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I was misdirected about this but will ask here if anyone has any knowledge. Told intermittant output so assumed mechanical socket failure. USB powered SMD digital mixer thingy. Everything about this looks suspect except the quality of assembly which is fine for China made, 2004 Make MBOX, model MBOX Googling the "tick" compliance number "ACN 069 650 120" produces zilch. Under a magnifier chippery such as Fairchild, TI, Philips , but under x30 they are blotchy printed bogus mock logos of F, the Texas state and sonogram logo of Philips and just numbers not likes of ABnnnn type numbers. Without pc drivers etc I doubt this one is going anywhere , but just in case anyone knows of a stock fault producing a hash output with no hint of signal throughput

Reply to
N_Cook
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with USB connected but no active pc. Hash on both channels of headphone monitoring, cycling through on about 1.1 sec period. Worse when phantom is on so maybe something with the 5 to 48V generator. Will try a few IC numbers to check DC rails, check ESR of caps and disable unused 48V supply is about as far as I will go.

Reply to
N_Cook

Isn't the Mbox Mac only?

Gareth.

Reply to
Gareth Magennis

Er, scratch that, it is, but I think its a bit fussy on what it will and won't work with.

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Gareth.

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Reply to
Gareth Magennis

is

It was working with whatever flavour of pc until this hash developed. No trace of 48V anywhere. XLR mic connections traced via 6.2K droppers back to the rectifier diode of the buck converter. Looks as though the output is gated rather than converter switched on and off for phantom. Will try locating data on this dodgey looking labelled soic and cut its supply anyway and hope it is not monitored by anything

Reply to
N_Cook

That was going to be my next question - whether this suddenly stopped working in a working system, or if the guy had just bought it off ebay and couldn't get it to work.

Mind you, at this kind of price for a much better unit that probably works in all PC's, why bother paying for a repair?

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Reply to
Gareth Magennis

"Nutcase Kook" <

** The C-tick is the Aussie designation for EMC compliance - required on nearly all electronic devices sold here and the CE logo counts for nothing. The ACN number refers to "Avid Technology Australia Pty Ltd " first registered here in 1995 - no doubt as an import agent for Avid products.

Seems Avid stick all the compliance logos and required numbers for every country on each Mbox.

.... Phil

Reply to
Phil Allison

There are threads out there on MBOX noise problems and caps. Putting 2,000uF,10V across the USB supply seems to near enough cure it, is that permissable, wrt USB spcifications? nonly a measly 10uF or so there as far as I can see. There are 4 LDO regs MIC5205B, topmarked LBAA, 3 hold their outputs but one varies 30mV timed with the hash variation, Putting the cap there makes a vast improvement but not quite up to the main supply smoothing. Will try tracing all caps to that reg and replace them.

Reply to
N_Cook

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