help with fosgate 1100a2 amp

[Perry Babin]

justonemoreamp:
You're right, they should have done something. It would have been easy for them to shut down the supply when a fault occured. I can't understand why they didn't.


ben04srt:
Double-check the emitter resistors. Most meters don't read accurately at low values and you have to be be very careful to make sure you get an accurate reading. For most of my meters, you have to hold the probes on the resistor for a few seconds to let it stabilize. In an amp like this where the transistors will be run hard, it's important that the emitter resistors are very closely matched.

Remember to power up the amp via a 10 amp fuse when you bring it up for the first time. If it blows a 10, you can try a 15 but nothing larger.


impsick:
With the outputs out of the circuit, the gate and emitter resistors are open on one end. The only components that may be able to influence the readings are the protection circuit resistors in parallel with the emitters but their value is generally several hundered times higher than the value of the emitters so they don't have much of an effect.

[ben04srt]

all 10 outputs are off the board
2 bad outputs
with outputs off board emitter resistors read 0.0 ohms , all 10 of them

gate resistors read

1. 100 ohm
2. 100 ohm
3. 100 ohm
4. 100 ohm
5. 100 ohm
6. 112.3 ohm
7. 100 ohm
8. 104.5 ohm
9. 100 ohm
10. 104.7 ohm

[ben04srt]

Perry, Should I replace the high reading gate resistors or just the outputs and see what happens?

Is there anything else I should check and replace while I have it apart?

Thanks
Ben

[Perry Babin]

Of the 3 that are over 100 ohms, only one is technically out of tolerance but I'd change all 3.

If you have the A06s and A56s, you may as well replace them. I don't like changing parts without a good reason but this amp takes quite a bit of time to repair. There's no reason to take a chance on blowing the outputs for $0.40 worth of parts.

Just for fun... Check the ones you pull to see if any failed. Check them carefully to see if any are leaking.

[ben04srt]

Outputs replaced , a06's and a56's replaced.
Gate resistors replaced
I still have - 52 volts on right channel.

Q221, 222 ,223 all have 13 volts on all three legs.

[Perry Babin]

Do any of the outputs read more than 2v DC from pin 1-3?

If so, which ones?

[ben04srt]

well ,all these
Q 127, 128, 129 , 220, 211, 212, 213, 214, 215
that doesn't seem like good news

[Perry Babin]

I'll assume that the 100 series parts were actually 200 series parts 217...

What about 216?

What is the voltage on them? If all of the same part number have the same exact voltage, you only need to post two voltages.

Are any shorted? Sometimes a defective driver component can cause new FETs to fail. Other times, they can be damaged when they're being soldered to the insulators.

[ben04srt]

q216 WAS AT 2.6 volts

the rest of the 9640's were 14 volts

14 volts with the 5 irf640's

I didn't use the mesha board to reinstall them .

[Perry Babin]

I should of been more clear. I needed the voltage from pin 1-3 (black probe on 3).