Roomba Scheduler Short Circuit

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Roomba Scheduler Short Circuit

Postby sundewzer » October 27th, 2015, 11:51 pm

I just got an older roomba scheduler model 4233. It didn't come with a battery but I connected one from an old cordless drill with a cell or two removed. I was very happy to get lights and movement but shortly after I did I managed to short out the power leads. One of the clips slip and turned in to a jumper from the positive and negative. There was a good spark and now I get no lights or movement :cry: I guess the first question I have is there a fuse of any sort that I might have blow or can I just count on the board being scrap?

Last edited by sundewzer on November 5th, 2015, 8:47 pm, edited 1 time in total.
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Re: Roomba Scheduler Short Circuit

Postby mfortuna » October 28th, 2015, 6:12 am

Search RR for schematics and you will find one labeled charging control. That gives you the path for the battery in. You may have gotten lucky and only damaged one or two components.
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Re: Roomba Scheduler Short Circuit

Postby sundewzer » November 7th, 2015, 7:44 pm

Thank you very much for you help. I took your advice and found several componet that I smoked. I guess easy come easy go. I circled all that I found bad in red and good in green. I didn't take the time to pull the capaciotrs out of the circuit to test them. It also seem like there is a good chance I burnt up U3.
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Re: Roomba Scheduler Short Circuit

Postby Gordon » November 8th, 2015, 3:19 am

sundewzer wrote:... I guess easy come easy go...
And it takes only a few seconds.
Unfortunately, you are just getting started! There are almost a dozen additional schematics that you must study and examine their related components. The one you found is "schematic1". Search also for: schematic2, schematic3, schematic4, ...schematicN, in which 1 =< N =< 12. Schematic12 was not entirely drawn, many pages would be required to show it all, but fractional parts did get posted.

When dealing with this reverse-current scenario it is very important to recognize that all five motor drivers, and the speaker too, have their driver xstrs protected by diode pairs connected from VBATT-to-xstr_base-to-SYSRTN, and ordinarily handle fly-back voltage generated when a motor is shut off. All those diodes become FWD biased under the reverse-current situation. Many become over stressed by the heavy surge current; and, that heavy current is collected and passed through the master, system-current shunt resistance provided by R148//R184 (which can be seen in schematic1, Zone-A3). Those resistors probably no longer have their original low value of resistance.

Generally, an owner is much better off to simply buy a replacement mobo, rather than go through the agony of repairing / verifying all sub-circuits!
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