OXYGEN AUDIO M2.5K

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MY friend brought this amp over..

If the master/slave switch is in slave mode and the rca jacks plugged into the slave jack the amp will work but it wont let you adjust the gains,crossovers or anything..

If i put the switch in master and plug the rca jacks into the input i get no sound at all out of the amp...


I cleaned the switch but still nothing..


Any ideas where to start ??
 
Heres a couple of pics of the board..

I found the 7915 regulator to be defective it had -23 volts on the 3rd leg replaced it and now i have -15 volts..

ON the D1302 muting transistor heres the voltages i get..


Black probe on leg 1 of the muting transistor

Leg 2:0.00
Leg 3:-15.04

Any ideas what to check??
 

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At the risk of being 'reported' for being a 'great big meanie' I'm going to offer something to help close at least ONE of these threads.

MY friend brought this amp over..

He always does.. Get a friend that brings BEER and WOMEN over all the time, and maybe just 1 amp a month. It can change your life :checked:

If the master/slave switch is in slave mode and the rca jacks plugged into the slave jack the amp will work but it wont let you adjust the gains,crossovers or anything..

uh huh.. You do understand that this is the way the amplifier works, right? The slave input takes output from the master amplifier where you make all your adjustments to the crossovers, etc. it ensures a perfect match to the master for good symmetrical bridging of the two. The slave input is tied in AFTER the pre-amp, crossover, and remote gain section.

If i put the switch in master and plug the rca jacks into the input i get no sound at all out of the amp...

Which reaffirms that your issue is boxed into the pre-amp/crossover/gain section. You already found a regulator producing over voltage. This would have me inject a signal into the RCA inputs, making sure I have voltage at the op-amps in this section and then just following the signal from input to output using the chips data sheets. You're losing it somewhere in there. The rest of the amplifier should not be focused on at this moment.


Any ideas where to start ??

See above. Get a data sheet on your op-amps.. fix.

:santa: was here
 
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Do you have rail-rail oscillation on the outputs?

Do you have audio on the small inductor in the center of the board?

Is the relay engaging?



I have rail to rail oscillation on the outputs..

I have no audio on the inductor in the center of the board all i get there is a square wave..

The relay is engaging..

I did some testing of the op-amps and the op-amp in the pic has the following voltages.. Defective or is this normal??

TL072

Pin 1:14.37
Pin 2:14.37
Pin 3:14.43
Pin 4:15.05
Pin 5:14.78
Pin 6:15.00
Pin 7:14.32
Pin 8:-15.01
 

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@ 43 cents a piece, I know it's a tough call. But ya risk a 50% chance that you'll have to remove and resolder twice to try and save that money. Best to consider the part degraded at the least. Comparing the data sheet to your measurements would have confirmed this, BTW. You're not being urged to help yourself because i'm a mean person. You're being encouraged to help yourself, because it helps yourself. :)

Have you invested in the tutorial? If not, have you considered the free resources about the net to understanding these things better? Have you collected a PDF archive of common data sheets? Those are free. Have you collected the free SMT designator sheets about the internet to aid in SMT part identification? All of these things contribute to a better foundation and less reliance. These are all things that help you, not me. Consider it.
 
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