When you fry a board, what exactly do you fry?

[viperdout]

Well, for all the people who think 6 volts is safe, it is not. Well, I hit the foward button on my controller for a second, and it stayed on and started smoking! I thought about it, and I coulda' used it for a ZZ. Anyway, what fries.

BTW: I had the first gen DKS 3.4, (mind you, the car ran for about 30 seconds before I turned off the hyper charger ) on it. I thought I had finally fried it (it's been 4 years), popped it into a stock ZZ, and it runs fine, though it's a little faster in reverse than forwards, but hey, all the others on 6 volts have died!

[Racer9]

It will fry the transistors and the chip the easiest.

[viperdout]

You mean the junk under the black stuff? I think it's also the transistors, because it's getting constant, but only partial power. But there is some melted solder under the black stuff.

[crazydave]

The junk under the black epoxy blob is an IC. "Integrated Circuit". It's the brains of the car. The transistors switch the power on and off.

One time I fried a steering transistor when a steering wire shorted on my tri-cell pack. The thing exploded, and popped off the board, blackening everything around it, and melted the isulation on the battery, but I've since replaced that transistor, and the board works fine.

My current car is running 5.5+v, and I've had no ill effects.

It's probably not the safest idea to run 6v, but it has been done, so I really believe something else happened. The constant, but partial power, really sounds like a short to me..

[viperdout]

Cool! Dave, I thought that the SE batts were 2.4 volts each. Are they cranking out more than what they are rated for? Also, I have so layman's button cells lying around crying out for some action...

[boho]

It could also be a partial open. I recently fried a couple transistors because one of the connection pieces for the motor was not completely touching the motor. As soon as I reset the motor it worked fine. So, if you replace the contacts, with say wire or something, make sure you've got good contact. The symptoms usually include a lagging motor and the pcb getting hot over the transistors or the brain.

[crazydave]

Originally posted by viperdout
Cool! Dave, I thought that the SE batts were 2.4 volts each. Are they cranking out more than what they are rated for? Also, I have so layman's button cells lying around crying out for some action...

The 2.4v rating is an average voltage. They will have more than that when full, and less than that when drained, and they should stabilize to somewhere around there after sitting.

When I pull mine fresh off the charger, it's reading 5.63v, so despite the batteries rating, that is how much is actually hitting the PCB.

[ph2t]

crazydave, a few notes dude.

The voltage you read, was it without the batteries in circuit? ie: not connected to the pcb? If so then this voltage isn't a true representation of what the batts are putting out. What I mean is that the multimeter you are using has a real high input impedance (high resistance) so when it measures a voltage it's not putting any load on the circuit in test. I suggest you put a 200 - 500ohm resistor across the batteries THEN test the voltage whilst this resistor is connected, this will give you a more accurate reading on the actual voltage.....

Does this make sense? I sounds a bit tricky I know...

Also the max theoretical voltage the PCB can take is 8V. This is the limit of the input voltage on the DCDC converter (the 3 pin black chip near the orange looking glass cased diode). The DCDC converter will take an input voltage of 1.2V(min) and convert it to 3V to run the RX chip AND the RF receiver circuitry.... If you put 3V, 4V or even 5V into the pcb, it will still supply the RX chip and RF receiver with 3V.

Many people fry their PCB's due to the extra voltage going through the h-bridge transistors (the part that drive the motor fwd and rev). If you put fets (singe, double or even triple) you negate this issues cause the fets can handle a hell of a lot more current than there stock BJT counterparts.....

catch my drift..?

cheers,

ph2t.

[viperdout]

Originally posted by crazydave
The 2.4v rating is an average voltage. They will have more than that when full, and less than that when drained, and they should stabilize to somewhere around there after sitting.

When I pull mine fresh off the charger, it's reading 5.63v, so despite the batteries rating, that is how much is actually hitting the PCB.

So does that mean my Laymans cells will be higher than 4.8 when I charge them?

[crazydave]

Originally posted by viperdout
So does that mean my Laymans cells will be higher than 4.8 when I charge them?

I honestly don't know. You'd have to check for yourself. All batteries are different.

...but ph2t just reminded me of a good point, I need to check the batteries under a load, to see what they're actually hitting the PCB with.