tech advised better supply for mojo usb charging

My chord mojo went up in a puff of smoke and after repairing it the shop told me I need to use a better quality "outboard" supply.

I dont want to buy an overpriced version of the same supply that cooked the device on the first place (cheap phone charger) so I was hoping someone here could help me understand what it is I need so I can charge this thing safely. I'm guessing i should be looking for a regulated supply with sufficient current but that is a guess.

Apparently, for anyone who might be concerned about this, its the older mojos that are susceptible to this.
 

MAAC0

Member
2010-05-02 10:00 pm
Can You tell us what burnt in the Mojo ?
you can try a better 2 or 3A USB supply, which is standard nowadays for fast charging phones. But get a reputable brand one.
I believe a simple supply with a small trafo , bridge, cap and a 7805 or an LM317 regulator will do the job, but You can get some hum perhaps. It's a matter of trying.
 
I dont know what burnt. The tech doesn't work in the shop so I couldn't talk to them directly.

Guy in the shop said he has a charger for $400 but figured, correctly, that I wasn't interested in something that expensive. From that info I gather that there are more sophisticated units then those provided with phones. I think I was using a charger supplied with a phone when it went down.
 
The Mojo doesn't draw more than 1A, that's all the capacity you need (I've actually measured mine, and even from dead flat , 850-900mA is the peak draw even off higher-capacity chargers). Simply buy a reputable USB supply - Anker do some excellent & very good value units. Mine has run 3yrs+ happily charging off a spare iPhone charger. This is not difficult -

- and the idea of a $400 charger for a device expressly-designed to be charged from USB is ludicrous, to the point of repugnant.
 
I dont know what burnt. The tech doesn't work in the shop so I couldn't talk to them directly.

Guy in the shop said he has a charger for $400 but figured, correctly, that I wasn't interested in something that expensive. From that info I gather that there are more sophisticated units then those provided with phones. I think I was using a charger supplied with a phone when it went down.

Without knowing what blew up and why, your a bit in the dark.
Could be the charger you used was to beefy (too high voltage) for it.
You need to get the correct one but $400 sounds extreme and a con !
Its only a transformer and few discrete components so $30 should cover it easily.
I buy in UK mains adaptors for £7 at 3 amps.
 
Well , exactly - that's the basis of my previous post, and no reason to disagree having actually measured what a Mojo does internally.

The external supply only feeds an internal switcher to charge the battery up to about 8.4v.
As such I can see that supplying a Mojo with a weedy /crap USB supply that falls below the min 4.75 v DC specified by the USB standard at rated current will increasingly overheat this internal stage. Such SMPS inputs are constant-power, so a weak/ collapsing offboard supply voltage will force such to draw higher current: and that would quickly lead to excess internal dissipation: P loss proportional to I^2, etc.

Just use an USB charger, of reputable quality, of at least 1A capacity. and a good-quality USB charging lead, to minimise voltage drop along its length (again, on a budget Anker are excellent here; may are not, in this regard)