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

Talk of pirated components. Now extracted and laying the device on a
flat surface, it rocks, the backing metal copper slab has a curve in the
sense that it will not flatten out on tightening the bolt.
No indication of the white goo overheating , but what temp to
permanently deform copper? probably made like that and poor heat
conduction to the heatsink proper.

On Thu, 31 Jul 2014 13:24:04 +0100 N_Cook wrote in
Message id: :

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?

They only count the last 12 months. I have a 100% seller rating with 562
feedbacks as well, and 5 stars on 4 categories + a 4.9 stars on the fifth.
(but never had a bad feedback at all, even going back to the beginning)

You do have to work hard to keep customers happy.

"N_Cook" wrote in message
...
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


You're just a suspicious cynic. The guy that I use for most of my bits has
over 16000 feedback, and only a very few neutrals and negatives. How do you
suppose that the person that you looked at managed to arrange 7000
fraudulent "good" feedbacks ? And if you really believe that they are, then
you should do your civic duty on behalf of us all, and report him ...

Arfa

"N_Cook" wrote in message
...
Talk of pirated components. Now extracted and laying the device on a flat
surface, it rocks, the backing metal copper slab has a curve in the sense
that it will not flatten out on tightening the bolt.
No indication of the white goo overheating , but what temp to permanently
deform copper? probably made like that and poor heat conduction to the
heatsink proper.


So, does it look like it's been replaced before ? If not, then it must be an
original Yammy fitted part, and if they can't get it right sourcing their
bits, what makes you think that anything that you buy from eBay, or a
Chinese supplier, is going to be any worse than that ? And if you think that
it has overheated, either by itself, or by virtue of the fact that it was
bent when originally installed, then why would the paste be showing no signs
of overheating ?

Arfa

On 31/07/2014 14:53, JW wrote:
On Thu, 31 Jul 2014 13:24:04 +0100 N_Cook wrote in
Message id: :

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?

They only count the last 12 months. I have a 100% seller rating with 562
feedbacks as well, and 5 stars on 4 categories + a 4.9 stars on the fifth.
(but never had a bad feedback at all, even going back to the beginning)

You do have to work hard to keep customers happy.


I don't know what the statistics are but all the times packages
disappear in the post, wrongly transcribed addresses, pilfering within
the postal system etc. I used to go to viewings of the monthly auctions
of all the packages (not lettters) stuff that could not be delivered by
the UK Royal Mail in southern England, returned to Portsmouth at one
time. In terms of volume about 50 cubic metres a month.
But those situations are always interpretted by customers as faults
of the supplier, so where are all those negative feedbacks ?

On 31/07/2014 16:02, Arfa Daily wrote:


"N_Cook" wrote in message
...
Talk of pirated components. Now extracted and laying the device on a
flat surface, it rocks, the backing metal copper slab has a curve in
the sense that it will not flatten out on tightening the bolt.
No indication of the white goo overheating , but what temp to
permanently deform copper? probably made like that and poor heat
conduction to the heatsink proper.


So, does it look like it's been replaced before ? If not, then it must
be an original Yammy fitted part, and if they can't get it right
sourcing their bits, what makes you think that anything that you buy
from eBay, or a Chinese supplier, is going to be any worse than that ?
And if you think that it has overheated, either by itself, or by virtue
of the fact that it was bent when originally installed, then why would
the paste be showing no signs of overheating ?

Arfa

Looks original soldering to me. Maybe a couple of reworked minor SMD
elsewhere
If the overheating was very short lived, then perhaps no time for any
external signs but enough energy to shatter the die as the heat could
not exit quick enough. I will try and measure the curvature.

10.4mm wide rear tab. Holding one side down on a piece of mirror glass
then I can just enter 0.09mm of feeler gauges into the gap on the other
side. No idea what that curvature means for sillypads and heat transfer.

"N_Cook" wrote in message
...
10.4mm wide rear tab. Holding one side down on a piece of mirror glass
then I can just enter 0.09mm of feeler gauges into the gap on the other
side. No idea what that curvature means for sillypads and heat transfer.


So what's that then ? 90 microns is it ? I wouldn't have thought that was
particularly significant, particularly if the heat transfer medium was a
pad.

Arfa

"N_Cook" wrote in message
...
On 31/07/2014 14:53, JW wrote:
On Thu, 31 Jul 2014 13:24:04 +0100 N_Cook wrote in
Message id: :

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?

They only count the last 12 months. I have a 100% seller rating with 562
feedbacks as well, and 5 stars on 4 categories + a 4.9 stars on the
fifth.
(but never had a bad feedback at all, even going back to the beginning)

You do have to work hard to keep customers happy.


I don't know what the statistics are but all the times packages disappear
in the post, wrongly transcribed addresses, pilfering within
the postal system etc. I used to go to viewings of the monthly auctions of
all the packages (not lettters) stuff that could not be delivered by the
UK Royal Mail in southern England, returned to Portsmouth at one time. In
terms of volume about 50 cubic metres a month.
But those situations are always interpretted by customers as faults of
the supplier, so where are all those negative feedbacks ?


I've been buying **** off of eBay for probably ten years now, and in all
that time, I have only had one package not turn up in the time expected -
and that includes many items bought from China. And as it happens, the
errant parcel did actually turn up about a week later, after the company had
sent a replacement out, following a 'private' contact to them. I most
certainly didn't leave them bad feedback, as the non-delivery obviously
wasn't their problem, and they went out of their way to resolve the problem
as quickly as possible. As JW commented, you have to work hard at customer
service. I have been selling on eBay for quite some time, and I also have
never received bad feedback .

As I commented elsewhere, how do you think it would be possible for your
seller to have arranged for himself to get all this feedback in a fraudulent
way ?

Arfa

On 01/08/2014 01:56, Arfa Daily wrote:


"N_Cook" wrote in message
...
On 31/07/2014 14:53, JW wrote:
On Thu, 31 Jul 2014 13:24:04 +0100 N_Cook wrote in
Message id: :

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?

They only count the last 12 months. I have a 100% seller rating with 562
feedbacks as well, and 5 stars on 4 categories + a 4.9 stars on the
fifth.
(but never had a bad feedback at all, even going back to the beginning)

You do have to work hard to keep customers happy.


I don't know what the statistics are but all the times packages
disappear in the post, wrongly transcribed addresses, pilfering within
the postal system etc. I used to go to viewings of the monthly
auctions of all the packages (not lettters) stuff that could not be
delivered by the UK Royal Mail in southern England, returned to
Portsmouth at one time. In terms of volume about 50 cubic metres a month.
But those situations are always interpretted by customers as faults
of the supplier, so where are all those negative feedbacks ?


I've been buying **** off of eBay for probably ten years now, and in all
that time, I have only had one package not turn up in the time expected
- and that includes many items bought from China. And as it happens, the
errant parcel did actually turn up about a week later, after the company
had sent a replacement out, following a 'private' contact to them. I
most certainly didn't leave them bad feedback, as the non-delivery
obviously wasn't their problem, and they went out of their way to
resolve the problem as quickly as possible. As JW commented, you have to
work hard at customer service. I have been selling on eBay for quite
some time, and I also have never received bad feedback .

As I commented elsewhere, how do you think it would be possible for your
seller to have arranged for himself to get all this feedback in a
fraudulent way ?

Arfa

Auction houses have always accepted bids from the chandeliers, so
anything is possible.
The numbers just look highly suspicious, like those "democracies" where
the incumbent gets back in with a 97% election result in their favour,
or Kent Police who had something like a 114% burglary clear-up rate one
year.

On 01/08/2014 01:37, Arfa Daily wrote:


"N_Cook" wrote in message
...
10.4mm wide rear tab. Holding one side down on a piece of mirror glass
then I can just enter 0.09mm of feeler gauges into the gap on the
other side. No idea what that curvature means for sillypads and heat
transfer.


So what's that then ? 90 microns is it ? I wouldn't have thought that
was particularly significant, particularly if the heat transfer medium
was a pad.

Arfa

All the white goo made it look like sillypads, but I just removed it and
its mica sheet.
Yes, the rocking looked bad but measurement looks tiny, how the cookie
crumbles.

On 01/08/2014 08:42, N_Cook wrote:
On 01/08/2014 01:37, Arfa Daily wrote:


"N_Cook" wrote in message
...
10.4mm wide rear tab. Holding one side down on a piece of mirror glass
then I can just enter 0.09mm of feeler gauges into the gap on the
other side. No idea what that curvature means for sillypads and heat
transfer.


So what's that then ? 90 microns is it ? I wouldn't have thought that
was particularly significant, particularly if the heat transfer medium
was a pad.

Arfa

All the white goo made it look like sillypads, but I just removed it and
its mica sheet.
Yes, the rocking looked bad but measurement looks tiny, how the cookie
crumbles.

Another thing to add to the autopsy. The retaining screw on this one
needed 1/4 turn to tighten, 1/8 on the surviving one. Not loose as a
spring washer on each but only the applied force of a half compressed
spring washer, plus rigid mica and curving could have meant failure
sometime in normal use.

Auction houses have always accepted bids from the chandeliers, so anything
is possible.
The numbers just look highly suspicious, like those "democracies" where
the incumbent gets back in with a 97% election result in their favour, or
Kent Police who had something like a 114% burglary clear-up rate one year.


If you think that eBay don't have automated software running to spot this
sort of thing, then you really are a bit naiive as to the way they work.
Trust me, nothing gets by them.

Arfa

7001 implied positive supplier feedback I suppose, now.
This driver has no curved back, same logo , but different typography,
whether that means anything I'll assume not.
Isolated PS + PAs board now has clicking relay and full +/- rails on the
PAs , so time to reassemble it all and full testing.
Just one remaining poser. The owner insists , the last time it was used
was with 2 mic inputs only and low level of output.
I suppose it is just possible that with the long-term mechanical
stressing to the PPE , because of the bowed backing, and heat build up,
then a switch-off imbalance surge could have been the final straw and
the encapsulation breaking at that point , plus a die failure, and any
noise would be disguised as normal speaker switch-off pop or 2.

back working again.
In case 1 or more devices were pirated, a pic
http://diverse.4mg.com/TOP249.jpg
left one RTV survived the desoldering, normal datecode plastic mould
mark and overlay "7segment" date of 2012, right one different datecode
structure