F5 Turbo Circuit Boards

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nashbap

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Lordi said:
but i don't like two things.
there is not enough space between the mosfets. if the bias is about 0.8 A/output device, and the railvoltage is about 32 volts, it would be about 200 watt dissipation. For this, i need a bigger distance between the mosfets for large heatsinks.
?QUOTE]

Wouldn't you be better off from the standpoint of heat distribution to put all four n or p output devices spread out in a straight line? That way you can mount the devices near the horizontal center of the heat sink for the most even heat transfer.
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Russellc

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Heat sink spacing w/ store 5U and Tea-bag boards

Seems like I remember someone asking if Teas boards can be used on the heatsinks (on the store 5u deluxe chassis box) and the response was (I thought) that some lower holes may need drilled, but otherwise would work.

I am not finding an easy way to equally space the two pairs in my V2, at least not so that the fets line up with the pre drilled holes, and if I jerrymander it to do so, it seems they are not centered on the sink, but closer to the center line
between the sinks.

Do I have to run wires from the fets from the board? How have others mounted their V2 with teas boards to these heatsinks? Should I have just got "blank" heatsinks with no holes and ddrilled myself? Even then, the board doesnt allow me to center the fet and diode in the sinks center area, but closer to the center line between the two sinks.

If anyone has a pic and can tell me what holes had to be added, I would appreciate it greatly. I like Teas boards and obtained them over the store board version. However, after the expense of the case and other turbo doo-dads, I really didnt want to jerry rig this amp. Maybe I'm not seeing the best way to do it, but I am about to conclude that I should mount the board to four of the board mounting post positions, and run short wires to the legs of the devices. Is this a valid way to do it? Surely someone out here has figured this out?:confused:

I dont mind drilling and tapping more/new holes...if I have to. Also, if wires are used, is that sufficient or do some of the resistors have to be move off board and closer to its mosfet? Similarly, the TH1 and TH2...I guess the Fet by the TH parts could be mounted to the board so that thTH part will reach it, and run wires to the balance of the other fets?

Russellc
 
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Russellc

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buzzforb said:
If you want to mount the diodes to the sink, you will have to tap holes. Is this at the core of your question?
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No Buzz, its the centering of the two pair of mosfets....I havent decided whether or not to mount the diodes on the sink or not, no big deal if I do and need to drill holes. If I get one set of two pairs centered, the other pair isnt in the center of the other sink, in fact one is on the wrong side of the sink, and the other too close to that same side....

The core of the question is, how does everyone space them properly, or is it impossible with these boards and leads need be run. If so, does this create any problem with one pair on leeds, one pair not? And if this is the method, do any of the resistors need to be moved off board to be closer to the fets made remote via the leeds?

Russellc
 
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Russellc

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About the best positioning I can find so far, is with the Q10 + Q12 pair located at the holes that are the third set from the crack between the two sinks....this leaves the other pair Q3 + Q5 pair at a set of holes as well, same positioning on the sink, third set of holes from the center crack. This would leave re-drilling and tapping the board stand off holes, (4) and a few if I decided to mount the diodes to the sink. Only problem I see with this is that the pairs are not directly centered on the sinks, but both pairs slightly closer to the center line...maybe at the 1/3 point instead of the 1/2, or center point.

Russellc
 
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Russellc

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Well, tell me...right now they are "centered" not too bad, just not centered. Measuring from the center between the two sinks, ONe pair is about 1/3 of the way in one direction, the other pair about a third of the way the other direction. If they would go 1/2 the way in each direction, they would be centered, so I am not that far off? The center of the two pairs is 4 and 3/4 inches apart.

Russellc
 
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Russellc

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buzz, if you look at the UMS specification drawing, there is a green dot in the center. There is a row of holes going across the sink just below this green dot.
Starting at the center just under the green dot and you count three holes to the right and also 3 holes to the left, these are the positions the Mosfets would be attached to. Is this enough spacing?

Russellc
 

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Russellc

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abadsantos 7 said:
Hi Russ,

Are you open to the idea, by getting a separate piece of aluminum then tap the holes based on your PCB specification? This will give you a complete freedom where you can place PCB based on your preference.

Then mount the aluminum to the main sink using the pre-tapped hole.

Regards,
Click to expand...

Yes I did, but the hole reason I chose this box was so I wouldnt have to do all that fabrication. Otherwise I would have built the case from scratch. I have attached a pic of the proposed positions now. I got to thinking, while the store boards are nicely centered, the fets are not! One is off to the side in one direction, the other to the other direction. I'm calling it good.

The only other thing that would be easier than the spreader, would be to use the short wire leeds. This would also make it way easier to change output fets if they blow...this board is way difficult to remove parts from. Very thick, and the holes fill up like a little well, from top to bottom.

Russellc
 
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Russellc

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buzzforb said:
It's up to you and what you are willing to do, but you could mark off 20mm c to c and position for best dissipation. Perhaps not perfectly centered on sink, but should be fine, heat wise.
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20 mm? Isnt that less than an inch? .787402 inch in fact? I dont think I understand, but I think the positioning I have is OK...if anyone disagrees please chime in!

thanks for the info,

Russellc
 
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Russellc

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henryve said:
Pfft! You guys must count yourselves lucky being able to get cases for little money. It's bush engineering for me.:smash::rofl: Tablesaw, bastard file and drill...
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I did that with my first F-5. I think there are pics in the gallery. Did an B-1 in a similar styled case. Had 6061 aluminum filings and drillings everywhere for months! I'll just have to drill and tap a few extra holes with this rig! building it myself, while much messier was WAY cheaper than these ready built jobs.

Russellc
 
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Russellc

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henryve said:
Pfft! You guys must count yourselves lucky being able to get cases for little money. It's bush engineering for me.:smash::rofl: Tablesaw, bastard file and drill...
Click to expand...

I did that with my first F-5. I think there are pics in the gallery. Did an F-5 in a similar styled case. Had 6061 aluminum filings and drillings everywhere for months! I'll just have to drill and tap a few extra holes with this rig!

Russellc
 
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