Heng Long RX18 to a mato chassis PROBLEM

[AlwynTurner]

Hi can someone who has done this please advise whether/how I have cooked an rx18 board by connecting a mato chassis to it? I got a mato chassis from forgebear and proceeded to connect it up to a supposedly 'new' rx18 that I had bought and got a burning smell and smoke from the rx18. All I connected was the power, left and right motors, receiver board (brand new from forgebear), loudspeaker, and volume control. Switched it on to test and burning smell and no action. Helpplease, did I do something wrong or have I got a duff rx18 board to start with? Thanks Alwyn

[AlwynTurner]

Oh D*&n!!! I think I have just spotted the problem. The mato chassis has the positive wire from the battery going to the lower prong of the connector, whereas the RX18 wiring diagram and the new attached power cord provided with the RX18 have the positive going to the upper prong, so I suppose giving the board 7.2v with the wrong polarity would tend to fry the board!! Much profanity and annoyance. I am really really cross with myself for not checking, I would never have thought that the two tanks would have such fundamentally different connection strategies. Anyway mystery solved, just need a new RX18 which I will now order. Bl@st.

[hawkeye3guns]

Hi mate
I toasted 3 RX -18's on the same conversation And found the problems (apart from the polarity) was also the supression diodes on the drive motors Matro motors are supressed differant from HL and that caused me to burn out 3 RX-18, When I changed the suspression to match a HL gearboxes the problem was solved.
I put a post on this forum about it in the electronics section
regards Denzil

[AlwynTurner]

Hi Denzil, I have searched high and low in the electronics section, can you please point me to where in the electronics section it's posted - it's probably my eyes but I can't find it. Thanks Alwyn

[edpanzer]

viewforum.php?f=77
There you go Alwin

[AlwynTurner]

Hi All, I've had a pm from Denzil and it's on page 14 of general questions, just in case anyone else finds themselves converting a Mato chassis (or gearboxes) to an rx18 board - beware, those motors bite!