Rockford 1500-1bd

[Perry Babin]

If you have 6 ohms across the speaker terminals with the inductor out of the circuit, the problem is almost certainly in the area near the speaker terminals.

Do you have a 2 ohm current limiting resistor?

 

[impactair]

no, but I can pick up a headlamp today. is the H6054 pretty common?

 

[Perry Babin]

I'd recommend buying four 8 ohm 20 watt resistors from Radio Shack and connecting them in parallel.

The H6054 is extremely common. It works but I prefer the resistors.

If the cost isn't significant to you, buy both and use what you prefer.

 

[impactair]

Anything from RS I get 50% off, my wife manages one, that is better. Should I get one of there little pre-drilled pcb's or just solder jumpers between them?

 

[Perry Babin]

You can do it however you want. I'd suggest just twisting the leads of the 4 resistors together.

 

[impactair]

Ok, I picked up the resistors today, so am I putting the inductor back in or should I power it up without?

 

[Perry Babin]

Inductor out and NO connections to the amp but the following:

Connect the B+ from your power supply to one end of the resistors. Connect the other end of the resistors to the positive speaker terminal (yes, speaker terminal). Connect the ground from your power supply to the negative speaker terminal.

What gets hot on the board?

 

[impactair]

Should I put it back in the heatsink, and should I install the new capacitors?

 

[Perry Babin]

No and no.

The problem should be right near the speaker terminals but you should observant to make sure that nothing away from that area is getting hot.

 

[impactair]

Got it.

 

[impactair]

Fever broke today, back to work. I have been sitting for about ten minutes with juice to the terminals and nothing even gets warm to the touch?

 

[Perry Babin]

Disconnect the resistor and measure the resistance again. Do you still read ~5 ohms across the speaker terminals?

 

[impactair]

Yeah, it still reads the same

 

[Perry Babin]

What's the DC voltage across the 2 ohm resistor when it's connected to the amp?

 

[impactair]

Just plugged it up again, reads 5 volts. The board gets hot where the copper is exposed underneath the capacitors that blew. I think just on one side though.

 

[impactair]

It is on both sides, the bare copper gets very hot very quick. I wonder why it did not do this yesterday?

 

[impactair]

If this is a multilayer board does that mean layers are shorting?

 

[Perry Babin]

Yes. You need to cut away the conductive area. If you leave it and the amp drives a full power signal into that area, the board will begin to burn again. You have to cut the conductive area away all of the way back to clean fiberglass.

 

[impactair]

I'm hacking away but I am about to the point where I will have to remove the entire top copper plate that one side of the capacitors mounted to. Will this cause problems with conductivity. This being a multilayer board, do you think it will be difficult to to make connections to anything that is connected to this plate? also this plate is pretty wide, by removing large sections of it can't it cause current handling issues for the remaining pieces of the conductor?

 

[Perry Babin]

The amp may not be repairable. To make it repairable, you MUST get rid of any fiberglass that could conduct between adjacent copper traces. If this is a 2-layer board (only top and bottom), it should be repairable. If it's a 3 or 4 layer board, it may not be repairable until Rockford releases the schematic diagram. Even then, it may not be practical to repair.

If you find copper traces embedded in the fiberglass (not top of bottom traces), this board has more than 2 copper layers and you will likely have to wait until the schematic diagram is released to repair it.

The attached image shows a board with an internal copper layer.