Audiobahn a275hct

[Perry Babin]

8 volts isn't sufficient for the amplifier to function properly.

 

[2fast4u88]

Ok I will go hook it up in the car real quick.

 

[2fast4u88]

IC#
Pin 1: .09v
Pin 2: 2.13v
Pin 3: .03v
Pin 4: .11v
Pin 5: .78v
Pin 6: 1.70v
Pin 7: .00v
Pin 8: .26v
Pin 9: .04v
Pin 10: .04v
Pin 11: .28v
Pin 12: 5.30v
Pin 13: 2.55v
Pin 14: 2.55v
Pin 15: 2.36
Pin 16: .42v

Hooked to the car.

 

[Perry Babin]

Measure the DC voltage across the amplifier's B+ and ground terminals in the vehicle with the amp on.

 

[2fast4u88]

hmmm I see why you asked. As the fluke battery was dead so I was using a a junk sears meter. That I guess is wrong as it is saying 7 volts at the amp wires and battery.

 

[Perry Babin]

If the meter proves to be correct, check all connections on the B+ and ground wires as well as the inline fuse.

 

[2fast4u88]

Put a battery in the fluke and it reads 12volts I had the car running and tested at the battery so I knew it was wrong. Here see if this looks better.

IC#
Pin 1: .211
Pin 2: 4.71
Pin 3: .051
Pin 4: .208
Pin 5: 1.665
Pin 6: 3.538
Pin 7: 0
Pin 8: .596
Pin 9: .078
Pin 10: .078
Pin 11: .602
Pin 12: 10.07
Pin 13: 5.05
Pin 14: .026
Pin 15: .023
Pin 16: .847

Car voltage/battery 12.58 at the amp

 

[Perry Babin]

8 and 11 need to have ~12v. What's the next component on the circuit traces as they lead away from pins 8 and 11 of the IC?

It's possible that the circuit trace should go directly back to B+ so you may have an open trace, an open feedthrough or a bad connection on a jumper wire.

 

[ppia600]

You should also spray all the dust off the board as it can hold moisture when there is condensation from driving with a/c on for a while and then opening doors. Use something safe for circuit boards that dries quickly. Those were pretty beefy amps, we sold them and amazingly had very few problems with the hc models.

 

[2fast4u88]

No ac in any of the cars but i will use compressed air or something. I will look at the amp here in a sec and see what happens.

 

[2fast4u88]

Ok those pins go threw a bunch of resistors among others strung everywhere to the 12 volt input.

 

[Perry Babin]

Does the trace connected to pins 8 and 11 stop and connect to other traces through a diode or resistor?

Or does the trace appear to go directly to the B+ terminal?

 

[2fast4u88]

What I said resistors to diodes to a crap load of the stuff. It looks like it gets its voltage from the bare coil wrapped things honestly. I ohm tested it with no power to it and from the b+ to those pins is like 1.6M. I snapped some pics of it if that would help.

 

[Perry Babin]

Photos would be helpful (top and bottom of the board in that area).

 

[2fast4u88]

Ok in these pics of the bottom I flipped the amp end over end to keep the top of the chip in the same spot. So when looking at the top view the inputs for the battery are on the right.

The bottom view pics the power inputs would be on the left.

 

[Perry Babin]

Follow the trace endpoint to the other side of the board. See if you can find a bad connection on that trace (jumpers, resistors, diodes...).

 

[2fast4u88]

Ok right there on the top side is where all the corosion is all the way down to where it traces to.

 

[Perry Babin]

Do you have voltage on the trace on the top of the board that connects to that point. These are vias/feedthroughs and they connect the traces on opposite sides of the board. If it's open, it would prevent the voltage from getting through the board.

 

[2fast4u88]

If you look at that cap with out the sticker it is the coroded dot right next to it.

 

[2fast4u88]

Do you have voltage on the trace on the top of the board that connects to that point. These are vias/feedthroughs and they connect the traces on opposite sides of the board. If it's open, it would prevent the voltage from getting through the board.

Not sure I will have to put it back together to check it. But it doesn't look to me to go to the 12volt input at all.