Repairing Novak 4 esc _ what tools and what parts?

[JosephS]

You could also remove one of the other FETs and use it as a guide to trim the leads on the replacement. Make them a close match and put them back on the board to verify that the tops of the built in heatsinks are even.

The trick to soldering is to get the lead and the trace on the PCB ho enough to accept the sold. The solder should "flow" into the area around the lead on its own. If it drips in and forms a "ball", that means it wasn't hot enough to flow properly. Also, a good connection will be relatively shiny. If it looks gray and rough, it is a "cold" joint, which is another indication that the solder did not flow properly due to a lack of heat.

If you are near southern Indiana, swing by and I can help. I am not good at very many things, but I can solder pretty well thanks to my vocational school teacher and the US Air Force.

Thank you for the advice. Lucky for me the fets bottom sits flat to the board, so the heat sinks all line up.

I'll re-read your advice when I get a chance to put solder down. I'd take you up on the offer for help but I am about two thousand miles away. I have 2 more novak 4's that are in better condition. So I have plenty of chances to get solder it right

My iron has a temperature selector and a few different tips. Any clue on what temperature I should be using ? Is the fine tip a good choice?

[1911Colt]

Fine tip will work, but if you have a larger one, it will transfer the heat better. The smaller tips are good for tighter spaces and small and/or easily damaged components. The down side to small tips is that they don't retain heat well. Instead of quickly heating the PCB trace and component leads, the tip itself cools down. To compensate, you have to hold the iron to the lead a lot longer. The chance of getting a "cold" solder joint is higher with a smaller tip. If you are patient, and make sure the solder actually flows into place, it still works perfectly well. FETs are relatively large and durable compared to other electronic components, so they are not at risk when you use a larger tip. A tip about the size of the FET leads or even a little larger would be perfect. Anything can work, though, so don't sweat the choice of tip size too much.

The temperature is not 100% crucial, either. It is somewhat dependent on the solder you use. Without seeing the equipment and the solder, I would suggest starting at around 700 F. Before trying to solder the FETs, just hold the iron up and touch the solder to it. The solder should melt right away, within a second or two. If it takes 10 seconds, or even 5, turn up the heat 50 F and try again. Depending on the iron you use, it may heat up immediately, or it could take 20-30 seconds. You want to make sure the iron has reached full temperature before doing the test. Many soldering irons have a light that flashes during the warm up period and goes solid when it reaches the set temperature, so that helps. Or just be patient. Turn the iron on and and do something else for a few minutes. Note, too, that this flashing light is helpful if you use a smaller tip. If the tip does cool down temporarily, you will know by the light starting to flash again. You will know to a) use a larger tip or b) be patient and give it time to heat up until the solder flows properly.

It is not uncommon to end up soldering at 900+ F, but if you aren't familiar with the process, your equipment, and the solder, it is better to start lower and work up to the right temperature. Also, the temperature settings on most soldering equipment are just "ballpark" figures anyway. They aren't very accurate (unless you have professional gear). So the temperature setting is just a guide. The truth is in how the solder flows.

[jwscab]

I haven't popped into this thread for quite a while. Sounds like you're handling things just fine. In general, devices in that package don't sit flush to the PCB, that is a unique construction for our hobby to make the footprint small and help ruggedize the assembly. So that wider lead makes sense, it's usually not a critical dimension. When you solder, use leaded solder it will flow at a lower temp and just better in general. Make sure you add a nice even amount along the leads, usually you leave the lead lengths kinda long to add more current capacity as they lay over and overlap, but what you have is fine.

One last word, on FETs in general, they are very very static and voltage sensitive so always use caution with them when they are not in circuit.

[JosephS]

I haven't popped into this thread for quite a while. Sounds like you're handling things just fine. In general, devices in that package don't sit flush to the PCB, that is a unique construction for our hobby to make the footprint small and help ruggedize the assembly. So that wider lead makes sense, it's usually not a critical dimension. When you solder, use leaded solder it will flow at a lower temp and just better in general. Make sure you add a nice even amount along the leads, usually you leave the lead lengths kinda long to add more current capacity as they lay over and overlap, but what you have is fine.

One last word, on FETs in general, they are very very static and voltage sensitive so always use caution with them when they are not in circuit.

I have some silver solder, would that be an ok substitute for lead? Other that than I only have lead free solder.
Now that I think about it I have have a roll of very old radioshack 60/40 somewhere, though it is thin.

Would damage to them show up by using a diode tester? The Fets were shipping in a regular plastic bag in a bubble mailer?

[Frankentruck]

It seems like silver solder usually has a much higher melting temp snd doesn't fliw as well. I personally wouldn't use it for this. I'd use silver solder only for attaching wires to motor terminals, if I was going to use it.

[jwscab]

Usually a diode tester will be low enough voltage not to damage FET's. The tube they shipped in is esd proof, there might be a little lightning bolt symbol on it if you look carefully.

Silver solder will probably work fine if it looks like regular solder it's probably very low percentage. High percentage stuff is pretty stiff. But the silver adds great conductivity. It usually is a bit higher in temp.

[JosephS]

Usually a diode tester will be low enough voltage not to damage FET's. The tube they shipped in is esd proof, there might be a little lightning bolt symbol on it if you look carefully.

Silver solder will probably work fine if it looks like regular solder it's probably very low percentage. High percentage stuff is pretty stiff. But the silver adds great conductivity. It usually is a bit higher in temp.

This was a amazon special order, no anti-static tube.

[JosephS]

That didn’t work.

There is a short… somewhere. The bec is working and powering a receiver. But my power supply is pulling 3 amps. The motor is getting 0 amps or voltage.

I think I am going to pull all the parts off and try again.

If I am thinking about this correctly. I can pull all of the fets off the board and then check to see if there is still a short.

I should be able to add one fet at a time if everything is in working order.

Once the parts are all tacked down I can add more solder to the joints.

[jwscab]

If you have the brake fet installed, I would try removing that guy first.

[JosephS]

If you have the brake fet installed, I would try removing that guy first.

Thanks for the tip. Looks like that wasn't it.
I just noted that the high current draw doesn't happen until the blue motor lead is connected to the motor.

[JosephS]

https://www.finepowertools.com/diy/soldering-defects/
https://www.seeedstudio.com/blog/2021/06/18/13-common-pcb-soldering-problems-to-avoid/
https://nancylthamilton.com/techniques/soldering/soldering-101/
https://www.wikihow.com/Practice-Soldering