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Old 29th December 2008, 01:00 PM   #21
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Quote:
Originally posted by Nico Ras
I am curious, how did you test the transistors. Were the light on only when you biased the gate?

I never start with the output transistors connected.
I just send the output back into the feedback loop in the LTP.
That way I know the driver circuit is working first.
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Old 2nd January 2009, 10:15 PM   #22
rtill is offline rtill  United States
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ok, started all over from scratch, new transformer, new power supply, new power amp circuit...same thing, extremely loud hum then blows the fuses right away. I must have something wired wrong.

So is this correct when wiring in the 2sj162 (see attached picture) .....source is on top, gate on left and drain on the bottom?

I wish I could post a picture of my layout, but I can't...it matches the schematic from left to right is all I can say. Does this circuit actually work?
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Old 2nd January 2009, 11:43 PM   #23
rtill is offline rtill  United States
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new finding....
When I put in new fuses, immediately when I put the first one in, my speakers pop. Is this the caps draining from my power supply?
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Old 3rd January 2009, 08:22 AM   #24
AndrewT is offline AndrewT  Scotland
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where is the mains light bulb tester fitted?
It will prevent the fuses blowing and allow you loads of time to take measurements.
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Old 3rd January 2009, 10:07 AM   #25
Symon is offline Symon  United Kingdom
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"tested my transistors with a bulb tester"

I don't think this is what Andrew meant !

I think he means place a large bulb in series with the AC supply.
this acts as a current limiter because it has low resistance when
cold, and high resistance when hot.
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Old 3rd January 2009, 11:49 AM   #26
AndrewT is offline AndrewT  Scotland
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Rtill seems to be one of the " bolt it together and see how quickly I can blow it up" crowd.
So far his lack of research has achieved a lifetime of less than 100mS.

Keep going, I'm sure you can better <10mS.
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Old 3rd January 2009, 05:15 PM   #27
rtill is offline rtill  United States
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all right, stayed up half the night and decided to build project 27b(100 watt mje3055/mje2955) from elliot sound/ westhouse..... works flawlessly. I am convinced that something in my 300 watt mosfet build is just plain wired wrong and I've spent to long on it to debug it anymore. Has anyone else here built the 300 watt mosfet? I am just curious if the mosfets I bought were really Hitachi and the pinouts were correct. I bought them from www.futurlec.com - really inexspensive. Per their site, the mosfets are Hitachi. Could someone post a picture of their 2sj162 and 2sk1058 so I can compare?
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Old 3rd January 2009, 06:04 PM   #28
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Here is one Mosefets under the board.
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Old 3rd January 2009, 06:14 PM   #29
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Default From DIY Turkey

This one was done by Dr. Gokhan Nalbant on a later revision PCB.
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Old 3rd January 2009, 06:33 PM   #30
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You purchased at $1.10 at the on-line store that you mention. This sounds a bit on the cheap side, they normally cost about $ 8 to $10 for genuine Hitachi.

If you have a magnifier, the name Hitachi is written inside the left hand top hole. The markings K1058 and J162 is laser etched onto the housing.

However, even if they were substandard one would assume that it should pass the 250 mA bias current without blowing.

You could try the amp with just one pair of output devices and repalce the fuses with 10 ohm 10 watt resistors or use Andrews light bulb technique to see if all is well before turning the real power on.
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