LSi25 plate amp question

mlistens03

When I’m running my LSi 25s, the plate amp gets really, REALLY hot, even when it is just switched to on, or I am using it at low volumes. Is this normal? No other plate amplifier that I have dealt with gets this hot, at least as far as I can remember. I will give you guys a exact temperature later, but I’d say it’s probably around 100-110* F. The other amp doesn’t work so I can’t compare it to what is happening to this one. It seems like it would be bad for the amplifier to be this hot all the time, but maybe I’m wrong. Also, this is the temperature on the heat sink, not in the amplifier. It usually is still slightly warm when it is set to auto and it has turned itself off, however when I switch it to off, it becomes cold again (obviously, if it’s doing nothing, it’s not getting hot). Anyway, is this normal, and if not, is it something I can fix?

Thanks again for your help,
Micah

tonyb

Doesn't seem all that hot to me, but the speakers are old so I'd imagine sooner rather than later you'll be needing new ones or rebuilding the old, if your that handy.

Make sure the rear of the speaker isn't up against a wall also, give it some room to breath.

[Deleted User]

Hello Micah,
It is possible the amp's bias is set too high causing the higher temperature. This is similar to having a car's engine idling too high. Usually as long as you can place your hand on the input plate without discomfort there's no case for concern. On most amps there's an adjustment potentiometer and a place to measure in setting the bias. Since you have one amp not working you might contact Polk to see what service is available. They are at 1-800-377-7655 assuming you live in the U.S.

mlistens03

I have contacted Polk regarding the broken amp, and I am going to send it to them (or possibly a 3rd party person, but probably Polk,) to get it fixed, I just haven’t gotten around to it yet. As for the other amp, how do I adjust its bias? Is there a switch inside? And how do I measure it?

Thanks again for your help,
Micah

mlistens03

Tony, it’s not up against the wall, The heat sink is about 4-5 inches from the wall, and the speaker is pointing towards me (probably around 75 degree angle, but I have no idea, that is just a rough estimate).

[Deleted User]

"how do I adjust its bias? Is there a switch inside? And how do I measure it?"

Let me contact my friend, at Polk, and see what he knows.

[Deleted User]

They are checking to see.

mlistens03

Ok, thanks!