power acoustik TS-620-2

[scampo77]

I have this amp here and it is powering up and the LED is coming on green.

there is no sound coming out of it. i even tried playing with the gains and controls and i cant even get scratching.

also there is a light that is certainly part of the appeal of this amp. i dont have any voltage at the bulb is it AC or DC?

[I Am An Idiot]

I thought I knew which amp you had, but you said that the light thing was appealing. If it is an amp with the Plasma Sphere on the top, It needs audio to make the light work. There are also problems with the power supply board of the Light. There are a couple parts that suffer from bad solder joints. But you really need to get the amp producing sound before you assume the light is not working.

[Perry Babin]

Does it have rail voltage on the outputs?

Does it have regulated ±15v on the op-amps?

The plasma display has a weak power supply and they often fail. Generally, the power transistor(s) inside the metal enclosure fail. Be careful when working with it, it produces at least several hundred volts. There will be no display unless there is audio output.

[jol50]

I had one of those, the light is cool but I don't ride in the trunk of my car Anyway, IIRC it had blown outputs and not recalling what LED it showed. Make sure someone has not broken off the RCA and in some the gain control.

[scampo77]

all the legs of all the op amps are reading zero (i measured 4 op amps).

i beleive i found the outputs but the markings are strange,

F25
F0P
50N06

all i can tell is that they are made by fairchild they have that "F" on them, and there is 6 of them. all of them have +15v DC on the center legs.

i had the ground lead on the NEG power terminals on the amp.

how do i find out the rail voltage?

[Perry Babin]

Could it be FQP50N06?

Did you have 0v DC on the first leg of the power supply FETs?

To measure the rail voltage, place the black probe on one of the non-bridging speaker terminals and the red probe on the center leg of the output transistors.

[I Am An Idiot]

The output transistors are the larger devices. They are on the end of the amp away from the Power input terminals.

[scampo77]

yes it is a Q in FQP50N06

if the out puts are in fact the 6x FQP50N06. then i am getting 15v DC on all 3 legs. i get the same measurments weather the black lead is on the speaker output or the ground terminal.

also i noticed that a IC marked TL494CN is geting really hot.

i also have 4x TIP36C 0 , 1x mur1620cta and 1x uf16202ct

[Perry Babin]

The FQP50N06s are the power supply FETs. The outputs are likely TIP35Cs and TIP36Cs.

If you have 15v on all 3 terminals of each of the power supply FETs, you have several problems. With the black probe on the chassis ground terminal, you should have 0-5v on pin1, B+ voltage on pin 2 and 0v on pin 3.

Recheck this.

If you have 15v on leg 3, you have an open ground trace or solder connection in the ground circuit path.

[scampo77]

how do i chase something like that down? is there a place i should be looking at more than others? i pulled the board from the heat sink and the underside lookes like an assmbly line workers first day with a solder gun.

i have about 1000 ohms resistance between the + and the - chasis terminals which seems to support your diagnoses.