Rumba Board Problems

Rumba Board Problems

RUMBA BOARD PROBLEMS

Only three days into printing on our new machine and the skeletons decide to come out of the closet. Problems I hear you say, yes problems with a capital ‘R’. Rumba Board problems to be exact.

Before purchasing a part you usually have in your mind a list of requirements that the item must be capable of producing. For us we wanted a multi operating voltage control board as we wanted to run 24V on the hotbed and nozzle to reduce heat up times when printing ABS. The Rumba Board specification states 12Volts to 35Volts so that ticks those boxes . With all our other boxes also being ticked by the Rumba board we made the decision to use it. Next you start to look at the reviews of people who have already purchased the board and yes all seems positive, in fact loads of positive reviews and even the sellers recommend the board as well but they would……..wouldn’t they?

So what went wrong?

In reality all is not what they state on the can. The bells should have started to ring when we tried to connect the LCD display screen to the board. There are two plugs named EXP1 and EXP2 and obviously you would of thought they connect to EXP1 and EXP2 on the display. Not on a Rumba they don’t. Somehow during the initial circuit board design they got the plugs wired the wrong way around so the Rumba EXP1 plugs into display EXP2 and Rumba EXP2 plugs into the display EXP1. To compound these matters the EXP1 plug has also been wired 180 degrees the wrong way so you also have to trim the plug so you can invert it one hundred and eighty degrees and plug it in upside down!

So what other Rumba problems are there?

The original Rumba board claims it can work with a power supply range from 12 Volts to 35 Volts. This is not correct due to the board is fitted with a re-settable fuse that is only rated to a maximum of 16 Volts. Therefore using anything over 16 Volts could mean you will end up with a board that would turn a steak medium rare! We have included a picture of our re-settable fuse after just 10 hours of printing. Luckily we spotted the problem before it got too serious. It is at this point when you start Goggling Rumba problems and you find out more than you have initially bargained for. We found that the way people get around the underrated fuse problem is to fit two car blade fuses to the board so we upgraded our board by carrying out the same procedure. A link on how to carry out this modification is at the bottom of this page.

With that upgrade done can we now please continue?

Well only for Fifteen more hours of printing because then we hit another problem. The hotbed has lost all power.

On investigation we find the Pcb solder routing to the hotbed MOSFET has blown. It is again time for Google to explain and it does not take long to find out the MOSFET’s fitted to the board do not like to be used as they are not up to the task. This is because they are not true “logic level MOSFET’s”. To me and you this means that they are a cheaper option that does not switch completely ‘On’ when operating with a 5 Volt controller. The lower voltage control signals cause inefficient operation and significant self-heating. On top of this the designers have forgot to fit suppressor diodes to protect the MOSFETs from any sudden voltage spikes that can occur during switching loads for example switching on and off a hotbed heater element. Here is a picture of what a voltage spike thought of our board.

There is a now a new and improved version of the Rumba control card online that claims to have sorted out all these problems. It is called the Rumba Plus and there is a link at the bottom of the page. The problem with this board is availability because they are no longer available from the board’s manufacturer. But there seems to be a lot of copies of the new board floating around on the web claiming to be a Rumba Plus. These copies do have upgraded fuses fitted but there is no mention of any improvements being made to the MOSFETs and the addition of suppressor diodes.

With this level of reliability would we buy another Rumba control board? No

As our board is now a crisp did we buy another? Yes

Explain yourselves I hear you ask. Well is it stubbornness or stupidity? To be honest a bit of both really. We still want the six drivers this board offers and we have designed and printed a lovely box for it. Though most importantly we also have a new plan. The board must be capable of operating with 12 Volts (unless you know different) because of all the happy punters who purchased and now use one. Our new plan is to run two separate power supplies on the new printer. One 12 Volt power supply feeding the board only, which should please the Rumba board. An additional independent 24 Volt power supply will be used to power the hotbed and nozzle through external superior MOSFET units whose operation will be controlled by a signal from the Rumba.

Simples!

Some useful links with reference to this blog

Upgrading Rumba Board Fuse Procedure

Rumba Plus

Rumba Plus GitHub Files

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