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Old 18th July 2012, 08:35 PM   #2041
BigE is offline BigE  Canada
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Is there any issue with adding wiring so that the mosfets reach the heatsinks?

I've only seen designs that have their heatsinks bolted directly to the mosfets that are soldered to the PCB. My enclosure will be just wider than 90mm to accomodate the transformer.... Other designs have shown the mosfets bolted to the base plate of the enclosure -- are they hotrodding like that?
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Old 19th July 2012, 07:22 AM   #2042
brainf is offline brainf  Philippines
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Quote:
Originally Posted by BigE View Post
Is there any issue with adding wiring so that the mosfets reach the heatsinks?

I've only seen designs that have their heatsinks bolted directly to the mosfets that are soldered to the PCB. My enclosure will be just wider than 90mm to accomodate the transformer.... Other designs have shown the mosfets bolted to the base plate of the enclosure -- are they hotrodding like that?
Mine are wired with short lengths of magnet wire. No problems

Last edited by brainf; 19th July 2012 at 07:24 AM.
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Old 19th July 2012, 10:48 AM   #2043
BigE is offline BigE  Canada
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Thanks! I'd guess the only issue would be potential for noise, especially with stranded wire.
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Old 19th July 2012, 02:11 PM   #2044
Salas is offline Salas  Greece
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That is oscillation potential territory. Extending is adding inductance, at least solder the gate resistor with very short pin to the gate -after- any attempted extension cable, and restore continuity with a jumper where the resistor was on PCB. Was not intended like that, nor scoped like that, grey zone.
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Old 19th July 2012, 02:54 PM   #2045
BigE is offline BigE  Canada
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Thanks!

The issue for mounting monster heatsinks and transformer in a box are mechanical --the 80 va transformer is over 90mm wide and bending the pins on the mosfet is not enough to make them reach the sink with a box that is 90mm wide internally.

So, instead of fins sticking out from the surface of the box, the box can be made larger by making the fins flush or in the same plane as the sides of the box. The footprint of the enclosure can be thought of as a barbell or dog-bone. The heatsinks may be bolted directly to the floor and become the middle front and back side of the enclosure.

One end now has enough room for the transformer.

--------------------------------------

If the pins of the mosfets can be bent to reach the heatsinks which are at the sides of the board and bolted to the top/bottom of the enclosure, then all problems are solved.

If the pins can't be bent, then a thick 10mm aluminum bar needs to be added as a heat spreader, though I worry about the thermal efficiency losses.

Last edited by BigE; 19th July 2012 at 03:01 PM.
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Old 21st July 2012, 02:17 PM   #2046
Siberia is offline Siberia  Lithuania
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Default it's back and not kicking

No rest for me. I'm experiencing something I can't grasp control off. Low frequency attenuation is back three months later after the fix. It's a recurring problem, that was curred in different ways earlier. This time I'm more certain it's a DCB1 problem. A passive, two mono attenuators based pre shows more slam and bass and overall better balance in lows.

Checking connections, soldering, usual procedures since yesterday.
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Old 21st July 2012, 04:46 PM   #2047
Siberia is offline Siberia  Lithuania
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You wouldn't guess what has worked for me. Cleaning both sides of pcb. I live in ex industrial area and building. It's quite dusty here and the pre was still in an open case. The underside collected dust as it was sticky after cleaning with isopropyl alcohol from last time. Wiped good as I could and voila.
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Old 21st July 2012, 04:48 PM   #2048
Salas is offline Salas  Greece
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Old 23rd July 2012, 07:25 PM   #2049
BigE is offline BigE  Canada
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Picked up the transformer today! Potted 80 VA from Sumr in Toronto.

Now to order the heatsinks and the rest of the parts. Then, either make a box -- or stuff it into rectangular aluminum tube, a la Peter Daniel.

heatsinkusa looks like the best source.
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Old 23rd July 2012, 08:03 PM   #2050
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Quote:
Originally Posted by BigE View Post
Picked up the transformer today! Potted 80 VA from Sumr in Toronto.

Now to order the heatsinks and the rest of the parts. Then, either make a box -- or stuff it into rectangular aluminum tube, a la Peter Daniel.

heatsinkusa looks like the best source.
80VA for a DCB1? A bit big. I believe that ~25VA is sufficient. Anyways, it can't hurt if you use the right fuse!

Do
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