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Old 14th November 2012, 02:25 PM   #31
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ok and i think q10 is shorted too right? and should i pull out the transister on the ones that are shorted sence i have to replace them anyways? but the third leg is the ones that are towards the rca right? and do u want me to still check transister Q7 Q7 Q8 Q9 Q10 Q12 Q16 after i pull the third legs out? or checking the other side of the amp transister?
thank you again

Last edited by superjoey01; 14th November 2012 at 02:30 PM.
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Old 14th November 2012, 03:20 PM   #32
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Q10 yes its also bad . Just pull the third leg < towards the RCAs > out of circuit on all the bad ones, and leave one leg attached. The reason for this is when you get new parts there won't be any confusion as to what went where. please check the other side also...
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Old 14th November 2012, 03:22 PM   #33
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Smile recheck with transister out

hi i tooked out the bad one's listed above and recheck here are the results thank you
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File Type: png rechecked with transister out.png (203.6 KB, 22 views)
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Old 14th November 2012, 03:45 PM   #34
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Yes its bad. Any reading below what a normal diode junction would read is bad. So anything below 340 ohms or so is bad. Usually they will read in the 20 ohms or less all the way down to 0.00 ohms. it sort of depends on the quality of you meter somewhat as to what numbers you will get. But number of 340 up to 760 are a normal junction reading.
Your amp seems to have blown all the 2N6490 outputs. Q12 is the driver for those outputs please check it carefully like you did the others it likely is also damaged with all of those outputs being bad. I have a A600 open on bench at this moment so I am comparing your info directly to my unit here
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Old 14th November 2012, 04:03 PM   #35
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K thanks
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Old 15th November 2012, 02:11 PM   #36
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Default here are the reading for the otherside of the amp of transister

hey everyone here are the rest of the reading of the other side of the amp transister. The transister are still in on the otherside, so here are the results
Attached Images
File Type: png Q54 to Q55.png (205.3 KB, 20 views)
File Type: png Q56 to Q57.png (186.5 KB, 21 views)
File Type: png Q58 to Q59.png (164.6 KB, 19 views)
File Type: png Q60 to Q61.png (163.4 KB, 19 views)
File Type: png Q62 to Q63.png (165.3 KB, 4 views)
File Type: png Q64 to Q65.png (179.8 KB, 4 views)
File Type: png Q66.png (137.2 KB, 4 views)
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Old 15th November 2012, 03:44 PM   #37
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Comparing your readings to my known good amp on my bench all of these transistors are reading OK.
So I would concentrate on the other channel as your real problem for now.

Also Q54 & Q6 are not output transistors, They are lower rail pass elements < +&- 15 volt regulators >. These have large voltage drop across them when the amp is powered on so they will get hot and blow out if they are not sinked properly. This is why I work on these in the sink and why this amp must be properly clamped back into the sink before applying power to the amp for testing purposes. Make some U channel clamps like Perry recommends, please...
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Old 15th November 2012, 09:53 PM   #38
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ok so where do i get the stuff to make the clamps? and when i make them what do i do next?
thanks you
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Old 16th November 2012, 12:28 AM   #39
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Ok Perry says use aluminum U channel stock material you can buy at any major hardware store. < just go into Home Depot or Lowe's and ask for tube and channel stock steel or aluminum, it comes in yard or meter lengths >
Myself I use tube steel stock with some pad material glued on the transistor side. I use tube steel stock because it does not bend or flex distort, and my clamps are tool fixtures that get used again and again. Mine are old now but they have been thru dozens and dozens of amp repairs. I also use my clamps to power test and align the amp without the bottom on the amp so mine get lots of wear and tear over the years. U channel stock will work but I chose to use tube steel stock instead.
It's your budget so you decide which material and how much you want to spend for your one or two time use of the clamps. I went overboard on mine due to the usage factors they get on my bench. PPI is the only amp made that requires these clamps. You have two amps so I would go light with aluminum, as you will likely throw them away after your done anyway....

Once you have the material you must cut it in functional lengths to accommodate the amps your working on so they cover all the power devices with there clamp pressure. And you must drill holes to allow you to use the sink screw holes to tighten them down in place clamping all the power devices against the sink with some fresh silicon heat sink compound in between the transistors and the mica insulators and the sink. Once you at this point you can test the amp with power applied and not have to worry about any heat related failures due the power devices not being pressed tightly to the sink frame.

You can replace the bad outputs once you have the above clamps made and ready to install. Once replaced you can clamp the assembly together and apply power and turn on the amps. I suggest a 3 to 5 amp fuse inline with the power just to be safe and careful not to damage anything just in case something was overlooked and or missed....
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Old 16th November 2012, 12:46 AM   #40
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so i need to buy parts and silicon heat sink compound. where do i get the heat sink compound and do u know what the part numbers are?
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