Ghost in the house???

[bowdown]

Hello fellow diyers,I have this strange problem with my amp that i built a couple of months ago....The story goes like this......I live alone and in the morning when im about to go to work i make sure that my amp is off,When i return from work abour 10-12 hrs later the amp is on and quite warm which means its been on for a while...It does not do it everyday though and also does it some nights...I have check each connection and they all seem fine...Is there anyone who might know whats happening?

Im using a bulgin momentary switch with a flip/flop circuit which has its own power supply, which is always on unless you unplug the amp from the mains.Please help....

Regards

Bowdown

 

[Bill Fitzpatrick]

I'll bet line noise is making your flip flop - possibly noise coming from the street service or a spike from your refrigerator? Or, maybe it's coming from the air.

Check the power supply for the switch logic.

I guess there is also a possibility that the amp isn't really off everytime you go to work.

 

[bowdown]

Thanx for the info Bill.I will check out what you have said and post my results.The amp gets turned off everytime i finish using it..The reason i know this is cause i have an illuminated logo that lights up as soon as the flip flop circuit turns on and when the flip flop circuit is off the illuminated logo turns off as well. I could be just sitting watching tv or in the other room and the amp will just turn on, normally when it turns on the lights in the house dim a bit as i am using a 1500VA toroidal and 100,000 uF of capacitance...Really should get my act together and sort out my soft start circuit..I might check that refridgerator theory out though...Its probably the ac that is fluctuating or something...Is there anything i can do to fix the problem if this is the case???


Thanx again

Bowdown

 

[Bill Fitzpatrick]

Is the flip flop cmos? Is the supply regulated, clean? Maybe the supply just needs a good bypass cap. Is the flip flop circuit properly implimented?

 

[Enzo]

If you have a CMOS circuit, it could be static related. Do you get zapped grabbing hte doorknob? Also do you have a cat or dog? (I was working on a logic board many years ago and my cat came over and brushed up against my leg. WHAM, a whole row of RAMs died. I use a strap these days.)

Dilute some fabric softener into a spray bottle and spray the carpet in the general area of the system to reduce static buildup. And the carpet will smell nature fresh too.

Possibly enlarge the filters on the flip flop power supply if it is sensitive to mains variations.

Watch the wires from the switch to the flip flop circuit. Make sure to decouple them from the outside world. Series resistors or ferrite beads on the wires, and caps to ground to drain off any static or induced spikes from the environment. Make sure the switch body is itself grounded to the system.

 

[Eva]

These may seem pretty obvious questions, but :

Are the inputs of the flip-flop and all the pushbuttons propely debounced with capacitors to ground?

Are pull-up resistors of low enough value?

 

[sam9]

I think the advice above likely on the mark.

However, just to reassure you that you are not a unique or wierd case,let me recount that I have had exactly the same problem with a powered subwoofer. An appliance in another part of the house that starts up could trigger the "auto-on" switch. Of course like most plate amps it would power off after 20 minutes of no activity.

 

[Stocker]

If it comes ON when the electricity has gone OFF to the house, you may be having frequent interruptions of your power supply to the HOUSE.

 

[destroyer X]

You may consider the possibility of someone trying contact with you.

Believe it or not... are there some strange things hard to explain.

Have you seen the image made by the smoke....when the Trade Center towers were burning....could you see the image

Of course, imagination!

That's all people said.

accept it or not..... but slowly, talk the names...your family died people.... and see if something happens....nothing happened?

So, it is a defective part.


Happening something.... say that was your imagination....because if you say different...they will put you in a Psichiatric hospital to Mad people....and not beeing mad!

regards,

Carlos

 

[anatech]

Hi Bowdown,
Why not setup a reset circuit to ensure the amp stays off when power is re-applied. I'm sure that you don't want the amp to turn on everytime you unplug it and plug it in. This would eliminate your fault.
Most products using logic switching or uP's use a power up "mute" or reset for this reason.
-Chris

 

[bowdown]

Thanx guys for helping me out.My amp doesnt turn on when you unplug it and then plug it back in,However if you have a double wall plug socket on the mains and the amp is pluged into one of them and then you flick the other on/off switch on the mains a few times then the amp just turns on.I will try and get a circuit diagram of the circuit im using and post it here.

Regards

Bowdown

 

[Bill Fitzpatrick]

That pretty much clinches it. Noise on the line is triggering your flip flop.

 

[anatech]

Your circuit is definetly picking up the spikes off the AC and switching. If it makes you feel any better, I have a commercial light timer that suffers from the same thing. A filter right at the AC cord or socket entry may help here. An MOV across the line will help limit spike amplitudes.
-Chris