is under control of the DSP.
7. The DSP performs digital signal processing such as filtering.
8. The DSP sends the digital information to a two channel digital-to-analog converter (DAC), same U3, split into high frequency (HF) and low frequency (LF) channels.
9. The HF signal is fed to U4-A and the LF signal is fed to U4-B These are identical low-pass filters to attenuate the DAC clock frequency.
10. The HF signal is fed to J3-2 via R24. The LF signal is fed to J3-4 via R31.

This is a continuous chain. Hence you cannot remove the DSP board.
The signal proceeds in sequence 1-10 as described above. Hence you should not be getting a signal if there is no signal in a preceding stage.

Can you post photos of the DSP board and the preamp board?
Edit: I found pictures on the internet.

 

That makes no sense to me. Here is the signal path. (The numbers are not the same as my TP numbers in post #30.)

1. Sound signal is plugged into JR1. This is an XLR jack that supplies a differential signal.
2. U1-A and U1-B amplifies the two arms of the XLR jack.
3. U2-A is a differential amplifier that takes the difference of the two arms. Altogether, U1 and U2-A constitute what is known as an instrumentation amplifier (not to be confused with an instrument amplifier for musical instruments).
4. R9-B is a volume control. I do not know where this is physically located on the amp.
5. U2-B is a unity-gain buffer. The signal is split two ways and fed to the analog to digital converter (ADC) U3, WM8569.
6. The ADC digitizes the two signals in two separate channels. This is under control of the DSP.
7. The DSP performs digital signal processing such as filtering.
8. The DSP sends the digital information to a two channel digital-to-analog converter (DAC), same U3, split into high frequency (HF) and low frequency (LF) channels.
9. The HF signal is fed to U4-A and the LF signal is fed to U4-B These are identical low-pass filters to attenuate the DAC clock signal.
10. The HF signal is fed to J3-2 via R24. The LF signal is fed to J3-4 via R31.

This is a continuous chain. Hence you cannot remove the DSP board.
The signal proceeds in sequence 1-10 as described above. Hence you should not be getting a signal if there is no signal in a preceding stage.

Can you post photos of the DSP board and the preamp board?
Edit: I found pictures on the internet.

That makes no sense to me. Here is the signal path. (The numbers are not the same as my TP numbers in post #30.)

1. Sound signal is plugged into JR1. This is an XLR jack that supplies a differential signal.
2. U1-A and U1-B amplifies the two arms of the XLR jack.
3. U2-A is a differential amplifier that takes the difference of the two arms. Altogether, U1 and U2-A constitute what is known as an instrumentation amplifier (not to be confused with an instrument amplifier for musical instruments).
4. R9-B is a volume control. I do not know where this is physically located on the amp.
5. U2-B is a unity-gain buffer. The signal is split two ways and fed to the analog to digital converter (ADC) U3, WM8569.
6. The ADC digitizes the two signals in two separate channels. This is under control of the DSP.
7. The DSP performs digital signal processing such as filtering.
8. The DSP sends the digital information to a two channel digital-to-analog converter (DAC), same U3, split into high frequency (HF) and low frequency (LF) channels.
9. The HF signal is fed to U4-A and the LF signal is fed to U4-B These are identical low-pass filters to attenuate the DAC clock signal.
10. The HF signal is fed to J3-2 via R24. The LF signal is fed to J3-4 via R31.

This is a continuous chain. Hence you cannot remove the DSP board.
The signal proceeds in sequence 1-10 as described above. Hence you should not be getting a signal if there is no signal in a preceding stage.

Can you post photos of the DSP board and the preamp board?
Edit: I found pictures on the internet.

Yes had the digital board out of circuit and with a jumper and 10uf cap at one end of connector 10 pin 4 and the other end of the jumper tested at all the test points you suggested i got a signal from the input jack of th15....will test again just to make sure...by the way love the way how you explain things in detail detail ...you the man!!

 

Yes had the digital board out of circuit and with a jumper and 10uf cap at one end of connector 10 pin 4 and the other end of the jumper tested at all the test points you suggested i got a signal from the input jack of th15....will test again just to make sure...by the way love the way how you explain things in detail detail ...you the man!!

I think i may have done some incorrectly...will read your post once again and try .dinner time now.

 

Yes had the digital board out of circuit and with a jumper and 10uf cap at one end of connector 10 pin 4 and the other end of the jumper tested at all the test points you suggested i got a signal from the input jack of th15....will test again just to make sure...by the way love the way how you explain things in detail detail ...you the man!!

Ok. I could not find clear, well focused photos of the board.
Can you take high resolution photos of the preamp board and the DSP board?
PM me and I will send you my email address or post them in a drop box somewhere. I don't know the size limits AAC imposes on photos.

 

With the DSP board removed we can do some testing by jumpering across two nodes.

1. Remove C34 and jumper from TP1 to TP3. This tests LF channel while bypassing DSP (or you can connect to R29-R30 node and leave C34 in place).

2. Remove C30 and jumper from TP1 to TP2. This tests HF channel while bypassing DSP (or you can connect to R22-R23 node and leave C30 in place).

Avoid testing at high sound levels.

 

Ok. I could not find clear, well focused photos of the board.
Can you take high resolution photos of the preamp board and the DSP board?
PM me and I will send you my email address or post them in a drop box somewhere. I don't know the size limits AAC imposes on photos.

Will do.

 

Will do.

 

View attachment 131748

Thats the preamp board