Hifonics BX1500D

[seankane]

The amp powers up, idles fine. Produces rail and regulated. I also have relay engagement. There is +9.45 volts on negative output terminals. There is no audio. Anyone have any ideas?

 

[Perry Babin]

4080 amp?

Do you have oscillation on all of the output transistors? It will swing from ground to about 70v.

 

[seankane]

It is a 4080 amp.


I no longer have a functioning scope. I have 70vdc on the drains of 4 of the eight output FET's.

 

[Perry Babin]

Don't tell me your 465 died?! mine went down several weeks ago, shorted rectifier.

For the FETs with 70v on the drains, you should see 1/2 of that on the source legs. Is that what you have?

If not, are any of the outputs shorted?

If not, post the DC voltage on all legs of the 4080.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 17:
Pin 18:
Pin 19:
Pin 20:

 

[seankane]

My 465 went down.....lol


I have hardly any voltage on the source legs.


I will post 4080 readings.

 

[seankane]

Pin 1: 11.85
Pin 2: 12.41
Pin 3: 12.42
Pin 4: -0.485
Pin 5: 12.43
Pin 6: 6.04
Pin 7: -0.284
Pin 8: 4.73
Pin 9: 4.73
Pin 10: 11.81
Pin 11: -0.479
Pin 12: -0.480
Pin 13: -0.488
Pin 14: -0.488
Pin 15: 12.46
Pin 16: 12.47
Pin 17: -0.488
Pin 18: -0.488
Pin 19: 9.45
Pin 20: 9.45
I do get a weird reading in circuit between drain and source on two of them. .1 ohm like I'm touvhing my leads together.

 

[Perry Babin]

Pull and check those out of the board.

 

[seankane]

4 out of the 8 outputs read 5 ohms drain to source out of circuit. With all the outputs removed I get +3.457 vdc on all the output terminals.


I should probably order a 4080 as well?


Did the readings look ok on the 4080?

 

[Perry Babin]

I'd suggest replacing the 4080 if any outputs failed.

Do those FETs still read 5 ohms drain to source if you connect a jumper from gate to source?

With no jumper ,what's the resistance from leg 1 to the other legs. It should be infinite.

 

[Bertje]

I had the same amp few weeks ago. Defect IRF3710, replaced them with IRF3710z. Amp was working ok but hours later blew again the IRF3710z's and power supply mosfets.
Then replaced the HIP4080 also, and all mosfets. Checks also the resisistors near the HIP4080.
Now it's working ok for weeks.

There is still a high pitch noise from the subwoofer, can you confirm this is normal on all these BX1500d? The filtercaps in the outputfilter are ok (capacitance and ESR). With some larger capacitance add the noise is less (...off course)

 

[Perry Babin]

If it sounds like the following file, it's likely normal but would vary from amp to amp. It's caused by not having synchronized oscillators between the power supply and the class D section.
http://www.bcae1.com/temp/cooleditmixedoscillator01.wav

If you have any other questions, please start a new thread.

 

[Bertje]

Just like that sound it is, so normal and by design..

 

[Perry Babin]

That is normal for amplifiers without synchronized oscillators. Only a small number of amps that use the 494 type controller have synchronization. As far as I know, the 1500 doesn't have synchronization.

The noise is rarely a problem when the amp is playing through car subwoofers installed in the trunk of a vehicle.

 

[seankane]

So from reading other posts the IRF3710PBF will not work?


I have to order the IRF3710ZPBF?

 

[Perry Babin]

I have had no luck with the non-Z version in the 4080 amps. They cause all sorts of strange problems like the 540N in some of the Rockford amps. Some amps appear OK but are unreliable. Others will never leave the bench because the problems are so bad.

 

[seankane]

How is the DC offset pot set in this amplifier? Is it like setting a bias pot in a Rockford amplifier? The circuit board designation is VR12.


I want to know if you monitor millivolts on the output terminals while setting this? Am I looking for 0mv or a specific voltage?

 

[Perry Babin]

Measure directly across the positive and negative speaker terminals. You're going to try to get it as close to 0.000v as possible but anything within 25mv is fine.

 

[seankane]

So how does the pot work?


Turning the pot clockwise will lower the voltage?


I have just repaired the amp and all is working well and I have pot fully CCW

 

[seankane]

Ok got it set, ended up with 0.003 vdc.


CW lowers the voltage to a certain point then starts increasing it again.


I turned the pot until getting the lowest reading, then a little more and it started to increase again. I backed it off until getting the lowest 0.003vdc.