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


Paid Member
2004-10-07 6:05 am
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.
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.
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.
Any one find a solution to this odd problem? Beside using another amp.

I have a variable power supply and match the exact voltage coming for the wall plug. When plugged into the var. PS, the blue lights come on and pulls about 0.16 amps. I can vary the voltage +-1 volt and no sound.
Exactly, same problem here - did anyone resolve this? Was wondering if the forward-biased diodes fixed the issue. I can't seem to figure it out either - even the battery I have should be able to output 12v @ 4A and it won't turn on the speakers (only the blue LED). I haven't tried measuring with a multimeter yet though, but wanted to know if anyone got the Pyle PFA300 working with an external battery...Thanks


2014-08-11 6:07 pm
Series Diode(s) will solve the problem

My setup appears to have the same issues. Controlled the supply voltage on a lab power supply. My unit is fine until the voltage exceeds 11.8 Volts at which point the protection relay within the amp will not close and permit the speaker load to be applied. Under that voltage everything is fine. In my case the battery pack I am using (12.57V charged) will need a diode drop to get me in the range required by the amp. Those will higher voltages will require you to series up your diodes to get the sufficient drop. The diodes are a better solution as they will drop the same voltage regardless of current draw. Please use a power diode rated well over the current rating (@A). On mine there is a solid wire in place of an inductor (L5) on the power input so its a convenient place to add the diode. My board has cut traces and kludge wires all over it. Very poorly made. My boss would beat me if a made something that looked like this. On the other hand its cheap and if it burned up I would laugh not cry. Good luck.