Amp Repair Help Needed...PG Ti 1000.2

[stonedge]

Hi guys, Just picked up a new Tundra so I've decided to throw some gear sitting around the house into it. Ive been out of the game for a while so getting back in I could use some help.

Right now I have the PG Ti 600.2 + 1000.2, PG Ti EQ 30, PG Ti 6 elite (tweeters blew ) for rearfill probably, and Dynaudio 240 GT's for the front. Anyways to the topic at hand...

The amp goes into thermal protection within 30 seconds of being on and does not play loud. With the case removed a hissing/whining noise (not the fans) can be heard in the front right corner of the amplifier. The item in the picture #1 listed T2 has a slightly discoloured, burned look compared to the part listed L2 (on the left) and a slight burning smell was emitted in this region.

I haven't removed the heatsinks to take a look underneath and all the parts look to be intact otherwise. I'd like to fix it myself with a bit of guidance and am willing to throw a dog a bone if someone can help.

I have a multimeter and soldering iron ready for some use. If any other information is needed lmk thanks

[Eric D]

What size fuse is on the amplifier?

[stonedge]

Straight from phoenix gold manual it says recommended is 80A. Where is it though? it's not an external fuse and I cant see anything obvious.

[longboard]

the amps don't have a internal fuse you are supposed to fuse them externally before the amp

[Eric D]

Did you use an external fuse on this amp?

The reason I am asking is I want you to try a 10A or 15A fuse on the amp. If the fuse blows, that tells a lot about what the amp is doing.

Since this amp has a very big power supply, I would guess it is possible the output stage could be shorted, and the supply would feed enough current to heat it up very fast, thus thermally shutting down the amp.

[Jacampb2]

I'm w/ Eric. Likely a shorted or leaky output transistor. Whatever you do, don't keep powering it like it is. Try the low current fuse as said. If you keep messing with it un-fused, you are going to eventually loose one or both power supplies.

From what I have noticed, the high pitch whine is a typical symptom of something drawing very high current on the secondary side of the transformers. It is actually the switching frequency of the PWM moving down in the audible range-- the only time I have heard it is when there is a shorted FET in the PS or a shorted or leaky output, or one time when someone subbed the wrong pre-driver bipolar pair for the PS fets in one amp...

Later,
Jason

[stonedge]

I have an inline fuse on my power wire, 100A. When the amp shut off a year+ back I pulled it out of the vehicle and it sat on the work bench til a couple of days ago. I bought a new Tundra so I want to throw some gear in it.

I just wired in a 15A fuse and it blew on power up.


I know it's not much and not why people come here but I will throw a $50 paypal fee to whom ever helps me through with this...or split it. Far cheaper than me sending it away. Thanks for the help so far everyone.

[Eric D]

Well, to start off, your amp has surface mount components. This means it is a pain in the ass to work on. This does not mean it can't be done, just it is a lot harder.

Maybe Jason will agree, I think your next step is to pull the heatsinks off of the side of the amp which is causing the problems, and then posts some photos of the board so we can point you in the right direction.

[Jacampb2]

I concur Doctor

I would not necessarily limit myself to the side the whine is coming from though. If I recall correctly, the two PWM drivers are slaved w/ the master on the battery terminal side supply, and the slave on the far left side of the amp, so it is possible for one supply to cause issues w/ the other. I had a 1000.2 come through that had a totally baked left hand supply, and the amp would still power up in protect, but the master PWM whined like a little bitch.

But yeah, If you find no blatant physical damage once you pull the sinks, then I would start with the output transistor pairs. If a power supply FET failed, they normally go quite violently, and take all the parallel devices and their gate resistors as well as sometimes the pre-drivers and the PWM IC w/ it, most likely you're going to know if it was in the power supply just by visual inspection.

BJT's are easy to check for good/shorted w/ just a volt meter, you will have to pull them one at a time to check them though. Google how to meter check a Bipolar Junction Transistor. If you find just one of a pair to be shorted, my advise is to replace it and it's compliment. If you really want to do the job right, then replace all the output BJT's on the side that had a bad one. When one shorts or gets leaky, it puts a lot of strain on all of the parallel devices.

FET's are more difficult to check w/o the proper equipment, but like mentioned above, they are normally visually obvious.

L1/L2 are noise chokes/ current limiting inductors. T1/T2 are the PS transformers. It is not unusual for the transformers to discolor as they produce a fair amount of heat while doing their job. Worse case scenario is that you have a shorted winding in the secondaries of one of the two transformers, if so, you ought to hope and pray PG has spares, it is no fun to try to rewind them. Eric is the only person I know of who has rewound a PG one by hand...

Good Luck,
Jason

[Eric D]

That sounds like a plan to me. I have never even seen one of these amps in person, so I really have no experience with them.

[Bfowler]

from recent experiencing i can tell you...picking up a soldering iron if you dont have experience with surface mount wont do anything good for your amp

i just had to send a headunit to eric to fix my ambitious screwups

[Jacampb2]

That sounds like a plan to me. I have never even seen one of these amps in person, so I really have no experience with them.

They are just a mono version of the 600.2, one amp mirrored from the other and on one big board. Each side is almost identical to one 800.1, except they lack one pair of outputs and about +/-15VDC on the rails. The inductors are also specific only to the 800.1, 1000.2, and 1200.1.

Later,
Jason

[stonedge]

Here are the pics with the heatsink off. Nothing really stands out, no burn marks on the board either

[Eric D]

To start, look at the photo I just messed with.

The smaller transistors are for the power supply. The larger ones are for the outputs. Start probing them with your DMM in resistance mode. Look for something that does not belong.

It is really hard for me to explain this with just text here, but your goal is to find one or more of these devices which does not measure the same as the ones next too it. Since each has 3 pins, you have 6 ways of checking it (swapping the leads is the other 3). Does this make sense?

Also, in case you were wondering, do all this testing without having the amp on or anything plugged into it.

[Eric D]

Sorry, forgot the photo...

[stonedge]

K im testing things out right now and am noticing that on certain rows of transistors the impedance does not settle when measured. For example, the large transistors measuring pins one and two at 200k on the top left set of 4 measures .08 consistently. On the bottom left 4 it measures say 1.1 but keeps going up and doesnt stop (1.1, next second its 1.3, 1.5, 1.9, 2.2 etc)

top right starts at 55ish and goes up the same rate and bottom right all 4 start about 42 and continue up. Is this supposed to happen on certain transistors, increasing resistance with the probes applied?

The smaller transistors...I'll test out certain pins and they will remain constant at about 10-12. Others I will test (1) at 1.1 and it will continue to go up to say 1.8. I'll test the next one (2) and it will start at 1.8 and go up to say 2.0. I'll then pull it off and try the first one (1) that tested 1.1 and it will now start close to 2 and keep going up. Frustrating...or is this how its supposed to be?

[waynehead]

Shows how much i know I thought you were checking mosfets

[Bfowler]

mosfets are metal–oxide–semiconductor field-effect transistors
so you were right

[stonedge]

frustrating but fun yarg.

[waynehead]

my stupid is hanging out again

[Jacampb2]

Those big output transistors are BJT's, not fets. Their part numbers are 2SC5200 and 2SA1943, look up the data sheets on alldatasheet.com. You want to measure resistance from emitter to collector, then reverse the probes and measure from collector to emitter. I still recommend you remove them from circuit, the series/parallel resistances in circuit w/ the transistors can throw your readings off. Normally when a BJT fails, it shorts emitter to collector. You normally don't get a short from base to collector or emitter, but depending on if it is PNP or NPN it will conduct from base to collector or emitter, this is normal. Your are mostly worried about collector-->emitter or emitter-->collector.

As for the fets, the reason I said it is difficult to meter check them, is that the meter open circuit voltage that it uses to measure resistance can enhance the FET. Fet's are voltage mode devices w/ typically very low gate capacitance, and if all the leads are not connected when you test, just applying voltage to the drain/source junction can be enough to cause the gate capacitance to charge and the FET to switch on. You will see this as a steady decline in resistance if it switches on and a steady rise if your meter polarity causes it to switch off. There are dedicated instruments for checking fets, but you can rig something up with a 9V battery to enhance the fet and then measure resistance from drain to source. It should be near 0 ohms when fully enhanced. If I recall correctly, before I bought the instrument I used to use a 9V, - lead to source and + lead to gate, then measure resistance from drain to source, it should be 0. Reverse the 9V polarity and it should switch the fet off. Measure resistance again and you should have a very high resistance, above 1Mohm. If you measure source to drain instead of drain to source, most FETs will always conduct because they have an internal "freewheel" diode that always conducts in teh reverse direction. Again, you have to remove them to check them with this method.

I'd concentrate on the BJT's for now. Likely the bank that was reading .08 Ohms, if that was a emitter-->collector reading, then there is probably one of those four in that bank that is shorted. Worse comes to worse, desolder and lift the center leg of each of those transistors in that bank, one at a time and see if the amp still blows the low current fuse. When you find that it powers up fine with one lead lifted, you've found your culprit.

DO NOT, under any circumstances apply power to the amp w/o the heat sinks on the power supply fets, you will cook them in short order if there is still a high current draw in the amp.

Later,
Jason

[stonedge]

Thanks guys. Jason, I'll check them out probably tomorrow and get back to you soon on that. Family friends in town + 12 hour shifts + 3 year old = very little time for toys these days

[stonedge]

alright...had a bit of free time today and should have some tonight. I pulled the middle pin on the bank of 4 reading a constant .8 and tested each one with the pin up, every time blowing the 15A fuse I wired in. Can you guys tell me what settings on my multimeter I should use and exactly which pin placement I should be probing...i.e. + lead to #1 and - lead to #3 etc. I jjust want to make sure I'm testing everything right. Also, an other suggestions appreciated as now I'm stumped