Phoenix Gold Titanium 1200.1

[RockfordFIx]

I have a 1200.1 that has some dc on the outputs cause intermittent distortion on the output

 

[Perry Babin]

How much DC measured directly across the speaker terminals?

Scope image of the distorted signal?

 

[RockfordFIx]

I was playing audio with 12” subwoofer, I replaced the gain pot (50k), it was bad, it ranged from 0.5 up to 3 vdc, sounded like my sub woofer coil was scratching. I think there maybe an intermittent race or solder joint issue. I reached out to onemoreamp for schematic

 

[RockfordFIx]

With no load and scope on the output. Bottom seems to clip. If I set the phase from 0 to 180 the waveform clips on both top and bottom

 

[Perry Babin]

Is the audio clean on the output of the op-amp that drives the input of the power amplifier's differential amplifier?

Are the rail and regulated voltages as expected?

 

[RockfordFIx]

Hey Perry I can find anything on this chip. Do you have any thoughts?

Also this amp consists of:
5 x lm833
5 x lm837
1 x lm339
2 x Q 208. 110s

 

[Perry Babin]

https://www.farnell.com/datasheets/102081.pdf

 

[RockfordFIx]

Perry I found clipped waveforms on both outputs of the lm833 on u5. Right above it found a burnt 10 ohm resister reading 288.

 

[Perry Babin]

Did that clean up the audio?

 

[RockfordFIx]

I installed the new 10 ohm resistor and it immediately smoked.

 

[Perry Babin]

Lift pin 8 of U5 and try again.

 

[RockfordFIx]

I replaced the resistor and the lm833 and it did the same thing, looks like one side of that resistor is tied to pin 11 which is V+

 

[RockfordFIx]

Njr13600d

 

[Perry Babin]

Is C572 shorted?

I've never seen a 13600 fail shorted (failure, of any kind is rare) but anything is possible.

 

[RockfordFIx]

I measured 81ohms across c572 and I am also reading -1.2vdc on pin 8 which I was expecting 12-15vdc

 

[RockfordFIx]

I removed that cap and the lm833 (u5) vcc voltages is back

 

[Perry Babin]

Clean audio?

 

[RockfordFIx]

I have clean unclipped audio, amazing call perry