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Class D Switching Power Amplifiers and Power D/A conversion

Advice on fixing Topping TP20 mk2
Advice on fixing Topping TP20 mk2
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Old 23rd November 2013, 11:58 AM   #11
Mooly is offline Mooly  United Kingdom
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Advice on fixing Topping TP20 mk2
On a bridged amp (which I think this is) the speaker is connected between the output of two identical amplifiers. As the output of one goes up, the other goes down so that you end up with twice the voltage available to drive the speaker. So no, the speakers are not ground referenced in any way.
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Old 23rd November 2013, 12:45 PM   #12
von Ah is offline von Ah  United States
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Buy a new TPA3116 2.0 board and swap it in! I think it should fit perfecty...
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Old 23rd November 2013, 04:31 PM   #13
SerowMan is offline SerowMan  United States
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Can somebody explain what all the capacitors in front of the outputs do? Also, is there a way I can check to see if it was the TA2020 chip that got zapped then? If it was that, then I can just stop messing with it, say that I've learned my lesson and buy an Audiosource Amp 100 or something.
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Old 23rd November 2013, 05:28 PM   #14
SerowMan is offline SerowMan  United States
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Also, If I am putting it between output and ground, would it be quieter than the other speaker? Because that's what I've noticed.
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Old 23rd November 2013, 05:39 PM   #15
doctormord is offline doctormord  Germany
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They're all part of the output reconstruction filter. Does the error is somewhat touch/bend sensitive? Maybe its just about bad soldering the IC side. This can be tested by putting some force here and there (slighty).

Another test would be to cool down the whole setup. I'd guess you haven't any cooling spray around? You might try isobutane/propane to freeze the filter section (when power is plugged off) and check afterwards. (In cold state)

Edit: As noted from the datasheet, you may check for the following as well:

Voltage on Pin 6 (OVERLOADB) should measure >3.5V in reference to GND (if not, theres a problem on the input stage/side)

Quote:
The OVERLOADB pin is a 5V logic output. When low, it indicates that the level of the input signal has
overloaded the amplifier resulting in increased distortion at the output. The OVERLOADB signal can be
used to control a distortion indicator light or LED through a simple buffer circuit.
Voltage on Pin 18 (FAULT) should measure <1.0V in reference to GND (if not, theres a problem with the IC [thermal overload])

Quote:
The FAULT pin is a 5V logic output that indicates various fault conditions within the device. These
conditions include: low supply voltage, low charge pump voltage, low 5V regulator voltage, over current at
any output, and junction temperature greater than approximately 155C. The FAULT output is capable of
directly driving an LED through a series 2KΩ resistor. If the FAULT pin is connected directly to the MUTE
input an automatic reset will occur in the event of an over-current condition.
In any case, you'll need to put an amperemeter in the +-line of your supply to see any shorts or fried output-stage(s). With no input signal supplied, the quiescent current of the IC is at ~75mA. Having a fried output-stage often results in massive current-draw - heating up the ICs and the coils in the output filter section.

Last edited by doctormord; 23rd November 2013 at 05:54 PM.
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Old 23rd November 2013, 06:48 PM   #16
Mooly is offline Mooly  United Kingdom
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Advice on fixing Topping TP20 mk2
Quote:
Originally Posted by SerowMan View Post
Also, If I am putting it between output and ground, would it be quieter than the other speaker? Because that's what I've noticed.
Quieter, and with DC present because the output of each amp sits at mid supply voltage... so not good for the speakers.
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Old 23rd November 2013, 06:50 PM   #17
SerowMan is offline SerowMan  United States
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Okay, I'm not so sure its not that capacitor that I replaced. When I touch the speaker wire to one side of the capacitor, it outputs at the same very quiet volume as when I connect it to the back of the amp. I'm also pretty sure this pad has a trace to the that output. When I touch the wire to the other lead of the cap, it outputs at full or near full volume. Can anybody explain this?
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Old 23rd November 2013, 07:04 PM   #18
doctormord is offline doctormord  Germany
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--- Despite my previous post, you may try to resolder the whole filter section...
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Old 23rd November 2013, 09:06 PM   #19
SerowMan is offline SerowMan  United States
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Yep, you guys were right. It wasn't the caps. It appears that the amp will output the same volume with or without the caps. Unfortunately when I was trying to check out the TA2020 with my multimeter I think I accidentally bridged couple of pins that I should not have. It immediately shut off and now it will not play any sound. So I think I may be in need of a new amp.
On that note, anybody have any suggestions on a good amp under about $150?
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Old 25th November 2013, 05:32 PM   #20
von Ah is offline von Ah  United States
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Quote:
Originally Posted by von Ah View Post
Buy a new TPA3116 2.0 board and swap it in! I think it should fit perfecty...
Do it.

Click the image to open in full size.

Last edited by von Ah; 25th November 2013 at 05:38 PM.
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