Hifonics BRZ 2100.1D

[jlind54]

I picked this amp up cheap and planned on doing a repair. However this one has me puzzled a bit.

Condition when I received it:
Power supply FETS and gate resistors were mostly smoked, I believe there were 2 resistors out of the 12 that were not burned. Someone had replaced one of the power supply gets with a diode, caused a bit of damage to the pcb in that area. the audio side had 3 shorted outputs.

So far I've replaced the power supply drivers, gate resistors, lets and other misc. resistors that had failed. Removed all the FETS from the audio side. Powered the amp up and checked that the power supply gate resistors had a nice square signal. Put the new FETS in the power and the amp was drawing over 10 amps on power up with audio side components still removed.

Powering the amp through a car bulb so my supply wouldn't shut down, the drive signal to the power supply FETS stays clean but they get warm pretty quickly and the Main rail caps make almost a boiling sound. I removed the diodes and powered the amp up and the over current condition has gone away. I checked the diodes and they seemed to be OK.

Is it possible the main rail caps are somehow shorted? Has anyone seem anything like this on a hifonics amp?

 

[Perry Babin]

Are the solder connections on the rail caps original?

 

[jlind54]

No, it looks like someone either replaced them or attempted to remove them but didn't have a good enough solder iron to properly flow the solder.

I sucked the solder off the pins and put new fresh solder on.

 

[Perry Babin]

It could be that they were either installed backwards or aren't rated for enough voltage.

 

[jlind54]

If I pull the caps and put the diodes back in circuit how much over should I go for a voltage rating on them? 25 volts over rail?

 

[Perry Babin]

The caps are 3300uF@100v. The two nearest to the PS driver board have their negative terminals nearest the driver board. The outer two caps are reversed, compared to the two center caps.

 

[jlind54]

Well, the two outside caps are backwards. What's the chance they are shot or severely life shortend from being in backwards?

Somebody did a number on this thing... Errr

 

[Perry Babin]

They may re-form if you apply power through a limiter. You'll likely see an initial higher current draw then it will taper off in a few minutes. If they didn't short internally, they may be OK.

 

[jlind54]

Well thankfully they appear OK! Guess I should thank whoever attempted to rebuild the amp using diodes inplace of the FETs, I'm sure that helped kill the supply before anything too bad made it to the caps.

 

[jlind54]

Do the 9640's go on the power supply side and 640's on the rca side? I'd imagine these could have been in wrong too at this rate.

 

[Perry Babin]

Look at the silkscreen layout for the output transistors. The 9640s go in the locations that have a nearly filled outline near the edge of the board. The 640s go in the locations with a more open outline.

 

[jlind54]

Is there a way to make the audio side pulse the outputs without them installed. Probably should have checked the drive signal before I put them in. The 9640's heat up rapidly and I got about 25 volts on the output before I shut it down, never did see any drive pulses on the gate resistors on the 9640 side or the 064 side.

 

[Perry Babin]

In the photos I have ,there are 640s and 9640s on both sides of the amp. Is that what you have?

 

[jlind54]

That is what I have, 9640s are near the power supply side and 640's are near the rca side

 

[Perry Babin]

Do the 9640s on both sides of the board heat up at about the same rate?

 

[jlind54]

Judging by just feeling them when power is applied, I'd say yes. The 640's stay cool to the touch.

 

[Perry Babin]

Do you see rail-rail oscillation on the output transistors at any time?

 

[jlind54]

No, time to look over the driver board. Do they deface some of the chips from the factory or is that the handy work of someone else?

 

[Perry Babin]

It's done by the manufacturer. One is a TL072 and the other is an LM211.

 

[jlind54]

Should I bother replacing Q6, Q9, Q12, Q5, Q20, Q21, Q16 and Q23 while I'm replacing the TL072's and the smaller Q11, Q7, Q19 and Q22 transistors on the 2610 driver board or should they likely be ok?