Blown HIFONICS BXi-1600D (HIP4080AIPZ inside)

[brandes.cm]

AndreyK wrote"
Hi everyone,
I am new to this forum as like as to Class D. But anyway, need some help.
Several months ago got blown Hifonics bxi1600d for reasonable price and just some weeks ago started to find the problem.

Firstly, after opening it, I found power supply's MOSFETs blown (many of them were just broken in halves, many had blown legs). Of course, there was just continuous current drain through the amp and nothing else. Fuses were good.
Replaced all 12 of mosfets with irf1404 and tried to check it. Nothing happened, but this time the TL494 was just trying to start as soon as the supply voltage was just over 8V. Seemed like there was a short somewhere in the amplifying section.

Got all 12 IRF3710's off the pcb, and found 2 of them shorted: one from Drain to Source and another one from Gate to Source. Replaced them. The amp was still in protection mode (red led). Tried to change the HIP4080AIPZ with new one and nothing happened.

What I have now:
1. Power supply is absolutely Ok. Mosfets are cold at 2Amps without any heatsink.
2. When all the IRF3710s and the HIP are out of the board, the green led is shining just like the AMP is ready. The voltage on big caps never exceeds +/-79.5V, current drain is about 1.7A at 14V and voltage between HIP's 4 and 15-16 pins is slightly over 13V.
3. When all mosfets are at their places, and the HIP is out of the board, the green led shines again.
4. When I put the HIP into the socket, the AMP goes to protection mode. The current is 1.8 to 1.9Amps and almost nothing is hot. The supply voltage of the HIP is again about 13V. The 1st pin have about 12.8V, the 10th has almost 80V - is this normal? At 3th pin there is also about 13V, looks like the AMP disables the HIP all the time.
5. When I put 3th leg of HIP out of the socket, the green LED starts shining, but there is no sound at the output.

What should I inspect else to get closer to solving this problem?
Know here is enough of them who has the experience in this kind of amps, especially based on HIP4080. So very hope on your help.
P.S. And sorry for my English, it's a little hard to describe all the situation just like it is."

[brandes.cm]

Check for shorts, 80V on pin 10 indicates a failed fet or solder short.

Pin 3 is the disable pin, driven to 5V when in a fault condition.

Pull the outputs and place the 4080 in the socket and check for gate drive signals on pins 11,13,18,20. You may have to lift pin 3 again(tie it to gnd) to have the outputs function.

Cory

[AndreyK]

Here are the voltages on HIP socket (with IC out, no mosfets) I have right now:
1) 13.1V, 2) 13.5V, 3) 0V, 4) 0V, 5) 0V, 6) 4.2V, 7) 3.6V, 8) 0V, 9) 0V, 10) 13.1V, 11) 0.2V, 12) 3.4V 13) 0V, 14) 0V, 15) 13.5V, 16) 13.5V, 17) 0V, 18) 0.2V, 19) 3.6V, 20) 0.2V.
Also there is only 3.6V on ZD1 - which nominal should it have?

Idle current from 14V is about 1.7A without the HIP. When I insert it, I have 5W or 10W power rise (I have 2 of them) with no mosfets in the board, voltage on 15,16 pins falls to 6~10V, the power green led shines dimmer. So I suppose the IC is dead.
I think I have to buy another HIP for the first.
What should I inspect else before putting the HIP in?

Unfortunately, I have no abilities to get IRF3710Z`s now, excepting the one buying them for about $5-6/pc (12 in total), when have about 10 of good (original) IRF3710`s for tests. Hope they will work with a new IC.

p.s. thanks, Cory.

[brandes.cm]

Check for shorts where the output fets solder in, something is pulling your supply down when the 4080 is in the circuit. You could leave one leg of the 4080 out of the socket one at a time to see if your supply comes back up. Then you know what leg is causing your problem.

The datasheet is helpful on this chip as well.

http://www.intersil.com/data/fn/fn3178.pdf

[AndreyK]

No, nothing happen when I take the HIP's outputs off the socket. Also there are no shorts at output stage mosfets, 100Ohm resistors with diodes, as usually.

Just ordered a new IC, hope I will get it by this weekend and then will continue repairing. But can I still check anything else before putting the HIP in, in order not to kill it (not so cheap for kidding)? It seems like there are no high voltages at pins, but who knows..
Any advice will always be helpful.

[Perry Babin]

If you didn't use the IRF3710Z (<<< Z is VERY important), that's likely your problem.

[AndreyK]

Yes, I have no IRF3710Z's. But what is the differense between Z and non-Z versions excepting the Rdson? They are like about the same by other parameters from datasheets. What is the importance of using 3710Z's? And why were original 3710's working several years before this happened?

[Perry Babin]

Semiconductor manufacturers are constantly trying to reduce the amount of the semiconductor material needed to meet the specs of a device. When they do this, the specs may remain the same (or very similar) but that doesn't mean that the new device will work as it originally did in all equipment. This appears to have happened with the IRF3710. There have been MANY people (myself included) that tried to use the original part number but they simply don't work. The Z version has worked in all instances where there has been a problem.

I've gone as far as taking older IRF3710s from a working amp to install in one that wouldn't work with the new IRF3710s to confirm that the output was the problem (and not the driver IC or other components).

I can't guarantee that this will solve your problem but if this amp were brought to me for repair and had new IRF3710s in it and had the symptoms you described, I would first replace the outputs.

The specs don't work well for choosing outputs in class D amps. Many times, only one particular FET will work in a given amp (or amps using a similar design).

One more thing... Buy ONLY from a reputable distributor. If you buy counterfeit IRF3710Zs, they're not likely to work and you will be more convinced that there are other problems.

I'm assuming that you've checked and double-checked all of the peripheral components around the 4080.

[AndreyK]

Thanks for explanation. Will try to find IRF3710Z's from our stores.

But are there any other mosfets working as well as those 3710Z's with HIP? Can I replace them with sth like stp40nf10? Or what could you advice from your own experience?

Just checked remaining original IRF3710's and found only 8pcs to be absolutely working. Should I try a new HIP with 4 of them at low power output? is there any difference of using 4, 8 or 12(originally) of them as outputs?

And again, the ZD1's voltage.. it seems to be too low. Can it cause problems with output of even damage my HIP? Should I change it with another one? What is its nominal?

[brandes.cm]

According to most people the irf3710Z is the only part that will work. Get some of those parts and get the amp working and then you can substitute others.

FQP70n10 looks to be a closer match, but it doesn't mean it will work in this amp.