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Old 1st April 2010, 09:13 PM   #7621
alazira is offline alazira  United States
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Quote:
Originally Posted by bobodioulasso View Post
Am i mad to use expensive screw terminal caps 7mohms ESR?
I don't think so. Spending $$ on caps is probably more effective than some other things like RCA's or power plugs.
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Old 2nd April 2010, 01:17 AM   #7622
tinitus is offline tinitus  Europe
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Hmm, big caps with screw terminals are very good to use in heavy duty amps
I have also thought that its better to use big sized cans with classA
That the bigger can results in more cool caps, but Im not so sure about that now

With this low voltage you can get quite big capacitance in a smaller package, and a lot cheaper
And besides, tho screw terminals are good for high current they are far from ideal
Maybe also consider if the involved alu and copper oxidate

Im interested in another matter, namely to build the supply caps into their own "housing", inside amp box, to shield them from the worst heat
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Old 2nd April 2010, 08:51 PM   #7623
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Hey guys, I'm still having issues on my second set of boards. My one 0.47R power resistor is getting 0.5VDC through it, and as a result smokes when applied to wall power. The bulb limiter dimmed very lightly with just that board connected. The trimpots where all set to 0 (even though they are installed backwards) and this is confirmed from R3/4 at 0.3R.

I'm also receiving 12.4VDC for V- to gnd at the boards, and 14.3 VDC for V+ to gnd at the boards. I thought this was normal, since it adds up to around 24, but after reviewing the schematic it should be +24 and -24. My secondaries on my xfmr are 18V, and i'm using normal bridge rectifiers (which may have gotten effed up when i swapped V- to GND)

Another point to make: with no boards connected the light flashed, dimmed down, and went completely out. With both boards connected it flashed, dimmed down, and then slowly ramped up.

Does anyone know what's going on here?
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Old 2nd April 2010, 09:00 PM   #7624
cviller is offline cviller  Denmark
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The bulb in series eats up some of the voltage, so +/-14V sounds reasonable. The behaviour with flashing is also normal as the cap bank draws a lot of current on turn on.

What is the voltage over the other 0.47R? If you have the correct resistors, they do not smoke when 0.5V is applied - there is something fishy about that measurement.

You could post a series of detailed pictures of the amp - this could give us a clue on what might be wrong.
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Old 2nd April 2010, 09:09 PM   #7625
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The 0.5V was taken with the bulb in series. The other three 0.47R were reading 0VDC with the bulb in place as well. I can take plenty of pictures. I'll have them loaded in a little bit.
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Old 2nd April 2010, 09:12 PM   #7626
cviller is offline cviller  Denmark
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WARNING: If one .47 is 0.5V and the others are 0V you need to go back and start over. Turn back the pots to 0 ohm and do small adjustments on BOTH pots.
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Old 2nd April 2010, 09:16 PM   #7627
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Hi.Has anyone tried double 2sk1529&2sj200 with F5 version 2 board?I am interested how it sounds
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Old 2nd April 2010, 09:18 PM   #7628
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they all read 0.3R, the pots are reversed but they were all the way CCW (technically minimum) does this matter?
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Old 2nd April 2010, 09:30 PM   #7629
udailey is offline udailey  United States
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He is saying to check the voltage across the .47R resistor, not the resistance.
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Old 2nd April 2010, 10:32 PM   #7630
cviller is offline cviller  Denmark
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Quote:
Originally Posted by acold7dusta View Post
they all read 0.3R, the pots are reversed but they were all the way CCW (technically minimum) does this matter?
No that makes no difference. But if you have them turned down to zero ohm and you get voltage across the resistor anyway, then you have a short somewhere. I good place to start looking is your power fet mounting. You might be running the current directly to chassis gnd.
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