Troubleshooting: T-amp with SLA battery, no sound output

[Sarco3]

Hello,

I'm trying to build a portable PA system/party system. I have a 100w T-amp and a 12v 18AH SLA battery.

When plugged into the wall with a 12v 2A AC adapter, the amp works great--sound is sent to the speakers. Switching to the battery, the amp still turns on but does not click and no sound is sent to the speakers.

Any ideas? Thanks!

[Pano]

Are you sure of the battery polarity? Is the battery fully charged? Will the cable and connector carry enough current (dirty contacts) ? All simple, I know, but those are the first places to look.

FWIW, you will no way get 100W out of a 12V supply using 8 or 4 ohm speakers. That rating is a fantasy.

[cotdt]

could the amp have gone into overvoltage protection? check the voltage on the battery.

[Ford Prefect]

I am having the exact same problem and have been trouble shooting it for hours to no avail. My situation is that I am making a portable boombox. I have made one before with the same design. The only difference between the older one and this one is the older one has a pyle pfa 200 class T amp, and the one I'm working on now has a pyle pfa 300.

The Problem - The amp is connected to one DC plug and run to a 3 pin DC Jack so when I plug in the wallwart, it disconnects the power from the battery. When I plug in the ac adapter to the jack, it works normally. when I am just using the battery it powers on and lights up but no click, and no sound. The battery is putting out 13V on my multimeter. The same battery will also power my other boombox fine.

At the amp input plug it is also putting out 13V when connected to the battery. I'm not sure if this is normal but when I just checked it was putting out 13.47V and steadily dropping (went from 13.47 to 13.33 in about 15 seconds and was still dropping)

At the amp plug it was putting out a steady 11.5V when plugged into the wall.

Now the strange part (for me anyway). When I use this wiring rig and setup on my old boombox it does the same thing to it (power, but no sound). And when I use my older wiring setup and battery that works fine on the older boombox, on the new one, again it does the same thing, power but no sound.

I'm lost and any help would be appreciated.

[sofaspud]

FP, check your wiring again.
My summary of the situation (Is it correct?):
amp 1 - works on AC, old wiring rig; does not work with new wiring rig
amp 2 - works on AC; does not work with either wiring rig

[Ford Prefect]

Yes that is correct. The only thing is, that even if I just eliminate all the wiring and just hook the battery up to the amp via alligator clips, I still get the same result. LED's light up, but no amp activation. and the voltage coming into the amp seems within its parameters.

[sofaspud]

But using the wall adapter works?

If it does, measure the output of the adapter.
If the voltages are both within spec, the amp shouldn't care what the source is.

[Ford Prefect]

yes that is correct. I have a feeling that maybe I'm dealing with two problems, making it harder for me to troubleshoot

[Ford Prefect]

yeah, both voltages are within the parameters. the battery is slightly higher at 13.5 while the AC is 11.5

[sofaspud]

Put a couple of forward-biased diodes in the battery line to drop the voltage below 12V. I know the PFA300 manual says, "Over-voltage protection circuit shuts down the amplifier if input voltage exceeds 14.4 V DC" but with weird behavior like this trust takes a backseat.

If the battery voltage dropped to near 11.5V still doesn't work, I'm going back to checking your wiring.