NitroAssassin

Just curious how many of you have blown your rx13 & rx14 boards and what do you think caused it?


After seeing how heavy these tanks become with the metal running gear (wheels and tracks) it's safe to say the main reason for blowing the FETS is obviously the current draw is exceeding the threshold of the FET/ circuitry..

Last night my friends tank blew an rx14 board... Why I don't know, not sure if it's something he did before I got there or what.. anyways thanks to TJM who had some boards IN STOCK lol we got it back running last night.. This time I soldered some a blade style fuse block inline each power wire going to each motor from the board.. I started off safe with a 2 amp fuse, we drove it around for awhile without any troubles...
Then i wanted to see how much it would take for the fuse to blow so we started putting the tank through more challenging stuff.. We were climbing over shoes when the left track got hung up on one of the shoes.. We rocked it back and forth to free it up, after a couple attempts the left side cut out.. I took it apart to check out the situation and sure enough the fuse gave out.. Swapped in another 2 amp fuse and we were back to the races.. We didn't have a 3 amp so i couldn't test that but I assume a 3 amp fuse would work fine and be a safe threshold for the board.. Without the metal running gear the motors would obviously be laboring way less so there would be less current draw from the motors.

Here's a pic of how I wired up the inline fuse blocks.. I didn't use the full size fuses you find in cars, i used the mini style blade fuse..



It's a very simple idea and some of you have probably already done this but for those who haven't, it might save you some aggrivation on that sat or sunday afternoon when you're out battling your buddies and a board goes on you..

[8D]

madbadger

if you don't use the smoker, remove it, place it in the nearest bin. Now mount the RX14 board (with plastic motherboard posts) where the smoker used to be face up. Get some ****M memory heat sinks (from Maplins or a good electronics shop) and fix them either side of the mosfets. Then get a Socket 7 cpu fan (it doesnt matter about it being 12volt) and mount it behind the RX board on the back of the battery box using two of the holes in the fan. The fan should blow over the heat sinks that are stuck to the mosfets. I have this setup and ive run my Tiger 1 for 3 hours solid using a 4600 battery and pushed it quite hard. It seem to be ok, and its still going strong, in fact i have converted my Tamiya King Tiger to HL electronics with the same fan setup.

ps wire the fan to the smoker output, but don't forget to switch it on. the fan will start running once the tank is running (when head light stops flashing)

hope this helps

Kev

NitroAssassin

madbadger, I thought of doing a similar idea to what you said, i have all those parts laying around here from my computer tech/system analyst days. I have the fan wired directly to the switch so as soon as you turn it on the fan starts.. We'll see how it works in my friends tank with the rx13 board that's pictured above.. As for my first Tiger with the RX14, i'll probably end up doing what you did to yours..

NitroAssassin

out of 65 views nobody else has blown boards ? maybe nobody wants to admit it

shenlonco

My Feedback: (2)

Actually that's a great idea...they started using something like this on the Blade helies because if you crashed and left the throttle on it would blow the board out.... Don't know if there fuses ...But i do know they sell heat activated switch type things thermal protectors i believe... they open up at a certain temprature and act like a fuse but when they cool down they connect the power on again....may want to look into these this way you never have to open the tanks for a blown fuse.

shenlonco

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Like these!


http://cgi.ebay.com/Uchihashi-Therma...3286.m20.l1116

NitroAssassin

that sounds like a neat idea schenlono..

After I installed those fuses I immediately thought of a better to make them more accessible incase you needed to change one without removing the upper hull.. If you would get the twist in style fuse blocks that accept the small glass type fuses you could drill a couple holes in the bottom of the chassis and mount them underneath.. You would be able to just twist the fuse holder cap off and replace the fuse within seconds without taking it apart..they're low profile too so you wouldn't have these 2 protruding things sticking out from underneath the tank that would cause you to hung up easy on obstacles.

just an idea[8D]

shenlonco

My Feedback: (2)

Yea i think i would rather use something like above... but it will probably be trial and error you may need more than the 2.5 amp one who knows!

YHR

I blew 3 boards on Saturday alone. THought it was my wiring the cannon flash LED. Turned out I had one of the drive motors shorting out across the gear tower frame, only when the top half of the tank was on. Just the chassis running around was fine.. I am listening to the ideas proposed here. I like the thermal fuse the best. Do they make 2-5 to 3 amp thermal fuses??? I didn't check the ebay link, but if they do I am in

NitroAssassin

the 2 amp fuse I tried was basically just a test since I knew it would blow fairly easy, 2amps isn't much at all for an electric motor of that size to draw under load.. I'm not sure what the limit on these boards are yet but I would bet a 4 amp fuse would be the highest. Just driving around on smooth surfaces or outside in the driveway the 2 amp would be fine.. For grass I would say 3-4amp for sure. The major spike in amperage draw is obviously when the tracks get hung up and the operator tries to muscle the tank through, this is where the electronics take it.. I can't see them making a circuit for these tanks that would burn out with a 4-5 amp draw.. I do have an amp meter that registers amperage draw, it would be good to see what the limit is.. To test this would be to sacrifice another board.. []

NitroAssassin

YHR, you blew a board from the motor shorting out against the gear tower frame? can you explain a bit more how that happened? I'm trying to picture what you said but i'm having a hard time, maybe it's the way you worded it.. I can't see how the motor can short against the gear frame when it's directly mounted to it.. I can see your motors shorting out against themselves since they are close together..

I was actually commenting about the motors being a possible risk for shorting the other night when i was soldering in the fuse blocks..


I think It might be time to come up with a circle check list for all the HL tank owners.. All the strange things that we figure out with these tanks through trial and error or experiments should be put into a txt file.

shenlonco

My Feedback: (2)

Hi do a search for thermal cutoff with the amprage you are looking for in front Like this ( 3A thermal cutoff ) try e-bay then the web search...you should find them they come in all sizes...

shenlonco

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YHR here are the 5 amp ones the e-bay seller also has 2.5 amp ones i think so you may want to try them both out.

http://cgi.ebay.com/MD-142-C-142-DEG...3286.m20.l1116

YHR

The gear towers in the Sherman are so close together that the contact on one motor shorted out against the frame of the other tower. I had been banging it around in the snow in the back yard and I must have flexed the chassis enough for the short to occur. I have since insulated them against this ever happening again.

Thanks Shenlonco for finding what we need. Simpliest solution to prevent smoking boards.

shenlonco

My Feedback: (2)

Cool let us know how it goes.

ManMachine

I have nothing to hide, I have managed to blow 4x rx13 cards

Gabriel

sjgusmc21

Amazing. Never new these existed. Will definately install them. Thank again for the suggestion!

darkith

Also know as a PTC or resettable fuse. Somebody posted a mod where they added them onto the RX1? board a while back.

D.

madbadger

Nitroassasin

i can see where your friend has put the fan above the RX13 board in the photo, i to did this, complete waste of time, it only blows air onto the bottom of the board and not onto the transistors/heat sink that is fitted to the RX13 board. Best thing to do, is fit a RX14 board like i explained. Where the board is fitted upside down in the base of the tank, there isnt enough room for a constant air flow around the chips/transistors heat sink. I fried 2 RX13 boards like this and i even fitted a lump of alloy that sat below the board and superglued to the RX13 tin heat sink, as a remedy to increase surface area trying to drag heat away from the board.

where it is now, there is plenty of air flow, just junk your smoker, they don't last long anyway. Even the new RX18 boards need cooling, if i upgrade to a RX18 board for any reason, i will remove if from its plastic case and mount it under a fan.

Kev

NitroAssassin

madbadger, you're right about the fan being a waste of time on that side of the board.. I made him aware of that after I had seen what he did.. We originally had an rx14 board in it but one of the transistors blew so we put in an rx13 since that's all our local parts guy had lol its working fine so far.. The smokers on our tanks are already gone by the way..

How many rx13 boards have you burnt out and what were you doing when they went? I can't see the boards going just by driving the tanks around normally, i haven't blown one of my own yet but I haven't driven on grass or in snow.. It's mainly in the garage where we''re battling right now or just in the house.. I think the main reason people are burning these boards out is because they don't know when to let off the throttle stick when the tank becomes hung up or is laboring trying to climb something.
Sure there are boards that blew from being defective but most of it has to be user error..

Dmon1996

I've blown two Rx13 boards.

madbadger

one board blew turning round on soil, it didn't get stuck, just turning round.....the other climbing up a little kerb (about 2 inches high) which id climbed up loads of times, that time was a real smoker, there was smoke pouring out of the rear engine vents, i walked up to it and open the front drivers hatches and smoke pouring out of there as well. But on strip down could i hell as find the burnt components......very strange and no it wasn't the smoker as it was disconnected. I must tell you, the 3rd RX13 board i used (then swapped to a RX14) which i still have, i turned it up so the tin heat sink was on top, and it does get hot......i drilled small holes in it to try to disperse heat, but read on here that the 14 boards were better, i just ordered 2 and stuck it in straight away, fingers crossed, its still ok and so is the King Tiger i converted with the same gear.

hope this helps

Kev

NitroAssassin

interesting... well i'll have to see which one of my tigers die first lol one had the rx14 and the other has the rx13..