Rockford FOsgate BD1000

[Perry Babin]

A broken connection on the gate leg/pad could cause something like this. Were all of the pads and traces for the gate legs and the gate resistors in good condition?

 

[seankane]

There are a few pads that look a little rough where conected to the gate trace.

Perhaps when I tightened down the mesha board it pulled one of the pads away from a trace and caused the failure.

I am recieving a large shipment of IRF3205's today, I will replace them and be sure to bleed the solder onto the trace a little on all of the gate traces.

 

[seankane]

Tinned power supply fets, checked for leakage all of them good.

Soldered them to the mesha board and checked for resistance betwwen tabs and mesha all read OL

Checked resistance from gate leg of each power supply fet to the other side of the gate resistor and each read 47 ohms or very close to.

Replaced the SG3526 with a new one.

Powered up amp and NOTHING!!!

I have 13.89 volts on pin 14 and 17 from D14.

I have almost no voltage on pin 13 or 16. I dont understand the IC is brand new. I guess it could be bad.

Is there anything else I can test before removing and replacing the IC again???

 

[Perry Babin]

Where did you get the IC?

Before replacing the IC, post the DC voltage on all of the pins.

 

[seankane]

I got the IC's from a seller on ebay who I use on a regular basis for buying fets from. I always have gotten quality parts with matching date codes and have never had any issues. This is the first time I have ordered IC's from them though.

Pin 1: 4.93
Pin 2: 0.004
Pin 3: 4.21
Pin 4: 4.62
Pin 5: 4.94
Pin 6: 0.001
Pin 7: 0.001
Pin 8: 4.51
Pin 9: 3.664
Pin10: 4.25
Pin11: 0.001
Pin12: 4.19
Pin13: 0.009
Pin14: 13.21
Pin15: 0.001
Pin16: 0.008
Pin17: 13.21
Pin18: 4.93

Low voltages on 13 and 16 have me thinking the IC is defective but it is new. I double checked my solder joints and they look good but.......I dont know whats going on. I just want to be 100% the IC is defective before removing it again. The old one was working fine I just thought a new one would be more reliable.

Thoughts?

 

[Perry Babin]

Try replacing the 0 ohm jumper R34 with a 1k resistor.

 

[seankane]

I replaced R34 with a 1k resistor and the amp powers up fine and idles fine.

What is the purpose of this resistor kinda like a fuse?

I am going to bolt it in the heat sink now and see if it trys to short out again.

 

[Perry Babin]

I've never found the brand of ICs that Rockford used and I've never found an IC that would work without the mod. The problem is between the IC that syncs the two oscillators and the 3526. I didn't investigate any further. I made sure that the sync was good with the 1k resistor and that was good enough for me.

 

[seankane]

Thats interesting and good to know. The reason the old one worked is because I took it off of a parts board and it was an original Rockford part.

I have not had a chance to put the board in the sink yet but I will later tonight and re-post my results.

Thanks for your help so far Perry and Happy New Year.

 

[seankane]

I bolted the board down in the sink. Before powering up the amp I tested for resistance between the tabs of the fets and the heat sink. Alot of them show resistance.

Is this normal when bolted into the sink? I want your opinion before powering up the amp. I didnt get any resistance from the tabs to the bottom of the MESHA board while the board was out of the sink and it powers fine out of the sink.

I dont want to fry another 8 power supply fets.

 

[seankane]

Well so far so good amp powered up in sink and all signals looked good through the scope. The amp is playing on the bench and sounds great but I am running it through a 10 amp fuse for now at a lower volume for awhile to be safe.

The output looks clean through the scope as well. Thanks again Perry as always I appreciate your help and patience.