11 replies to this topic

[crazyphysicsteacher]

I have had my trusty DR30 with one of the original diode brake switches for about two years now. The controller had its issues but I fixed them all.

 

Today I ran into an issue, we run a 4.5 NASCAR with open S16D motors and now use 72 pitch gears because of mesh issues. Back to my question, while running today I lost sensitivity for the bottom half of the travel, made the car real hard to drive, I also seemed to lose brakes at the same time. During this time the car was a handful to drive and the controller got real hot. The same issue popped up in the next race but there we ran Sealed S16D motors with jk 21 chassis with jk Dyson bodies. The car was good but I lost brake and sensitivity during the race, not as bad as with the 4.5 chassis but enough to turn the car from a corner diver into a floater, I just managed third.

 

If anyone has any ideas, I am open. The board is clean and the contacts are clean and well taken care of. I have looked at the fuses and they are both fine. I wonder if one of the transistors is overheating? Nothing is burned or discolored.

 

Now I know I could just pack up the controller and send it to John, but I like to fix my stuff and I understand a bit more than the average bear.

 

Thanks in advance for any help.

[drrufo]

Did you just look at the fuses or did you take them out and use a meter to check for continuity? What values are the fuses?

 

It sounds ike you changed the way you use the controller. If you don't use full throttle, the controller may overheat because the transistors are putting out more heat. 

 

Are any of the wires broken? Do you get the sensitivity back after the race, after the controller cools?

 

If you continue to have the problem, contact me directly. 

[Ramcatlarry]

I had an issue with mine recently as well and discovered an arc pit had developer on both the contact screws and the plates. Cured it by cleaning and tinning the brass faces to reduce the corrosion.

[drrufo]

Larry,

 

That was caused by arcing between the saddle and the brass screw head. That is why I recommend that everyone burnish those after each race session. 400 grit sandpaper folded and pulled between the two sides will clean the arcing.

[crazyphysicsteacher]

John,

 

The controller returned to normal after it cooled off and you are correct, the car got tight and I could not open it up as mush as I wanted. But, the trouble with the controller only got worse as I fought the car and the controller.

 

I checked all the wires and the fuses and they are all good. The brake fuse and the power fuse are 10A and 20A from Radio Shack as the instructions called for.

 

If the controller acts up again, I will shoot you a message.

[drrufo]

I would look at the solder joints at the diode on the heatsink. The transistors may being going bad but I would need it here to determine that. Can you check the value of the sensitivity pot? It has the proper value on the back, the value is behind the "r" on the back.

 

With the sense pot and the brakes going away I would look at the heat sink.

[Tex]

I don't know beans about controllers except how to pull the trigger. But I experienced the exact same symptoms with my DiFalco some time ago... nothing would happen until the wiper button was about halfway across the bands. A knowledgable local pointed at a round silver doohickey on the heatsink (down near the alligator clips) and said the silver doohickey was probably bad.

 

I never found out if that was specifically the problem 'cause I wound up letting it sit for a year or more and then sent it in for a big refurb/upgrade.

[Bill from NH]

That round silver doohickey on the heatsink was probably a power transistor.

[JerseyJohn]

Sometimes shorted transistors appear to function normally but once the get hot things go sideways. All things being OK I would replace the transistor.

 

Also with the motors you're running the transistor would get warm but if it's almost too hot to touch adios that bad boy.

[drrufo]

Jersey John,

 

I have racers who complain about the heatsink getting too hot to touch. This is on DR30 controllers that work perfectly. The racers are not going to full throttle, but running in the top third of the wiper array. That gets the transistors hot and burns the resistor on the back of the board. I had that resistor melt while trying to find a low wiper band in the upper range. The coating on the resistor ran like warm icing on a cake.

 

I have increased the watt rating on the resistor but they still get warm if held in the upper range too long.

[crazyphysicsteacher]

John,

The solder joints are okay and show continuity at the joints. The pot shows 50 ohms, no decimal point. I am going to be back racing on Friday and will be able to check the controller out more then.  I also just found that the second car had brush springs that went flat and lost tension.

[crazyphysicsteacher]

I tested the controller night while racing 16D flexi Nascar and it was okay.  I did not notice a problem with sensitivity and I think all may be okay for now. 

Thank you all for your help and information.