On 08/02/2014 13:55, N_Cook wrote:
On 08/02/2014 13:48, N_Cook wrote:
No function including no LEDs.
Failed 3.3V VR, ominously tested no load as 4V, maybe normal , will
have to try some known gooders
About 1.5 ohm ground to 3.3V rail. Found where the confusing inner 3.3V
plane came off (near IC9) cutting either side of there and a couple of
other places, limited to one area of board.
Powering with V and A limited bench ps set for 3V limit, taking .2A,
dropped .4V and .3A dropped .7V.
With IR thermometer I would have thought 0.2W would shine out , about 1
degree C only above, around IC4 and AKM 4552VT codec, Japanese datasheet
out there. From that I think I know where to cut its supply trace,
despite being under the IC.
Anyone been here before ?, the main Roland chips are dead cold.
Anyone know what 5 pin SC70-5 or SOT416 format IC top coded JAPN is,
just in passing, googling got nowhere ?
Reminder to myself when using IR thermometer - use a distant LED torch
to illuminate the board. Misled into "finding" a faulty main cap , as
heating up a few degrees in one area of the cap, despite no normal
connection to any 3V line. My flourescent lamp was reflecting heat off
the cap top. Even turning off the lamp made no difference , retained
heat of course.
Also handled a switch and 3 seconds later found a (phantom) hot spot
there.
No change in ohmage heating or freezing.
I don't fancy removing a 16p IC, where it is, even if a replacement was
available, but now I've got this far I have to follow it through to
the end

The J of 4 letter code JAPN has 2 dots over .
My IR thermo has a conical reflector to the pyro, just the right size to
test each of the couple of dozen radial electros, by placing end of cap
in the cone, and no excess over ambient

Isolated that IC and still low ohms load on 3.3V line. About all that
was left to cut was area of the big BOSS chippery.
Cut line to p38 of 80 pin R02565501 and inside that was the low ohms, so
end of the road I think. Perhaps a thin trace 3.3V or ground line runs
under the AKM 16 pinner.
Perhaps I'll solder a wire to p38 and drive again with some less
constrained current and see what happens with IR monitoring, for
edification. First Cube Roland main chip failure like this I've come
across, 2 stomp boxes before IIRC