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Old 25th July 2007, 01:56 PM   #11
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Join Date: Oct 2005
Is it safe to assume that there are 12 power supply FETS? Two of them have clear markings of IRFZ46N. Would all 12 of these components in the bank be identical?

Thanks.
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Old 25th July 2007, 05:10 PM   #12
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Location: Louisiana
There are 12 power supply transistors. They are all the same part number.
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Old 6th August 2007, 03:29 PM   #13
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Wouldn't you believe it, Soundstream sent me the schematic for my amp. I am so excited.

I brought the amp to work today and will be removing/testing all 12 ps fets and gate resistors, 8 output transistors, and any other T0220 chips that I might have damaged while removing the compression clips.

Thanks for you help so far. I will update again when I replace all of the components and test.

I do have one question. How would you go about testing the amp? I was thinking about bench testing it with a current limited power supply as to not have the large current draw from a car battery. Would this work or would it hurt any of the components? It seems like this should work, but is there a low current limit that the amp needs to function?

Thanks again.
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Old 13th August 2007, 06:56 PM   #14
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I did some more reading and found that some people test using a 2 ohm resistor in series with the power wire. That seems like a good idea only it may be difficult to find a resistor with that power handling.

I have another question. There are a couple TO220 packaged components that I am trying to locate alternatives for so that I can order them. Does anyone know alternatives for the following parts:

voltage regulators
KIA7815
KIA7915

Ultra fast recovery diodes made by sanken
FMG22R
FMG22S

Thanks.
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Old 13th August 2007, 07:23 PM   #15
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Location: Louisiana
The following devices are not fully encapsulated so you need to use insulators under them. Digikey has all of them in stock. The regs rarely ever fail. If the rectifiers fail, it's generally a mechanical failure (broken leads).

voltage regulators
KIA7815 >> L7815CV
KIA7915 >> L7915CV

Ultra fast recovery diodes made by sanken
FMG22R >> MUR1620CTRG
FMG22S >> MUR1620CTG

If you are ordering parts, you can order the resistors. 50 watt is the minimum wattage I'd suggest. 100 watts will run cooler and can be used as a dummy load. I use a 25 watt resistor but it's fan cooled. Use the tubular ceramic type. Their power rating is not dependent on heatsinking like the aluminum type.
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Old 14th August 2007, 04:12 PM   #16
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I placed the order for the following items:

12 - power supply fets
8 - audio output transistors
4 - diodes
1 - voltage regulator (couldn't get the other one)
1 - pwm controller

I purchased extra supply fets in case the amp blows again. I found a set of resistors at work that are 275 Watt power handling and variable resistance.

My desolder job on the board was not the best. I broke a couple solder holes, so I will have to make a bridge with solder for those connections. I am looking forward to getting my order and testing the amp.

Does anyone know if there is a minimum amount of current that the amp needs to startup/run?

Is there a trick to the compression brackets that hold the TO220 packaged components to the heatsink?

Thanks.
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Old 14th August 2007, 05:39 PM   #17
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Location: Louisiana
Were all of the gate resistors for the power supply transistors within tolerance?

Did you check the gate drive at the power supply FETs to confirm that you don't have any drive circuit problems?


You can't bridge with solder alone. Scrape the solder mask from the trace leading to the damaged pad and tin it with solder. Use the lead from a resistor or similar piece of wire and bend it so that it has a loop to go around the transistor lead. Solder it to the tinned trace. You want to have enough of a lead on it so that it provides a solid mechanical connection to the board. The steps are shown on the following page:

http://www.bmpt1.com/temp/repairtrace01.html

If there was a via that connected a top trace to a trace on the bottom of the board (or vice-versa), you need to make the same repair on the other side of the board.


The 'tool' at the top of the page is what I use to re-seat the clamps. It's a 5/16" nutdriver with a piece of 6g wire insulation in the tip. It's not fancy but it works very well. Use a pair of pliers (crimping pliers work well) as a hammer. You don't want to hit the the clips too hard because they can crack. Just tap them until they bottom out in the groove.

Use a 10 amp fuse in the power line if you don't have a current limiter. It won't run at full power but you'll be able to check the power supply function and audio (at low power).
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Old 14th August 2007, 06:23 PM   #18
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I pulled the first two gate resistors and they were fine. I then tested the rest on the board and they all read the same (~100 ohm I believe).

None of the Via's that I broke connect the bottom to the top of the board (thankfully).

Thank you for the excellent pictures of how to repair a trace. I had planned on doing a similar process, except the via's that I broke are directly connected to a large power plane. This will make the repair process easier.

I have not tested the drive circuitry yet, but will be doing so soon. Since the ps fets are removed from the board, the only part that I can check is the pwm controller and push/pull transistors that are right before the ps fets. This will be a good test to know that nothing before the ps fets are bad, before I replace them.

I truly appreciate all of your help. I have never found a forum where the people are so intelligent and willing to help.
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Old 20th August 2007, 02:37 AM   #19
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I replaced all of the TO220 parts and tested the amp. Using an old 8 ohm subwoofer, the amp seems to be running strong. I will be testing the amp at 4 ohms tomorrow and hopefully will not find any problems.

Is there any reason to believe that the amp will not work at 4 ohms when it works at 8 ohms? The amplifier is 1 ohm stable so I wouldn't believe the jump in power between 8 and 4 would be great enough to cause problems. I guess we will see. I plan to run the amp at 1 ohm sometime in the future, so hopefully there won't be any stability issues.

I am so excited!!

Thanks for all of your help. If anyone wants/needs the schematic for this amp send me an email and I can email it to you.
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Old 20th August 2007, 08:25 AM   #20
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Location: Louisiana
If it works into an 8 ohm load, it will likely work in to the lowest rated load with no problems.

Be sure to clean the heatsink and insulators. Make sure there are no metal splinters/shavings on the insulators or heatsink. Apply new heatsink compound to all mating surfaces.

When you power it up and run it hard, monitor the temperature of the transistors (touching the clamps is good enough). If any are getting hotter than the rest, you may have a problem. Most all should run relatively cool.

When you run it into a 4 ohm load, you may want to reduce the total fuse rating to ~1/2 of the normal fusing. If it has four 30 amp fuses, go down to four 15 amp fuses. If you blow the fuses, replace the blown fuses with a single fuse. If the single fuse holds, the four 15s may not have been enough (they should be at 4 ohms). If the single fuse holds and the amp powers up and plays (at low volume), the amp should be OK and you can go back to larger fuses. Using the single fuse to test the amp after it blows fuses will help prevent additional damage if there is a problem.
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