Owner says working , then stored indoors for a few months while at uni
and now although bar graph functions etc, no sound in the speakers. I
tried it and the same.
In the bottom of the case a piece of PPE, sheared off in one piece but
not the whole encapsulation, from one of the mains SMPS 6 pin combined
controller and powerFET devices.
A TOP249YN. As that side powers main +rail of the PAs and the unit does
not go into protect, I'm assuming that and the other TOP249Y are in
working order and some short-term stress blew off the PPE sometime back
in its working history. Under x30 you can see a striated part of the die
and no sign of burning or sputtering anywhere on either part. Heat with
110 deg C hot air, to expel humidity , then a piece of mica and then a
covering of RTV ?
or Grind back any awkward bits of the retrieved section and glue back
with RTV , only on the outside,
or use RTV on the inside , so in contact with the die (after hot-airing
that is)

Otherwise the PAs seem ok on cold DVM-D testing and at least one failed
PbF solder join found, 20 to 100 ohm, on the notorious wobbly union of
boards is probably the recent failure mechanism, the music/speech sw
seems ok

"N_Cook" wrote in message
...
Owner says working , then stored indoors for a few months while at uni and
now although bar graph functions etc, no sound in the speakers. I tried it
and the same.
In the bottom of the case a piece of PPE, sheared off in one piece but not
the whole encapsulation, from one of the mains SMPS 6 pin combined
controller and powerFET devices.
A TOP249YN. As that side powers main +rail of the PAs and the unit does
not go into protect, I'm assuming that and the other TOP249Y are in
working order and some short-term stress blew off the PPE sometime back in
its working history. Under x30 you can see a striated part of the die and
no sign of burning or sputtering anywhere on either part. Heat with 110
deg C hot air, to expel humidity , then a piece of mica and then a
covering of RTV ?
or Grind back any awkward bits of the retrieved section and glue back with
RTV , only on the outside,
or use RTV on the inside , so in contact with the die (after hot-airing
that is)


Why on earth would you arsehole about sticking the bloody lid back on the
TOP chip ? Those things are pence. In fact I'm surprised you don't actually
have them in stock. Just replace it and be done with it. Then there will be
no question about how and why the lid came to be rolling about in the bottom
of the unit, and whether or not it could be / might be / probably / is /
isn't ****ted ...

Arfa



Otherwise the PAs seem ok on cold DVM-D testing and at least one failed
PbF solder join found, 20 to 100 ohm, on the notorious wobbly union of
boards is probably the recent failure mechanism, the music/speech sw seems
ok

On 31/07/2014 01:58, Arfa Daily wrote:


"N_Cook" wrote in message
...
Owner says working , then stored indoors for a few months while at uni
and now although bar graph functions etc, no sound in the speakers. I
tried it and the same.
In the bottom of the case a piece of PPE, sheared off in one piece but
not the whole encapsulation, from one of the mains SMPS 6 pin combined
controller and powerFET devices.
A TOP249YN. As that side powers main +rail of the PAs and the unit
does not go into protect, I'm assuming that and the other TOP249Y are
in working order and some short-term stress blew off the PPE sometime
back in its working history. Under x30 you can see a striated part of
the die and no sign of burning or sputtering anywhere on either part.
Heat with 110 deg C hot air, to expel humidity , then a piece of
mica and then a covering of RTV ?
or Grind back any awkward bits of the retrieved section and glue back
with RTV , only on the outside,
or use RTV on the inside , so in contact with the die (after
hot-airing that is)


Why on earth would you arsehole about sticking the bloody lid back on
the TOP chip ? Those things are pence. In fact I'm surprised you don't
actually have them in stock. Just replace it and be done with it. Then
there will be no question about how and why the lid came to be rolling
about in the bottom of the unit, and whether or not it could be / might
be / probably / is / isn't ****ted ...

Arfa



Otherwise the PAs seem ok on cold DVM-D testing and at least one
failed PbF solder join found, 20 to 100 ohm, on the notorious wobbly
union of boards is probably the recent failure mechanism, the
music/speech sw seems ok


Not on RS which is the only supply company I have an account with. At
the moment may as well stay with what is there than take the pirate-ebay
chance for this sort of device.
slant-on pic (large cap in the way) of what remains
http://www.diverse.4mg.com/top249.jpg
presumably the striations are a heat dissipative section

Looks like porkies from the owner. Main +V rail is missing from the PAs
but the -V rail is present. Looks as though only one SMPS is working and
the protect circuit does not monitor rail imbalance (or protect circuit
is powered solely from the blown SMPS )
So I will have to get at least one of those drivers

"N_Cook" wrote in message
...
Looks like porkies from the owner. Main +V rail is missing from the PAs
but the -V rail is present. Looks as though only one SMPS is working

Now there's a surprise ...


and
the protect circuit does not monitor rail imbalance (or protect circuit is
powered solely from the blown SMPS )
So I will have to get at least one of those drivers


Why not push the boat out, and get TWO, Nigel ...?

Arfa

On 31/07/2014 12:23, Arfa Daily wrote:


"N_Cook" wrote in message
...
Looks like porkies from the owner. Main +V rail is missing from the
PAs but the -V rail is present. Looks as though only one SMPS is working

Now there's a surprise ...


and
the protect circuit does not monitor rail imbalance (or protect
circuit is powered solely from the blown SMPS )
So I will have to get at least one of those drivers


Why not push the boat out, and get TWO, Nigel ...?

Arfa

I forgot to say the mixer section works as output at line-out.

The first ebay actual geographic UK supplier I found
7,000 good feedback from buyers
0 neutral
0 negative
why does that look highly suspicious to me?
Next was China with .co.uk URL, blah blah blah