Do you have ±15v on the power supply terminals of the TL074?
Do the emitter resistors have rail voltage on them?
Or do you have rail voltage on the collectors of the output transistors?
Do the emitter resistors have rail voltage on them?
Or do you have rail voltage on the collectors of the output transistors?
TL074acn
Vcc= 16.5
Vcc(-)= -16
I have rail voltage on all the outputs ~27 to 26v.
I have signal going into the tl074 and I have amplified signal on the outputs of the tl074 but still no output signal on speaker wires
Vcc= 16.5
Vcc(-)= -16
I have rail voltage on all the outputs ~27 to 26v.
I have signal going into the tl074 and I have amplified signal on the outputs of the tl074 but still no output signal on speaker wires
I have rail voltage on all the outputs ~27 to 26v.
~ typically means approximately.
Is the rail voltage on the collector of all of the outputs or is it on the emitter resistors?
~ typically means approximately.
Is the rail voltage on the collector of all of the outputs or is it on the emitter resistors?
sorry about the grammar above, I took a measurement with negative lead on the collector and Base measured ~27. Then collector to emitter and got ~27.
I did verify that the outputs on tl074 increased with adjust gain knob.
Also I traced the signal up to the relay and if not mistaken not the relay engages it cuts off the audio feed.
I did verify that the outputs on tl074 increased with adjust gain knob.
Also I traced the signal up to the relay and if not mistaken not the relay engages it cuts off the audio feed.
Let's try this another way. Find the two speaker wires that read 0 ohms between them. Place the black meter probe on one of those wires.
Red probe on the various collectors. Do you have positive and negative rail voltage on the various collectors?
Black probe on the same point, do you have any rail voltage on the emitter resistors?
Red probe on the various collectors. Do you have positive and negative rail voltage on the various collectors?
Black probe on the same point, do you have any rail voltage on the emitter resistors?
Using the method you described above I had the 27.5vdc on the collectors of the tip35c and -27.5 on the tip35c collectors.
I also had no voltage on the emitter resistors.
I also had no voltage on the emitter resistors.
Do you read 0 ohms between 1/2 of the emitter resistors and one of the bridging speaker wires and the other 1/2 of the emitter resistors 0 ohms to the other bridging speaker wire?
If so, the relay is not in series with the speaker output wires.
I've seen them use a relay for muting. Do you have voltage across the two traces between the relay and the transformer?
Is one of the traces connected to the primary ground (0 ohms)?
If so, the relay is not in series with the speaker output wires.
I've seen them use a relay for muting. Do you have voltage across the two traces between the relay and the transformer?
Is one of the traces connected to the primary ground (0 ohms)?
I didn’t read any voltage on the relay coil pins, but it sure acts like it is muted. I’m not sure if it suppose to be energized (relay coil) to mute or not energized to mute. I guess I could place a jumper across the relay to see if I get audio.
I finally figured out what the issue was. I traced back the relay coil wiring and found that one side of the coil is connected to acc or remote wire. I found high resistance from a pass-thru to the remote connection. I removed the powersupply caps and found that one caps started to leak and ate away at the eyelet. Replaced caps, ran a jumper wire on the bottom and now I have audio. This amp, the protection relay powers on and open s the contacts. When the relay is powered off it (NC) sends the audio to ground.
Attachments
If that cap leaked, I'd suggest (at least) pulling all of the same make/series and checking them for leakage.
At least heat the terminals of other capacitors to see if you smell burning electrolyte.
At least heat the terminals of other capacitors to see if you smell burning electrolyte.