Db Technologies Cromo 12 amplifier no audio

[system100m]

Re: Db Technologies Cromo 12 amplifier no audio

Hi, I also have an issue with my Cromo 12.

When powered up, the red led would constantly blink. It will play and sound fine for 10 minutes, and then suddenly the sound would stop and you'd hear some kind of crackles instead. It has two TDA8950TH on the board, is one for the tweeter and one for the woofer? Should I assume if both act the same, then these chips are fine? any other idea?

[budm]

Re: Db Technologies Cromo 12 amplifier no audio

the man of the video explained to me that he put that resistor to bypass this small integrated in the picture (sorry for the resolution) which is a C04R that usually gets damaged, I don't know whether to try to do the same thing, he says that a 3.3Kohm 1/4 watt resistor, looks like 2 watt to me but maybe the video deceives me

That IC is Triple inverters, so I have no idea which one he bypassed and I also have idea how the inverters are being used in the circuit. He must have known how inverters are being used in that amplifiers.
His video also shown a handful of the amplifier IC's, so did he also replace them.
This is tough unit to troubleshoot.

[petehall347]

Re: Db Technologies Cromo 12 amplifier no audio

if there was a schematic it would be easier to say where the signal path is .

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

the man of the video explained to me that he put that resistor to bypass this small integrated in the picture (sorry for the resolution) which is a C04R that usually gets damaged, I don't know whether to try to do the same thing, he says that a 3.3Kohm 1/4 watt resistor, looks like 2 watt to me but maybe the video deceives me

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

do you think I can enter the audio directly to the IC input and bypass the preamp to understand if the problem is at the beginning or at the end of the tracking?

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

I found this too
https://music-electronics-forum.com/...equests/35910-

[budm]

Re: Db Technologies Cromo 12 amplifier no audio

I do not know why he shows TWO removed IC's and the filter caps for the power supply, and why removed the filter chokes and mount it off board. Nothing show about the Tweeter amplifier either, that added resistor for whet purpose?
He should at least put the details in the description.

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

If it helps this is a video of the same amp that has been repaired
https://www.youtube.com/watch?v=pB_XobWmlp8&t=72s

This

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

i figured i have to follow the audio where it starts and where it stops right? but those amps have an audio signal input? to understand if it gets there. then I wanted to ask you if you have seen that YouTube video that I linked at the beginning of my request, where that guy makes a similar repair and makes a bridge with a resistance and I don't understand why

[budm]

Re: Db Technologies Cromo 12 amplifier no audio

Read this post about audio probe/tracer.
https://www.badcaps.net/forum/showth...ht=audio+probe

[petehall347]

Re: Db Technologies Cromo 12 amplifier no audio

you could make a signal tracer easily . all you need is wire . an audio amplifier or headphones . a small capacitor something like .1uf . a chopstick or similar . electrical tape .

[budm]

Re: Db Technologies Cromo 12 amplifier no audio

I had badly seen the measurement on the tester, the value is 4.9 on all pins 6

According to graph as shown on page 7, pin 6 needs ot be >4.2V to be in operating mode, so at 4.9V the IC should be in operating mode.
You now need to find out if you do have audio feeding the IC or not, but since you do not have the scope or Audio tracer, plus we do not have the schematic to help troubleshooting which is making remote troubleshooting very difficult for me.

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

how do we proceed now?

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

I had badly seen the measurement on the tester, the value is 4.9 on all pins 6

[budm]

Re: Db Technologies Cromo 12 amplifier no audio

OK, that cap is connected the same way as CVP caps on page 22 of the application circuit, each pin of VDDP1/VDDP1,VDDP2/VSSP2 should also have one cap to ground for each pin. So look at the VDDP1 or VDDP1/VDDP1,VDDP2/VSSP2 pin cap that is connected to circuit ground.

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

one side of the capacitor is connected to the vddp pin and the other (the internal ones) to the vssp pin I found this in the previous measurement

[budm]

Re: Db Technologies Cromo 12 amplifier no audio

are you talking about the ceramic condenser that initially burned?

Yes, one of that cap is connected to circuit ground.

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

are you talking about the ceramic condenser that initially burned?

[budm]

Re: Db Technologies Cromo 12 amplifier no audio

I used ground circled in red

I cannot tell from the pictures to know what that is connected to.
Thew blown up cap has one end connected to the circuit ground so yo can try using that leg of the cap as circuit ground.

[falcontech]

Re: Db Technologies Cromo 12 amplifier no audio

tomorrow I will do the test again, I would not like that I have set the tester wrong