HIFONICS ZXi 1008 car amp stuck in protect mode

[tscr2015]

Hi everyone and Happy Thanksgiving,

I am working on my friends Hifonics Zxi 1008 car amp that is currently stuck in protect mode, and I need some help with it.

When the amp is powered up it goes into protect mode. I have done a diode check on all of the output transistors which are A1694's and C4467's and all seem to be ok. If I remove one of the driver transistors the protect mode shuts off and the amp will power up however I am still not getting any output from it. The driver transistors are D2061's and B1369's

Any help and troubleshooting tips you could provide would be very helpful and thank you again.

Tom S.

 

[Perry Babin]

Can you install the drivers in either channel and get the amp to power up? That would tell you which channel was defective.

 

[tscr2015]

Can you install the drivers in either channel and get the amp to power up? That would tell you which channel was defective.

If I take out the one driver on the channel that has all of the output transistors in place the amp will power up but I don't get sound from that channel either.

I have included a wide shot picture of the top of the amp board if anyone is interested. I can also take more if more of them are needed as well.

Thanks
Tom S.

 

[tscr2015]

Ok, I just pulled out the same driver that I took out before and the amp powers up just fine but that driver tests ok out of circuit so where else do I need to check?

 

[tscr2015]

Can I take all of the Power Transistors off of the board and will the amp still run with out them and then hook them up in pairs to find the bad parts of the output circuit?

 

[Perry Babin]

The suggestions I made cannot provide any useful information with the outputs out of the board.

 

[tscr2015]

alright, I will put all of the output back in the board and report back. Thank you for your help thus far

Tom S.

 

[tscr2015]

everything is put back to normal now where do I start?

 

[Perry Babin]

Post #2.

 

[tscr2015]

if i take out the drivers in either channel it is still in protect mode

 

[Perry Babin]

That's different than described in post #1. What has changed?

 

[tscr2015]

I don't know. I wish I had a schematic to look at to figure this out. I am wondering if the cost to fix this would out weigh the cost of a new one?

 

[Perry Babin]

With all of the outputs in the board and all 4 drivers out of the board, does it go into protect?

 

[tscr2015]

I Think there is a pair of drivers for each set of the transistors therefore I believe there is 8 driver transistors plus there is a transistor in between the output transistors sets so you can really start to see the problem that I am having trying to keep this mess straight.

 

[Perry Babin]

Without a much better photo, I can't determine if that's correct or not.

The drivers will have their emitter legs connected to the base legs of the output transistors either directly or through a relatively low value resistor.

 

[tscr2015]

ok I uploaded a picture from my webcam. The two tall skinny transistors next to the big fat one I believe are the driver transistors and those are the ones that I am having problems with.

 

[Perry Babin]

Did you follow the traces back from the base terminals of the output transistors to the emitters of the next transistors in the circuit?

 

[tscr2015]

The base terminals of the output transistors go to the emitters of the differential amp transistors C3198's and KTB 1369,s. I believe that all of these need to be replaced and also the driver transistors and a couple of small resistors (47ohm) that they(the drivers) are connected to. That Should bring it out of protect mode right. If the drivers are not properly connected to the rest of the circuit i.e blown resistors, would that cause it to go into protect mode?

 

[Perry Babin]

Are you sure that you're using the correct terms? The differential amplifier is typically 2-3 stages back from the output (differential amp >> voltage amplifier >> drivers >> outputs).

 

[tscr2015]

Let me check things out and I will report back