Old school Coustic Amp 160:turns on with no remote power

[spooney]

I have an oldschool Coustic Amp 160 here that likes to turn on when only power and ground are applied.No remote power necessary.It functions properly other than this issue.No problems with noise or other output related issues.This amp was working fine previously but I had a brain fart one day and reversed the power input polarity.I could smell some warm components but never noticed until recently that it turned on regardless of whether remote signal was applied or not.I'm not looking to spend a ton to repair this as I got the amp for free and I only use it in my basement to run a small setup but I would like to get it back in working order if at all possible.Is there a component that commonly fails when reverse polarity happens that would cause the issue I'm having?

[yesterdaysyouth]

i would start by tracing the path from the remote terminal, probally a small bjt that sends a signal to the pwm to turn the amp on is shorted....

[I Am An Idiot]

As stated above, I seem to remember there being a small transistor on the corner of the board, that when it shorts, it causes the symptoms you are experiencing. I think the remote wire connects directly to the transistor. I looked at ampguts but there is no picture of that amp.

[spooney]

thanks for the replies.I will check out that transistor when I get a chance

[spooney]

i traced the remote wire and found several small transistors connected to the remote lead but none appear to be shorted.i noticed a small ic in the power supply ,does anyone know perhaps if this ic has antyhing to do with turn on ?i really need to post some pics,it would probably greatly simplify this process

[ben04srt]

I had the same problem on mine , but mine was from the coating on the wires breaking inside the grommet and touching pos and remote wire.
You might want to check there to.

[Perry Babin]

What's the part number on the IC?

Yes. Photos would be helpful.

[spooney]

the IC is a njm4558d .I will get some pics asap

[spooney]

here is a link with pics of the top of the board ,I have a pic of the bottom but my putfile account is being screwy right now and will not let me upload anything : http://www.putfile.com/album/171983

[Perry Babin]

Some of these self oscillating amplifiers would start up without remote or fail to shut down if the power supply transistors were leaking (electrically). Pull them and check them carefully on both ohms and diode check to make sure that there is no reverse leakage.