"The Box" monitor speaker ...

Arfa Daily

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Oct 23, 2014, 1:23:36 PM10/23/14

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Got an MA-120 powered monitor speaker from "The Box" (what a shit-street
name for a company ...) in for repair.

The output I.C is blown to pieces, but even before this happened, looks like
it had had the legend ground off it. Anyone happen to know what it is ?

TIA

Arfa

Gareth Magennis

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Oct 23, 2014, 3:01:39 PM10/23/14

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"Arfa Daily" wrote in message news:oQa2w.745511$ZX5....@fx32.am4...

What package is it, and is there a separate amp for the tweeter, or does it
use a passive crossover?

Gareth.

Gareth Magennis

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Oct 23, 2014, 3:06:42 PM10/23/14

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"Gareth Magennis" wrote in message news:kgc2w.519718$XH2.1...@fx23.am4...

http://uk.farnell.com/on-semiconductor/stk404-120n-e/amplifier-audio-class-ab-120w-sip/dp/2400415

Gareth.

N_Cook

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Oct 23, 2014, 4:08:56 PM10/23/14

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Assuming no info out there.
For such situations I determine which are the power rails and output and
ground, "eductaed" guess the inputs , compensation, feedback etc.
Put a sleeved splay-pinned TDA7293 in there and power up at half rail
voltages and see what happens

Gareth Magennis

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Oct 23, 2014, 4:42:02 PM10/23/14

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"N_Cook" wrote in message news:m2bn8e$rn1$1...@dont-email.me...

TDA7293 is a common part in these applications, but the Manufacturers spec
of The Box's 120W RMS @ 4 ohms rules this out, being as the TDA is only
100W.

Unless of course there is a separate 20W amp driving the tweeter.
Or they are lying.

Its probably a Chinese clone of an existing device, hence my Googling and
finding the STK device.

The weird thing is the STK is max rated at 6 ohms. Now, how many 6 ohm
speakers are out there?
Why would you produce such a device and rate it with that output parameter?

(Mind you, I doubt this is the IC in question here, so this is kind of OT)

Gareth.

Arfa Daily

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Oct 23, 2014, 8:26:17 PM10/23/14

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"Gareth Magennis" <gareth....@ntlworld.com> wrote in message
news:qKd2w.526388$_u1.3...@fx30.am4...

TDA7293 is indeed the correct package, so it might be. There is actually an
electrolytic on the opposite end of the board that has also blown apart so
badly that you can't see what value it originally was. The IC has burnt pins
and print as it went up, and deposited a fair bit of soot around. I might
get the IC out tomorrow and clean up a bit and see if it is actually going
to be worth spending the time on. It is basically a piece of Chinese
garbage, and probably not worth very much in the first place. It certainly
isn't in very good condition, and doesn't look like it has been very well
looked after, so it might be time to replace it anyway ...

Arfa

Tim Schwartz

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Oct 24, 2014, 11:43:30 AM10/24/14

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Hi,

Found this link to an owner's manual of the MKII version:

http://images.thomann.de/pics/prod/195950_manual_eng.pdf

The last page as an address and a web address.:

http://www.thomann.de/gb/index.html?sid=aaf669a1b37cdccc73575203df1d90a2

Hope this helps,
Tim
Bristol Electronics