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Mario

Thanks! I may call on you for these.

In the meantime I have established the board is OK, and that the GG1 won't pull squat with only one motor driving one truck, and the other truck totally free wheeling.   I have also established the Kohs pickups are quite a drag.  And they are on both sides.  Not a good design.  I partially addressed that, and improved the run time.

I am currently pursuing two options

1)  Go to more efficient motors (my original course).   My goal is to get below 1 Amp, where I know it will run for a long time.

2)  Put a second PS 3 board to drive the second motor and run the whole thing as a Lash Up. Per Pat's suggestion. Space is a challenge, but we'll see

Your fan gives me a third.

Incidentally, I considered dunking the board in a thick copper mini bath tube of fluorinert.

https://www.3m.com/3M/en_US/p/d/b40045180/

Would have solved the problem.  But sealing against leaks would have been a challenge.

John

I'd be looking for more efficient motors, but I'd think the Pittman's would be pretty good.

Have you considered dropping in a different PS/2 or PS3/2 board and seeing if it is actually the motors?  FWIW, the PS/2 board or the PS3/2 board shouldn't have an issue with a couple of amps to the motors.

Yes.   I don't want to risk trashing a second board!   I'll make this thing as efficient as I can first!

Last edited by John Sethian

Mario

Thanks! I may call on you for these.

In the meantime I have established the board is OK, and that the GG1 won't pull squat with only one motor driving one truck, and the other truck totally free wheeling.   I have also established the Kohs pickups are quite a drag.  And they are on both sides.  Not a good design.  I partially addressed that, and improved the run time.

I am currently pursuing two options

1)  Go to more efficient motors (my original course).   My goal is to get below 1 Amp, where I know it will run for a long time.

2)  Put a second PS 3 board to drive the second motor and run the whole thing as a Lash Up. Per Pat's suggestion. Space is a challenge, but we'll see

Your fan gives me a third.

Incidentally, I considered dunking the board in a thick copper mini bath tube of fluorinert.

https://www.3m.com/3M/en_US/p/d/b40045180/

Would have solved the problem.  But sealing against leaks would have been a challenge.

John

I wouldn’t say a third option; more like a 1b and 2b.  Either way, they wouldn’t hurt. I’d say power them off a unused lighting feed off the PS3 board.  Cab light perhaps?

Well, if you could find one of the modified PS32 boards for one-gauge, those were beefed up with a heatsink on the motor driver FET, that would probably be one to try if you wanted to swap boards.

If you want to stick with the PS/2 board, adding a heatsink to the driver FET, even if you have to dispense with the plastic carrier, might be a smart move.  I'd also make sure the bridge rectifier has a GOOD heatsink, perhaps a custom one with a better bond to the chassis.  Those are the two high current critical components in the motor drive circuit.

Truthfully, I think just blowing air on it with a tiny fan is going to be a lot less effective than better heatsinking.  Adding the fan as well can't hurt...

Well, if you could find one of the modified PS32 boards for one-gauge, those were beefed up with a heatsink on the motor driver FET, that would probably be one to try if you wanted to swap boards.

Not a first choice, as I could not find one, AND I would have to change all the lights

If you want to stick with the PS/2 board, adding a heatsink to the driver FET,

Could I prevail upon you to show me where the driver FET is?

even if you have to dispense with the plastic carrier, might be a smart move.

I had actually considered that, but need to know where the critical components are to make sure I have decent high thermal conductivity path

I'd also make sure the bridge rectifier has a GOOD heatsink, perhaps a custom one with a better bond to the chassis.

Same request about the bridge rectifier

Those are the two high current critical components in the motor drive circuit.

Thanks in advance!

Truthfully, I think just blowing air on it with a tiny fan is going to be a lot less effective than better heatsinking.  Adding the fan as well can't hurt...

Last edited by John Sethian

Here's the motor driver FET.



A 1mm thick copper strip soldered along this edge and folded under the PCB (with some Kapton tape to insulate the board), would be good.

Can't miss the bridge, it's the big flat component that already has a heatsink.  My point is making that heatsink better as leakage through the bridge when it gets hot can compromise the motor driver FET.

Attachments

Images (3)
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You may be better off using thermal epoxy and gluing a large heatsink on the FET instead of trying to solder to the FET.  It's not as effective, but it's much easier to do without killing the board.

I’d check to see if it’s tab is soldered to the board, and if it is, see if they’re using thermal vias to get the heat to the bottom of the PCB. If it’s not soldered, then I’d try bending the legs up and get it to stand and then you could attach a larger heat sink to it. I wrote a paper based on lab work I did soldering these to heat sinks for Rockford Fosgate way back in 06, before they moved production out of Arizona. They were driving so much power through there that they used tin plated copper bus bars as heat sinks. I’ll see if I could dig up my presentation. As for the bridge, last build I did I mounted the board upside down and used thermal tape to use the frame as the heat sink. Good times.
- Mario

I’d check to see if it’s tab is soldered to the board, and if it is, see if they’re using thermal vias to get the heat to the bottom of the PCB. If it’s not soldered, then I’d try bending the legs up and get it to stand and then you could attach a larger heat sink to it.

It's clearly soldered to the board, it's a D-PAK surface mount part.  The only connection to the center pin is the pad.

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