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Class D Switching Power Amplifiers and Power D/A conversion

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Old 17th August 2006, 09:29 PM   #1
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Join Date: May 2006
Default HELP! I botched up my T-Amp Mod!

Ok, I dont have an engineering background, but I was only trying to put my T-Amp in a nice box and fit some proper plugs on the RCA/Speaker inputs! Maybe I'm just a goof-up, but I must say, modding these amps is NOT as easy as I thought and read it would be! Especially if you're going to remove the mini-phone jack as I did. The instructions seem simple enough, but in practice, the circuitry is very small.... Anyway! Here's a crude map of the problem:

DIAGRAM OF UNDERSIDE OF T-AMP CIRCUIT BOARD:

7-pin volume/pwr connector
1 2 3 4 5 6 7
--------------------------------------
| 0 0 0 0 0 0-0 | c O |
LED| | |
=|== a O | |
| b o | |
--------------------------------------

Legend:

A = Power Input, + {center pin} (I'm presuming)
B = Power Input, - {outer}
C = Left speaker wire (hot)
0 = one of the pins of the power connector

My problem is the first time I tested the modified amp, I somehow managed to get it to blow up my main integrated amp (had to replace the fuse...). I had used a 13v 15w walwart adapter, I don't know if that's what did it. But after that, I was afraid to turn the T-Amp back on, so I went back to try to see what went wrong.

I fixed one glaring problem, whereby oversoldering had cut the trace going from pin 7 on the volume/pwr connector, to (c), which is the left speaker wire (hot). So I soldered a wire on the underside of the board connecting those 2 points. The second problem I found was that pins 6 & 7 were supposed to be connected, according to an unmodified T-Amp that I have, but for some strange reason, they were not making contact. So I added some solder between pins 6 & 7, on the underside of the board.

Figuring things should work out now, I carefully checked the connections and tried the amp with a 12v 1000ma walwart. The LED wouldn't even power on. When I tried it with another walwart, a 12v 500a type, I found the LED flickers on for a nanosecond, then shuts off. So next I checked the pins on that volume/pwr connector.

I found that on my modded amp, when I touched the probe from point (a) to the pins on the connector, only pin 2 failed to register a connection. On the unmodded amp however, pins 2, 3 & 4 are supposed to be "off" (not connected to point A). I have no idea why pins 3 & 4 on my modded amp are making a connection to point A (and point B). Those pins have not been touched and aside from pins 6 & 7, that area of the amp was not worked on.

Q. Could that be the reason my T-Amp is not turning on and if so, how can I get pins 3 & 4 to work properly in conjunction with the power input (points a & b)?[
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Old 18th August 2006, 09:00 AM   #2
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First of all I know nothing of the SI amps, which is what I presume you're talking about.

A quick search however shows some T amps surviving at just over 13V... but YMMV.

I honestly can't make heads or tails of your diagram nor description. It's kind of sounding like you should acquire another amp and start over though.

Might I recommend you look up a few soldering tutorials online, and perhaps practice on some junk components.
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Old 19th August 2006, 06:03 PM   #3
Davet is offline Davet  United States
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Join Date: Mar 2004
Location: Reston, Virginia (surburb of Wash, DC)
Default Can't read your diagram

Rather than trying to use the leads from the mini phone jack, have the RCAs input directly to the VR control. Two of the wires bring the signal to the VR from the PCB; two return the signal to the PCB; and two for the switch.

Just cut the leads of the two leads that bring the signal from the PCB to VR and splice the RCA lead to the VR input. These are the two wires in the ribbon cable immediately next to the two red power wires. This will take care of the positive leads from the RCAs.

Daisy chain the negative (ground) of the RCAs and connect this lead to the middle wire of the ribbon cable at the PCB. Check with an ohm meter to make sure. The connections are detailed in the first message of the following thread:

Sonic Impact 5066 Parts List & Modifications
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