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tech advised better supply for mojo usb charging
tech advised better supply for mojo usb charging
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Old 21st November 2019, 06:52 PM   #1
knifeinthesink is offline knifeinthesink  Canada
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Default 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.
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Old 21st November 2019, 11:37 PM   #2
MAAC0 is offline MAAC0  Portugal
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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.
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Old 22nd November 2019, 02:02 AM   #3
knifeinthesink is offline knifeinthesink  Canada
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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.
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Old 22nd November 2019, 07:10 PM   #4
martin clark is offline martin clark  Europe
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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.
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Old 22nd November 2019, 11:35 PM   #5
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by knifeinthesink View Post
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.
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Old 23rd November 2019, 12:00 AM   #6
knifeinthesink is offline knifeinthesink  Canada
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Thanks for the input. I wanted to be sure that there wasn’t some obvious superior alternative to the plug in phone charger type that I wasn’t aware of. I have some Apple chargers around I gather are stable and clean.
I wasn’t actually considering the $400 charger just to be clear.
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Old 23rd November 2019, 12:02 AM   #7
nigelwright7557 is offline nigelwright7557  United Kingdom
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The problem with using other chargers is they might not be the right voltage or current and could blow up your unit. You need to find the spec of the recommended unit and find one very close.
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Old 23rd November 2019, 09:04 PM   #8
gigigirl is offline gigigirl
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Default Chord Specs

This is the Chord Specs for this unit
Charging:
Mojo can be charged from any 1 Amp USB port using the cable supplied or any other USB A to micro
USB B type cable. Just plug the cable into the connector with the battery symbol.
Please note that the USB charger or computer port must be capable of supplying at least 1A current.

As it charges on board batteries, then any USB charger greater than 1 Amp will do. Should be a no brainer.

Xheers
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Old 23rd November 2019, 09:19 PM   #9
martin clark is offline martin clark  Europe
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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)
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Old 26th November 2019, 02:53 AM   #10
knifeinthesink is offline knifeinthesink  Canada
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Ok. That sounds like the explanation the tech relayed via the shop. I ordered an Anker and I suspect that will do the trick. Thanks.
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