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Testing speed controls

2297 Views 21 Replies 14 Participants Last post by  Krisfo
I have 2 Quantum speed controls one stutters under hard acceleration (just out of a corner) and the other just doesn't have the zip it had last year. The car doesn't have the speed it had last spring. The batteries are new and test fine the motors have been equal to what was in the car last year. Could an ESC still operate but have power loss? It acts like a V-8 with 2 cylinders missing. I have both set for max punch and they have been reset several times to make sure it was getting the proper trigger throw. Nothing else has changed.
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I have seen bad fets in the middle of the curve and you can test the sepeedo with a volt meter.....Test the voltage in the batt and then full throttle to the motor and test the voltage at the motor...SRM
It can be the ESC, but it can also be the track's condition. It changes daily and maybe that's what's making your ESC control differently? Has the track had any drastic changes or laps faster or slower?

Justin #29
The track hasn't changed. The guy that missed the corner slams the outside wall launches past me down the straitaway! I'm about 3 laps off of a normal run. It acts like I'm over geared but its not. I'll use the volt meter to test it.
both my gm speedos did this.. i also had a cyclone do it to.. the cyclone got switched to the offroad profile,...changed it back and was fine... the others just loss power.. could have lost a fet.... i have noticed with lrp's after a hard hit they either work like crap or burn up... i wont buy another lrp... had 3 go bad... and at 150+ it aint worth it..
After alot of use most speedo's lose some performance over time.
I heard somewhere that you can send it back to LRP and they will replace it.
Not sure how much it costs though.
Ken,you also may be having radio problems.I and others over time that i have seen have trouble with the throttle pots going out.Car still runs,but like yours about 2/10ths off.If your speedos check out this may be worth considering.
I was thinking the same way about the throttle trigger on the radio.

I did check the radio. Actually, the radio I used was brand new. I even switched to my older one which I bought 6 months ago and the problem with speed was still there.
I've had 2 LRP's and both ran just fine for awhile, then just like you've stated, they ran flat. Junk them!!!
I just wish there was an easy way to tell if the fets were going bad or a way to test them. You spend all that time setting up the chassis getting the right gear and selecting the best battery and motor for the A-main then the speedo just fails. It would be a lot easier if they just stopped working. This is my 3rd LRP Qauntum since March. I quit racing electric to race Nitro in April and just started back up indoors and already out 3 ecs's. We wil see how Novak's new one performs.
Do you run the shottky diode on the motor? I had a Quantum last year and without the diode it seemed to stumble a little coming off of the corner. I put the diode on and this went away.
Send it back, I burnedup two q's a Q1 and a Q2, sent them back and had 2 brand new speedo's in 14 days. No charge.
JPH Racer,
Do you have an address or someone to contact at LRP or phone number perhaps?
Has anyne tried the GM SX12? It is a cool little speedo except for the fact the instructions make no sense, and you need a gm charger to really play with the settings.
Talk to Zubie I know he dabbles with the GM's.
I always run the diode. Where do you send them too? One should still be under warranty the other is over 6 months old. I can't LRP's site.
Stay away from the new GM,s. I bought two of them and both kept shutting on and off. I later found out that about 12 other guys in my area had the same problem. The v-12's were awesome but the SX series.........
The quantums are the best IMHO. Reliable, easy to set up, and good service.
mayhem:did you ever figure out what was causing the gm's to do that because i have one just sitting here and it seems a shame we cant trust them after paying as much as we do for these. if anyone can tell us how to fix the problem with these it would be greatly appreciated.p.s. ive sent more than 1 back and still the same thing.
I never did figure out what the problem was. One guy in our area could use them with no problems. He bought mine, ( I raced with him and he knew of my problems with it),and have raced with him many times since. He never complained and seemed to know how to get them to work. He just said they seemed to work in his car. I know he did use a reciever pack and i did not. Try that if you havn't already. The quantums work first time every time with no fuss. I'll never buy anything else.
i've never had a problem with my v12xcs, and i have 3 of them. the instructions warn to ALWAYS take the negative wire off the battery first, or the ecs can be hurt. i wonder how many have been damaged because of this??
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