alpine pdx 4

DREW028 · 2012-02-19 1:08 am

Will these work for the gate resistors?

ERA-14HD220U Panasonic Electronic Components Thin Film Resistors

Perry Babin · 2012-02-19 6:05 am

I don't think that's causing the fault. That's feedback for voltage regulation.

Are there any solder bridges between any of the pads for the output transistors?

Do you have at least 2 legs desoldered from each of the output transistors?

DREW028 · 2012-02-19 3:42 pm

Yes, the legs are lifted way up and no i dont not see any bridges.

Could the fault have anything to do with the second voltage detect?

DREW028 · 2012-02-20 2:27 am

i am picking up .005v on the multiple points on the board. Including the source leads where the FETs would be.

Perry Babin · 2012-02-21 6:57 am

The voltage regulation simply ensures that the rail voltage is constant. It won't cause a fault like this.

Remove R9702 from the circuit, clamp all remaining FETs to the board and insert a 10-15 amp fuse in the B+ line. Power up the amp. If it's not drawing excessive current, watch to see if any components are overheating. If there don't seem to be any problems, post the DC voltage on all legs of the four output FETs.

DREW028 · 2012-02-21 1:44 pm

You said four output FETs, did you mean eight? Or are you saying to check the four power FETs?

DREW028 · 2012-02-21 7:53 pm

I'm guessing I'm mixing up the terminology. I reinstalled the power FETs ( output transistors are still disconnected at the gate and source) The amp turns on but is pulsing like before.

The source legs of the power FETs are pulsing to .545v.

Q9701

Pin 1: 5.5
Pin 2: .019 to 5.34
Pin 3: 3.10 to 5.03

Should I still remove r9702?

DREW028 · 2012-02-22 2:38 am

After reading your write up about tl549 ( similar to 494gs) I can see how pin 4 is effect the IC from performing correctly. Am I understanding this correctly? Now I am very curious about removing r9702.

Perry Babin · 2012-02-22 6:13 pm

Sorry, I was zoomed in too tightly to see the other 4 output transistors.

I'd still suggest removing the resistor.

DREW028 · 2012-02-22 6:36 pm

I will remove it when i get home.

Is the .5V on the source legs of the power FETs something to be considered about?

Perry Babin · 2012-02-22 9:10 pm

The power supply FET source legs should read 0 ohms to ground. If you read 0 ohms to ground, it's likely OK.

DREW028 · 2012-02-22 10:13 pm

What do i use as reference to ground when checking the rectifiers?? The amp ground terminal or??

DREW028 · 2012-02-23 1:42 am

i removed the resistor and the amp isnt pulsing anymore. My power supply is buzzing like its under a large load. The 10 amp fuse hasnt popped but ive only had the amp powered on maybe 5 seconds.

DREW028 · 2012-02-25 2:44 am

I got the power supply working. It ending up being one of the gate resistors.

DREW028 · 2012-02-26 4:28 am

i cant find the datasheet for icc3-TLM-3 (IC's 3652,3651,3602,3601)

All pins read good except for 1,2,14,15,16

Outputs FET's are still disconnected

Perry Babin · 2012-02-27 12:33 am

I don't know what 1 and 2 are. 14-16 can't have the correct voltage unless the FETs are producing a rail-rail square wave.

How many of the output FETs are shorted?

Pacparts can get the ICs but they're $24 each. They may not be defective.

DREW028 · 2012-02-27 12:40 am

3 are shorted between the source and drain the rest read lower than .310v black probe on drain red on source except 1.

How do I get these off the board?

Perry Babin · 2012-02-27 12:42 am

How do you get what off of the board?

Which 3 FETs (circuit board designations)?

DREW028 · 2012-02-27 1:15 am

Sorry, rookie mistake. I forgot to discharge the gate. The outputs test fine. Sorry again. I guess I can put them back in the circuit.

DREW028 · 2012-02-27 1:37 am

On all TLM-E ic's

Pin 1: 4v
Pin 2: 4v
Pin 14: .08
Pin 15: 4.9
Pin 16: 10.5

alpine pdx 4

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