You can salvage or sacrifice an audio cable or you can buy a 3.5mm plug or jack as required.
You can do whatever works for you.

View attachment 306102

There is no need to connect both LEFT and RIGHT channels. MONO will work just as well.
If your powered speaker has a cable with a male 3.5mm plug, then get a mating 3.5mm jack.
If the speaker has female 3.5mm jack, then get a connecting cable or sacrifice a spare cable.
You can omit the plug and jack if you want to sacrifice an old cable. Just cut off the plug at the end of the cable and solder the wire directly to one leg of the capacitor .

One leg of the capacitor is your test probe. The other leg of the capacitor goes to the left or right input channel of the speaker. The capacitor is in series with the input to block DC. Polarity of the capacitor is not important. The GND is brought out to connect to the GND of your guitar amp.

ah that is wonderful mate . thank you !!!

 

To be honest, the powered speaker very likely has DC blocking capacitors already installed as part of the input circuit. We would not know for sure unless we checked. Adding an external DC blocking capacitor does no harm.

 

You can salvage or sacrifice an audio cable or you can buy a 3.5mm plug or jack as required.
You can do whatever works for you.

View attachment 306102

There is no need to connect both LEFT and RIGHT channels. MONO will work just as well.
If your powered speaker has a cable with a male 3.5mm plug, then get a mating 3.5mm jack.
If the speaker has female 3.5mm jack, then get a connecting cable or sacrifice a spare cable.
You can omit the plug and jack if you want to sacrifice an old cable. Just cut off the plug at the end of the cable and solder the wire directly to one leg of the capacitor .

One leg of the capacitor is your test probe. The other leg of the capacitor goes to the left or right input channel of the speaker. The capacitor is in series with the input to block DC. Polarity of the capacitor is not important. The GND is brought out to connect to the GND of your guitar amp.

so what 's my first port of call with my new probe ? was thinking about those diodes I snipped and resolded .

 

No. The speaker probe will be used to search for music content.
Your first stop is to measure DC supply voltages. For that you will use your DMM. You will take two readings with your DMM.

Test #1
Connect DMM black lead to GND. Connect DMM red lead to Test Point 1.

Test #2
Connect DMM black lead to GND. Connect DMM red lead to Test Point 2.

 

No. The speaker probe will be used to search for music content.
Your first stop is to measure DC supply voltages. For that you will use your DMM. You will take two readings with your DMM.

Test #1
Connect DMM black lead to GND. Connect DMM red lead to Test Point 1.

Test #2
Connect DMM black lead to GND. Connect DMM red lead to Test Point 2.

ok .
1: 14.1
2: 14.9

 

ok .
1: 14.1
2: 14.9

I get it, but please pay attention to the sign being displayed on the meter.

 

I get it, but please pay attention to the sign being displayed on the meter.

ah.. -14.9. sorry Teach.

 

Here is your first signal test point.



Connect the GND from the speaker test probe to the same GND as in post #124.
Connect the capacitor test probe to the point indicated by the RED arrow above.

Connect your guitar to the Torque Acoustic amp. Adjust all volume controls (on guitar, amp, tone, speaker amp, etc.) until you can hear adequate sound coming out of the PC powered speaker.

 

Here is your first signal test point.

View attachment 306163

Connect the GND from the speaker test probe to the same GND as in post #124.
Connect the capacitor test probe to the point indicated by the RED arrow above.

Connect your guitar to the Torque Acoustic amp. Adjust all volume controls (on guitar, amp, tone, speaker amp, etc.) until you can hear adequate sound coming out of the PC powered speaker.

low hiss through powered speaker . same kinda white noise as amp speaker

 

Here is your first signal test point.

View attachment 306163

Connect the GND from the speaker test probe to the same GND as in post #124.
Connect the capacitor test probe to the point indicated by the RED arrow above.

Connect your guitar to the Torque Acoustic amp. Adjust all volume controls (on guitar, amp, tone, speaker amp, etc.) until you can hear adequate sound coming out of the PC powered speaker.

There's a burnt resistor just above the Red arrow!

 

There's a burnt resistor just above the Red arrow!

That is an old photo. We can ask TS to post new photos (sharp closeup) of the lower section of the board covering the uA741CP opamps and front panel pots.

 

Here is your next test point.
GND connection will remain the same in future.
(I hope that you are playing the guitar for all tests and the guitar volume is set to maximum.)

 

Here is your next test point.
GND connection will remain the same in future.
(I hope that you are playing the guitar for all tests and the guitar volume is set to maximum.)

View attachment 306177

nothing out of that one . can I disconnect the amp speaker to hear the powered speaker better . ?

 

nothing out of that one . can I disconnect the amp speaker to hear the powered speaker better . ?

Yes. Disconnect the loudspeaker.

 

Use the DMM and measure the voltage at this test point that we are currently testing.

 

I usually don't do this before all the evidence is in. But I would jump the gun and order some 8-DIP sockets and TL071CP op-amps, maybe five of each.

 

Use the DMM and measure the voltage at this test point that we are currently testing.

0.16

 

Some new pics

 

0.16

and the op amps and sockets have arrived .

 

Remove the first uA741CP as shown in post #132.
Install an 8-pin DIP socket.
Insert TL071CP, paying attention to the chip orientation.
Repeat the signal test as per post #132.