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Old 10-21-2020, 08:29 AM   #1
falcontech
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Default Db Technologies Cromo 12 amplifier no audio

good morning
I have a problem with this amplifier of a DB Technologies chrome 12 powered speaker, I have no output sound, I tried to change (for the moment) only the woofer power amp which is un tda8950th and that little ceramic capacitor highlighted in the photo that was burned when I turn on the amplifier I have the regular signal on the green LED but nothing at the output, the amplifier diagram is not available if someone could help me to repair it I would be grateful PS the components of the case are functional so this problem is excluded

Last edited by falcontech; 10-21-2020 at 08:32 AM..
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Old 10-21-2020, 08:37 AM   #2
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Default 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
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Old 10-22-2020, 03:01 AM   #3
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Default Re: Db Technologies Cromo 12 amplifier no audio

anyone who can help me?
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Old 10-22-2020, 11:33 AM   #4
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Default Re: Db Technologies Cromo 12 amplifier no audio

Did you look up the spec sheet of the TDA8950th?
What pin of the IC the burnt capacitor is connected too?
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Old 10-22-2020, 11:37 AM   #5
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Default Re: Db Technologies Cromo 12 amplifier no audio

Yes pin 14 vddp1
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Old 10-22-2020, 11:42 AM   #6
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Default Re: Db Technologies Cromo 12 amplifier no audio

I replaced the capacitor with a 15nf one, suggested by the guy from the YouTube video but looking at the IC schematic that 15nf is on the boot1 pin so I think I was wrong
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Old 10-22-2020, 12:19 PM   #7
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Default Re: Db Technologies Cromo 12 amplifier no audio

https://www.nxp.com/docs/en/data-sheet/TDA8950.pdf

The schematic on page 22 is for TDA5950J which does not have the same pinout as TDA5950TH, see page 5 for pinout. The 15nf is used on the Boot strap pin.
1) So the cap on pin 14 VDDP1should be around 100nf, same value as used on VDDP2.

2)So you do have Voltage feeding VDDP1?

3) That cap is MLCC (Multi Layer Ceramic Capacitor), the failure mode is shorted circuit, you have to handle it very carefully when installing them, you need to make sure it is not shorted out after installation since they can easily be damaged.
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File Type: pdf TDK_MLCC_common_cracking_modes.pdf (2.00 MB, 5 views)
File Type: pdf FailuremodecauseofMLCC.pdf (179.6 KB, 4 views)
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Old 10-22-2020, 12:27 PM   #8
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Default Re: Db Technologies Cromo 12 amplifier no audio

i have not tried if i have output voltage on pin 14, what voltage should i have at output on pin 14?
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Old 10-22-2020, 12:45 PM   #9
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Default Re: Db Technologies Cromo 12 amplifier no audio

VDDP, VSSP are power supply Voltages.
It will be the same Voltage as on VDDP2.
According to the spec sheet, the typical Voltage for VDDP (+)/VSSP (-) as shown on page 13 is +/-30VDC.
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Old 10-22-2020, 01:00 PM   #10
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Default Re: Db Technologies Cromo 12 amplifier no audio

ok for the assembly of the capacitor I will try to be careful, do you have any advice not to damage it while soldering? as for the output voltage tomorrow i will try, so i have to put the positive lead on the VDDP and the negative lead on the VSSP?
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Old 10-22-2020, 01:03 PM   #11
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Default Re: Db Technologies Cromo 12 amplifier no audio

I forgot, I tested those inductances that are next to the capacitors, which should have 22 uH, only one has 22uH the other three reach 30uH more or less, I suppose they are normal
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Old 10-22-2020, 01:06 PM   #12
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Default Re: Db Technologies Cromo 12 amplifier no audio

Quote:
Originally Posted by falcontech View Post
ok for the assembly of the capacitor I will try to be careful, do you have any advice not to damage it while soldering? as for the output voltage tomorrow i will try, so i have to put the positive lead on the VDDP and the negative lead on the VSSP?
The Voltage testing will be reference to the circuit ground, the unit has dual power supplies (BIPOLAR power supply), one for the positive supply with ref to the circuit ground, and another one is Negative power supply with ref to circuit ground.

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Old 10-22-2020, 01:21 PM   #13
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Default Re: Db Technologies Cromo 12 amplifier no audio

very well I understand, tomorrow I'll let you know, what about inductances what do you tell me?
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Old 10-22-2020, 01:32 PM   #14
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Default Re: Db Technologies Cromo 12 amplifier no audio

Quote:
Originally Posted by falcontech View Post
very well I understand, tomorrow I'll let you know, what about inductances what do you tell me?
https://www.badcaps.net/forum/attach...6&d=1603290566

I only see two large output inductors. What are the printed on top of the inductors?
The value of the inductors are based on impedance of the load.

Last edited by budm; 10-22-2020 at 01:34 PM..
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Old 10-22-2020, 01:49 PM   #15
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Default Re: Db Technologies Cromo 12 amplifier no audio

998amf-134 22uh
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Old 10-22-2020, 02:07 PM   #16
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Default Re: Db Technologies Cromo 12 amplifier no audio

Quote:
Originally Posted by falcontech View Post
998amf-134 22uh
All four inductors have the same prints?
Did you remove them and test them off the board?
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Old 10-22-2020, 02:11 PM   #17
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Default Re: Db Technologies Cromo 12 amplifier no audio

certainly the same abbreviation has been removed from the PCB
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Old 10-22-2020, 02:17 PM   #18
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Default Re: Db Technologies Cromo 12 amplifier no audio

The inductor value will be printed on the inductor itself not on the circuit board since the design may be changed.
220 will be 22uH.
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Old 10-23-2020, 11:03 AM   #19
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Default Re: Db Technologies Cromo 12 amplifier no audio

in the photo the voltages tested I await your news thanks
the points highlighted refer to VDDP (+) VSSP (-)
Attached Images
File Type: jpg 122611684_358485598598415_7590971529546899877_n.jpg (275.3 KB, 13 views)

Last edited by falcontech; 10-23-2020 at 11:05 AM..
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Old 10-23-2020, 03:05 PM   #20
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Default Re: Db Technologies Cromo 12 amplifier no audio

Quote:
Originally Posted by falcontech View Post
in the photo the voltages tested I await your news thanks
the points highlighted refer to VDDP (+) VSSP (-)
So both amplifiers have VDDP/VSSP Voltages to run.
How many speakers does this system have since it has two amplifier IC's?
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