another tank problem!!

[betty.k]

you guys must be sick of me now, but anyway! everything s running fine except the left channel. when i push reverse, no prob s. but forwards it only spins at half pace. there s no stuttering, just acts like there s less voltage. it s not the tx, and when i do push forward, one or two of the transistors for that channel get really hot. so what have i done? the only thing i did differently was run it with the tamiya motors for a little while instead of the motors that came with the pcb. the tamiya motors spin faster and the stock motors have more torque. if i have to replace a component, some tips on working with teeny tiny components would be apreciated
obviously i m a bit bummed off about it, but i realise that problems like this (and you guys!) only serve to further our education in the rc world! ok, go forth and ponder!:8ball:

[micro_Amps]

You have frie one of the surface mount transistors. You might hae trouble ordering repalcements too. It sounde like the Tamiya motors drew too much current and fried one of the transistors in the “left forward circuit”
Hmmm, now its going to get complicated for you.
You need to identify the blown transistor, remove it and replce it, after first identifying what type it is and making sure you can get an equivilent replacement.
Godluck.
uA

[betty.k]

i,ve got a couple of spare blown pcb’s i’ll experiment with. in the mean time i just bought another one (they’re only $15!), whacked it in, and no prob’s!:D
i’ve worked out what to do now, make sure there’s a capacitor across the motor terminals and wire from one terminal to the motor shell, no more than 6V, and DON’T use the tamiya motors that come with the gearbox! every time i fried a pcb it was with those motors attached!:angry::8ball:

Edited by – betty.k on 14 November 2003 22:28:27

[micro_Amps]

You mst have a fair amount of spare parts building up by now.
:)uA

[betty.k]

ha ha 😀 you’re not wrong there! 2 x 27mhz tx, 3 x 40mhz tx, 2 x mostly fried pcb’s, 1 mostly working, 1 still in box, 8 x motors, and heaps of gears and wheels and switches and wires!! still worth every cent though, cheap education. tx anyone!?:8ball:

[micro_Amps]

Just wondering, do they have a ‘PT’ writen on the main chip in the Tx and the Rx. If so what are the numbers following the PT on the Tx and the Rx?
:)uA

[trash]

I haven’t looked at the specs for the 8050’s that uA has in his cct diagram, but you might like to compare them to BC848’s and BC858’s. These are the SMD versions of BC548,BC558.
They’re general purpose transistors and you can do lots of different things with them and not have to worry too much about the finer points.
Perfect for blowing up and they’re much cheaper than $15 each. 🙂

Since your 8050’s etc are just running in saturation and you’re keen to blow anything up. You might like to try replace the SMD’s with the TO92 style (normal) transistors. If they work, then try the SMD. Given that you don’t seem to worried about size, you might just care to build external drive transistors for the bigger motors.

[micro_Amps]

Or go with low resistance (high current) fets instead of the transistors.

:)uA

[betty.k]

i was waiting for the ‘f’ word to surface from uA!!:D

the tx chip has a logo that says ‘actions’ or ‘ctions’. there’s two sets of numbers; ‘tx2c’ then ‘bb024-18’. the rx has the same logo, with the numbers; ‘rx2c’ and ‘bc017-18’. the rx chip has 16 pins and the tx has 14.
thanks for the info, and whadda ya mean i’m keen to blow things up?! aren’t we all! i’d really rather not toast pcb’s, but there’s a helluva steep learning curve when you do!:p:8ball:

[trash]

I blow stuff up all the time, sometimes deliberately sometimes not.
I meant to mention a few good things for working with SMD components. The first is a matchstick.
Lick the end (not the head end stupid !) and touch the SMD component. It picks it up and you can place it on the board to be soldered holding it down and in place with the matchstick.
Next is a fine point tweezers for picking of components. And of course a nice fine tip soldering iron.

uA likes to be a bit more specific than I do.
Ask him what the T stands for in FET ?
I’m willing to be it’s not going to be “thermonic” or “tube”.
blackeye:

[betty.k]

nice touch with the matchstick. it’s the same principal behind picking up a blob of cigarette ash, by licking a finger and gently touching it to the ash!
what does smd stand for? i know the technical term is ‘itty bitty teeny weeny electronic thingies’!
and while we’re at it, what’s the ‘t’ mean? and all the other letters? and, (i’m on a roll here!) what does ‘lol’ mean? and what’s so special about a ‘grandcell’ charger? and… ahh bugger it, that’s enough. i’m starting to annoy myself!:8ball:

[trash]

S urface
M ounted
D evice

F eild
E ffect
T ransistor

Fet’s are a bit different from common ‘bipolar’ transistors. I have no idea why they are called bipolar ?

I don’t know what’s inside a grandcell charger,
I’d guess it’s some sort of pulse charger.

I just blow cigarette ash away ? 😯

The common biro pen requires gravity to work.
The Americans spent thousands of dollars developing a pen that would work in space.
The Russians used a pencil !

I might add that the space shuttle never had graphite fragments get into it’s circuit boards.

[betty.k]

actually ordinary ballpoint pens do work in space! (new scientist, 1 nov 2003) a spanish astronaut on a recent shuttle flight who usually used the fancy pressurised nasa pen, noticed a russian crew member attach a regular ballpoint to a piece of string before liftoff. turns out they allways used ballpoints, everyone just assumed they used pencils!:p:8ball:

[trash]

Wow. looks like I’m going to get this months NS,
I only get it when they have a catchy cover story.

I wonder how long normal biro’s work or why they work in space. Writting upside down here on earth they don’t last long.

[betty.k]

ahh, if you write upside down gravity pulls the ink away from the ball, and alllowing air in. in space there’s no pull any way, and capillary action probably takes place to hold the ink to the ball……i think:8ball:

[micro_Amps]

Quote:

I have no idea why they are called bipolar ?

Is it because they have unexplained mood swings?

A transistor is either PNP or NPN (pos-neg-pos or neg-pos-neg)
These 2 sets of ‘pole junctions’ is where the bipolar name comes from.
Standard transistors, as above, are also BJTs, or Bi Junction Transistors, for obvious reasons.

Betty.K if you are using a RXc2/TXc2 chipset thenn you have the option of using a turbo function as well, same as the booster cars, with normal speed on 1/2 and turbo on full speed. If all the pins on both chips are exposed that is.

:)uA

[betty.k]

sounds a little complicated to me. but if it’s simple, let me know:8ball:

[ph2t]

betty, I would go the full monty and get some mosfets to power that bugger. Don’t just limit yourself to the standard ones made popular by the german’s fet mod. Use some more powerfull ones. As long as they have the propper “turn on” voltage you will be sweet. You could then run the motor circuit off a higher voltage and really toast those tamyia motors, yeah!

As to replacement transistors on the PCB, just pull the spare ones of another pcb, or order some as free samples from http://www.onsemi.com. You could try the MMBT2222 as a replacement for the NPN ones and the MMBT3906 for the PNP. These are surface mount versions of some standard and popular small signal switching transistors…

ph2t.

[betty.k]

no worries. i’d better stop asking questions now, this and trash’s tutorials will keep me busy for a little while!:dead::8ball:

[Pork_Hunt]

I’d go with relays myself, only coz I am comfortable with them 😀

ph2t (how do you say it, “fatootie”?) I bought a microsub from Jaycar that is a rx2/tx2 chip and it has “tank style” steering and a turbo and I was wondering how the hell it is wired up

Edited by – Pork_Hunt on 21 November 2003 03:38:21

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