Phoenix Gold Phorum

What's up Phoenix Phorum? I am new here, and just registered today, however I have been reading the forums for a little over a month now. I picked up two separate PG Tantrum 500.2's on two separate deals on ebay. One worked and came with original birthsheet, box, even the unused sticker. Got a great price too! The other I picked up for $50, the seller said it was on his repair shelf for a year and didn't have time to fix it. Also said that there was a piece of burnt etching that a simple jumper wire would fix. Upon receiving the dead amp, I opened it and went right to the burnt etching....... only to find that someone had already soldered it then removed the jumper (found traces of solder at each break point.) So I jumpered it again, didn't work. Pulled the board, found about 6 blown mosfets, indicated by cracks underneath. Found and replaced 6 burnt 30.1 1% resistors, one coming from each blown fet. Also found that the blown fets were "suitable equivilants". At this point I decided to open my pretty new, well taken care of working 500.2 tantrum. I didn't know they were so shiny inside. Anyway, looked at the fets and ordered what I needed to match the dead amp to the working one. Also looked at the resistors on the good amp so I could actually read the bands. All ordered, all came today. I soldered it all in and it didn't smoke, powered right up. Sadly, It puts out very little sound on either channel, even less bridged (which I find odd). By very little sound I mean I have a home theater satellite speaker hooked up to it, turned all the way up and have to put the speaker up to my ear. Just for the sake of checking, I hooked up my other amp to the same config, volume down, and it works great. Also destroys my car pushing my two jl audio 12w0v2's. Looked at the board for more blown parts and found just two fat resistors on either side of the board (by each channel) that the joints were very eroded and the solder had completely lost connection. The resistors themselves look great (means nothing, I know). I cleaned them up and resoldered them thinking it was finally over......no change. I'm no whiz, but I have done very well buying broken car audio, identifying broken/burnt/missing components, researching then ordering what I need to fix them. I do this mostly so I can have nice things I normally couldn't afford. I rarely fail (then again, I pick my battles wisely), but I am stumped. I will try replacing those resistors, But I dunno. I repaired my tantrum 200.2 no problem, I love the series. Oh, one more thing- there is a "modification" or bypass that almost looks professional, and I haven't messed with it yet. Doesn't seem like much, since it's a small cap and small resistor. My problem is with the output. I don't even get the "pop" through the speaker when cycling the power to the amp. Both channels are equally quiet, and bridged is a third quieter. I really wanna fix this and bridge each amp and have each one push one of my jl audio 12's, with the amp turned down a little. Should sound great, look great in my amp rack I'm building, plus giving me wiggle room for when I can get better subs. Sorry so long, just wanted to provide as much info as I could. Any help is appreciated.
Thank you.
P.S. I haven't scoped it. I have a scope, but can't seem to teach myself how to use it. Will post pictures when I can convert to a size that the site will let me upload.

Wow. 48 views and no input.

I'm decent @ amp repair, but I would pretty much need the amp in front of me to figure out what's going on. Unfortunately, trying to trouble shoot stuff like this via threads is a pain staking process

Something simple (and one of the first things) to try would be to adjust any and all pots, switches etc and see if the signal comes alive.

Fallen1 wrote:Wow. 48 views and no input.

Hit up Valeks1, he's the local repair tech for PG. His website is http://www.altser.com and all repairs come with a 90 day warranty.

I appreciate that info, but I prefer to do my own work. I enjoy it.

Fallen1 wrote:I appreciate that info, but I prefer to do my own work. I enjoy it.

It's all good ...just throwin' it out there if needed.

I appreciate that. I found two of the four main caps that are bulging a little. Maybe that well help. More parts order waiting *sigh*

Odd, noW the amp wont turn on and it melted my ground wire....... Positive lead got a little warm, but that's it.

Here are some suggestions which may help.

Check all the output transistors and look for any which are shorted. You can use a DMM in diode check to inspect them.

Power the amp on with a 12V automotive head lamp in series with the power wire. This will limit the current, but still should allow the amp to power on for diagnostic purposes.

Look for the rectifier section of the amp, and check to see that it has both a positive and negative voltage preset at the "rails". On that amp, I would guess it is 35V to 40V both positive and negative. This number will be less while powered up through a headlamp, but will still be significantly higher than the 12.6V to 14.4V input you are using for testing.

If you have rail voltages, and you can't find any blown output transistors, you need to start looking around for a failed voltage gain section. I doubt this is the problem though.

Check for DC voltage on the output terminals as well. If you find the same DC as one of the rail voltages, you have some shorted components for certain.

These are just some ideas. There are lots of things to look for, and as previously stated, it is pretty difficult to diagnose an amp via the Internet.

Thanks! That gives me a little direction. I'm great with finding and replacing the blown parts, soldering cracked joints, jumping fried etching- the obvious stuff. The finer details still give me trouble. Checked out repair prices and I could just buy another tantrum for that kind of cash, so I'll play with it in my spare time. My thought is that it is tramping up the voltage somewhere and dumping it to ground since the positive wire was warm while the negative melted.