MTX 1000D Problem

[Exbass17]

Hi there im havin a issue with a MTX 1000D Amp when its powered up it sounds like whining it whines at first then the protect led @ led238 on the board comes on and it sounds like a Vacuum high pitched sound im guessing its the transformer whindings but not for sure has anyone had this issue before ive also compared the power output transistor and the power fet readings with my DMM with my working MTX 81000D and there within the same range all of them does anyone have any suggestions or have expirenced this same issue before?

[Perry Babin]

LED238 is the output enable LED. When it is on, the output drive circuit is switched on (normal operation).

Does the noise get into the audio?

Does it produce clean audio?

[Exbass17]

How about led360 then soon as power is applied with the remote wire charged Led360 stays on then a few seconds later led238 will turn on but it seems like when led238 comes on the noise goes from whinning to like a vacuum or air compressor sound i havnt tried to hook up anything to it to test the sound due to this issue i assumed something wasnt right my 81000D will have a whinning noise when it first starts up but then goes away thats how i knew something wasnt right plus i have it hooked up to a really low voltage/amperage power supply to help dianose the amp im affraid to see what would happen if i was to hook it up to my car battery directly i have also for testing due to post ive read about burning up the fets if something is not working properly i do know this amp requires alot of power but do you think it would be safe to test the sound of the amp with my small 12volt 3.0 amp wall power supply?

[Perry Babin]

I don't know if a 3 amp power supply is enough.

If you connect it to a battery, insert a 20 amp fuse in the B+ line and have all transistors tightly clamped to the heatsink to help protect the amp if there is a problem.

[Exbass17]

By using a 20 amp fuse which is small version i have that you use in a car limiting the wire gauge size to 10 gauge wire would that be safe? Im just curious because it says on the back of the amp on the wiring sticker/amp specs it says use 0/1 guage only ive never tried anything less i dont have a wafer fuse that small

[Perry Babin]

A 20 amp fuse is safe for 10g wire.

You're not going to try to get full power out of it with a 20 amp fuse, you're simply trying to see if it's functioning at a basic level.

[Exbass17]

Right thats all i ever try when dianosing my amps with my small power supply ill keep it down and see what kind of sound i get and let you know thanks

[Exbass17]

I used the 20 amp fuse inline with my 10 gauge wire to my test battery and i got minimal sound from the sub but it seemed clean im assuming the minimal sound was from the input side of the amp working correctly if i turned up the gain knob the speaker would move in or out if i moved the input gain knob also while moving the input knob like i discussed with the air/vacuum noise the noise would increase or decrease while playing with the input knob also i noticed a lil bit of feedback sound like a older tv would pickup if the channel couldnt tune in playing through the speaker along the minimal clean sound from my input source.

[Perry Babin]

It sounds like the VCA has failed. It's an inline 8-pin IC near the RCA jacks. Remove it and jump pin1 to pin 8 with a 1k ohm resistor. Does that make a difference?

[Exbass17]

hey Perry so your saying desolder the IC completely from the board and solder the the 1k resistor in place of pins 1 and 8? is there way to tell which pin is 1-8 will it be imprinted on the board?