# Help me figure out what's wrong with my amp. Video included.



## schmiddr2 (Aug 10, 2009)

Amplifier is a Phoenix Gold Titanium 500.4
I tested it today and it seems to have a bad channel. 3 of the channels sound great and 1 sound like it has lots of distortion (especially when there is more bass in the song). Watch the video below; I test a good and the bad channel. Amp was set to full range and speaker used was a eclipse sp6510; no enclosure but shouldn't make a difference. Please help me determine the problem and find a solution. Thanks

http://www.youtube.com/watch?v=mzFOEOBuays

The amp


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

wow, have you swapped the L/R RCA to see if it moves with the RCA or not?? 

If it doesn't move, you lost something inside the amp, unless you have the gain out of whack or something..


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## schmiddr2 (Aug 10, 2009)

Aaron'z 2.5RS/WRX said:


> wow, have you swapped the L/R RCA to see if it moves with the RCA or not??
> 
> If it doesn't move, you lost something inside the amp, unless you have the gain out of whack or something..


I tested both L/R RCA. The gain and crossover were the same for both tests. The channel in question is the rear left channel (Picture). All the others work fine. If it is blown how do I go about fixing it? I'm handy with a multimeter, but I have no clue what to test and what values individual components should read out to be.


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## schmiddr2 (Aug 10, 2009)

Anyone else? I just need some idea of what to do next. What components can or do cause this type of channel separated distortion?


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## schmiddr2 (Aug 10, 2009)

Well, as usual I cannot stop reading when I have electronic issues. On the PG forum I have discovered that a lot of people have had a similar issue.

They say it's this: "This is a notorious problem for the ZX475Ti/ Ti500.4. The potentiometer pots on the amp cause problems (Variable crossover pots). Try working them back and forth to see if they clear up."

And: "...sent a email to Alexk(tech who works on the amps @ PG) and he suggested turning the pot back and fourth twenty times; he states they build up resistance, overtime..."

If this is my issue it does not seem like a big deal. I will test it tomorrow.


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## schmiddr2 (Aug 10, 2009)

*UPDATE*

I have been talking with the guy from bcae and a guy from PG tech support. We have narrowed it down to the output stage for the bad channel. It had 2 LED's out for that channel. PG tech said:


> Your video and photo indicate that the negative half of the output stage on the malfunctioning channel is not operational: you're only getting the positive half of the audio waveform. There are a number if components in the Ti500.4 which could fail and yield this result: some careful work tracing the amplifier signal flow with your scope will be required to identify the root cause. We can probably supply parts you will need to repair this product at a reasonable cost.





> Since LEDs D102 and D104 are not properly lighting, focus on the first half of the component list. D102 and D104 are in the current path of R129, Q109, Q110, Q111, Q108 and R124.


 D=LED, R=resistor, Q=transistor

Here's a picture of the oscilloscope test of a good channel








And the bad channel









I'm hoping to remove the bad channels transistors and do the test as shown here: http://www.bcae1.com/repairbasicsforbcae1/images/transistortestpage02.html


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## 60ampfuse (May 18, 2008)

Ahh that sucks man, are you going to attempt to fix it or just use it as a 2 channel? You cant even bridge the rear channels if one of the negative rails is bad


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## schmiddr2 (Aug 10, 2009)

Fix it. I will unsolder the transistors, test them, replace the bad one(s), and then put it back together. It does suck; 2 channel will not work for my build so I must succeed.


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## TREETOP (Feb 11, 2009)

schmiddr2 said:


> Fix it. I will unsolder the transistors, test them, replace the bad one(s), and then put it back together. It does suck; 2 channel will not work for my build so I must succeed.


That's true DIY spirit right there, props! Hopefully you can tackle it pretty easily.


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## jrgreene1968 (Jul 7, 2008)

good luck man..hell with my luck, id try to fix it and screw up the other 3 channels.


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## schmiddr2 (Aug 10, 2009)

I need some more help. I have been talking with PG support and they are great! They informed me of which transistors are in the path in the bad channel. Now I have removed 4 of them and am not sure if I'm testing them correctly!!! How do I go about testing them? I have an DMM and oscilloscope.


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## chad (Jun 30, 2005)

You need to use the diode test function of your DMM

Pas/Fail transistor testers rock too


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## 240sxguy (May 28, 2009)

You need to lookup the datasheet for your transistors to figure out which legs are which, then do a google search on how to test them. Odds are your dealing with an NPN or a PNP transistor. They are tested using a multimeter as chad said. 

Evan


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## chad (Jun 30, 2005)

Chances are the finals are fine and you have an open drive transistor, it could be as much as an open leg on a drive transistor too! Does that channel run warm/hot? Bias is applied thru the drive transistor. If oyu have an open side of drive it will sound like that because it only makes 1/2 of the waveform, it will be ****ty and WAY down on volume. I have seen it as simple as a busted leg on a transistor from vibration, take a pick and gently pull on the legs.


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## cubdenno (Nov 10, 2007)

I would just send the thing to ZED. He fixed my MPS2240. I thought about fixing the thing or rather attempting it and figured my time and parts with the potential for tragedy was way more expensive than getting it done. No offense to your DIY spirit.


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## schmiddr2 (Aug 10, 2009)

This is the wave form









The board, (left section is channel 4 bad channel)









Specifically the PG tech guy said "Since LEDs D102 and D104 are not properly lighting, focus on the first
half of the component list. D102 and D104 are in the current path of R129,
Q109, Q110, Q111, Q108 and R124."


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## chad (Jun 30, 2005)

schmiddr2 said:


> This is the wave form





chad said:


> If oyu have an open side of drive it will sound like that because it only makes 1/2 of the waveform, it will be ****ty and WAY down on volume. I have seen it as simple as a busted leg on a transistor from vibration, take a pick and gently pull on the legs.


Shazam, negative drive is open.


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## cubdenno (Nov 10, 2007)

chad said:


> Shazam, negative drive is open.


Show off!!!


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## chad (Jun 30, 2005)

sure would be sweet if it was a busted transistor leg!

Hopefully when I said take a pick, he did not take me as saying take a pic. LITERALLY remove power, take a PICK and tug around gently on the driver legs. 

Hint, transistors don't GENERALLY blow open, they CAN, but not generally. Resistors will however


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