ppi a 600.2 hurtin, please help gurus - diyAudio
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Old 8th March 2007, 08:30 AM   #1
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Default ppi a 600.2 hurtin, please help gurus

I have searched and found some other threads involving this amp with similar issues.

I uploaded a video on youtube so that you can see what is happening

youtube video of my problem click here

if you can't see the video, here is a short description of what is happening:
my set-up is a Kenwood deck, alpine parametric eq for the bass, 1 fosgate hx2 10" DVC 4ohm in series at 8 ohm wired to the amp as bridged. I switched it to parallel (2ohm) wired bridged and the same thing happens

at low volume it sounds good, as I turn up the volume the bass will come in, but there is a point at witch the bass starts to cut out and distort and the low ohm light starts to flicker. As I turn up the volume the light flickers more and more brightly the louder I go and the distortion gets worse and worse.

The amp puts out some serious heat even at low volume, to hot to touch even, seriouly it would burn you. I don't have a temp, but I would geuss up in the 170-180*F

If I had to guess I would look at the resistors at R153 and R154 on the board, they look a little burnt and off color from the others in that row.

I appreciate your help

Ken
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Old 8th March 2007, 01:38 PM   #2
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Location: Louisiana
It looks like the transistor connected to the two resistors has shorted (or all 4 of the others opened - unlikely).

Remove and check that transistor. If it's shorted, you'll need to replace it and the other 4 running in parallel with it.

If it's shorted, you can play the amp without it to see if it gets hot (no load, no signal). You MUST replace the bottom cover and tighten the bottom cover screws before powering up the amp. If the amp runs cool, there may be no other problems.

Since this sort of problem causes extreme stress on all of the output transistors in the channel, I'd suggest replacing all 10 of the outputs. You'll also need to replace the emitter resistors. I'd suggest replacing all 10 shown. The others are likely OK.
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Old 8th March 2007, 04:59 PM   #3
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If you look at the picture, the resistors are a different color than the rest in that row(the bands around it), they also spec out alot higher resistance than the others. the other resistor in that row are a .5 ohm and I think these 2 spec out to be in the 700ohm area(i'd have to check again to be sure of the numbers)

I'm not as inclined in the "solid state" electronics as I'd like to be, so how do I check for a short on a transistor?

I have ohm'd out all the transistors on the board and they all seem to match each other repectively to the corrosponding part number printed on it.

thanks for you help Perry Babin,

Ken
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Old 8th March 2007, 05:34 PM   #4
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The resistors can change color when they overheat. If there are 5 sets of resistors (of the same color) on the other half of this channel, the discolored ones should be the same as the other 8 in this half of the channel.

Check for zero ohm (or near zero ohm) connections between the terminals of the transistor connected to the discolored resistors. If any combination is near zero ohms, the transistor is likely defective. Pull it and recheck it out of the board.

With the transistor out of the circuit, if you get anything other than an open circuit reading between terminals 2 and 3, the transistor is leaking and therefore defective.

For initial testing in the board, you can set your meter to ohms or diode check. When it's out of the board and you're checking for leakage (assuming it's not completely shorted between terminals), set your meter to ohms.

You should check the other transistors in that channel also.
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Old 9th March 2007, 09:08 PM   #5
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you help is much appreciated!

I'll let you know how it pans out
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