ART Tube MP Studio V3 Mic Instrument Preamp 12AX7A Valve Vacuum
 

I found this item listed in a eBag auction, listed as not-working missing
parts etc.

Chancing that the unit was repairable (how hard could it be? as they say on
Top Gear) I bought said non-working unit.

So I naturally took it completely apart for a looky-see.. man, that's a lot
of electrolytic caps, but no components burned or missing from the boards,
at least.

The auction mentioned that the 12AX7A tube was missing, although I wasn't
too worried since I had a new 12AU7 (Japan) that I've been keeping in a
parts drawer for decades (acquired the tube in 1973).
Good enuff for checking out the operation, and possibly a better choice for
cleaner sound.

The steel case of these products is very impressive, although a bit "school
of design" more stylish than practical, IMO.

Applied 9VAC to the power connector and saw some LED and panel meter
activity, but the tube filaments weren't lit and I noticed that the
multistrand ribbons connecting the front controls board to the main board
were abnormally flexible.. not even stiff enough to support the weight of
the small controls board without bending.

Apparently some previous user had opened the case for some reason, and may
have flexed the ribbons enough to break some of the wires.
It turned out that the stranded conductors are tinned (soldered) along their
entire length before embedding them in the plastic jacket material, so
they're especially susceptable to breakage from flexing/movement at the
exposed ends.

I applied a small bead of hot glue along the ends of the ribbons where
they're soldered to the main board to reinforce the ribbon jacket, securing
them to the board.

I trimmed and stripped the opposite ends, desoldered all the broken original
ends from the board, and resoldered the ribbons to the small front control
board.. followed by a small bead of hot glue to reinforce the connection.

I wasn't familiar with this product, but was happy to see that there weren't
any microprocessor or custom ICs used in it's design. A couple of opamps and
a ****load of caps makes up much of the circuitry.

One of the main upgrade/modification reccomendations found in online forums,
is to replace the original China tube with something more deserving of a
perceived level of reliability (or much better sound, according to some
opinions). I'm no recording specialist, so I don't know.

Just opening/separating the case halves causes flexing of the ribbons for
the front control board, unless the knobs and nuts are removed from the
Input and Output pots, so breakage of the ribbons is likely to happen if the
case is opened and handled carelessly, or opened repeatedly over time.

Wowwy-zowwy.. to think I almost bought a new base model with less features,
for more money (only slightly).

--
Cheers,
WB
..............