DaveC wrote in
al.net:

The U400 hybrid IC in the Tek 24xx 'scope models is infamous for its
short life.

Has anyone attempted heat-sinking it (if it is not already) and
blowing it with a small fan (a la pentium and PowerPC)?

Just crossed my mind in between random other thoughts...


I haven't heard of anyone doing it,but it would seem to lend itself to
being heatsinked,the metal substrate is exposed on the topside of the
IC,and there's threaded studs to secure a HS. I don't think there's enough
clearance for a fan(cabinet-HS clearance)

It certainly couldn't hurt.
Although,I suspect it's some problem in the die construction itself.
--
Jim Yanik,NRA member
jyanik-at-kua.net

DaveC wrote in
al.net:

On Fri, 21 Nov 2003 17:43:12 -0800, Jim Yanik wrote
(in message ):


I haven't heard of anyone doing it, but it would seem to lend itself
to being heatsinked, the metal substrate is exposed on the topside of
the IC, and there's threaded studs to secure a HS. I don't think
there's enough clearance for a fan (cabinet-HS clearance).

Is U400 accessible w/o removing any PCB's? It sounds like it's on the
outward side of the main board, just beneath the case skin. Is this
true?

Thanks,

Yes,the metal substrate is on the TOP of the IC,exposed,completely
accessable. (but soldered in,40 pin DIP)
All one has to do is coat with HS compound,and bolt the HS to the
studs,IIRC,they're 4-40 thread.I don't think the HS could be more than
perhaps .375" high,though.(SWAG)
You don't want it to contact the cabinet,as I'm not sure if the substrate
is electrically neutral or not.

--
Jim Yanik,NRA member
jyanik-at-kua.net

DaveC wrote in
al.net:

On Fri, 21 Nov 2003 17:43:12 -0800, Jim Yanik wrote
(in message ):


I haven't heard of anyone doing it, but it would seem to lend itself
to being heatsinked, the metal substrate is exposed on the topside of
the IC, and there's threaded studs to secure a HS. I don't think
there's enough clearance for a fan (cabinet-HS clearance).

Is U400 accessible w/o removing any PCB's? It sounds like it's on the
outward side of the main board, just beneath the case skin. Is this
true?

Thanks,

Yes,the metal substrate is on the TOP of the IC,exposed,completely
accessable. (but soldered in,40 pin DIP)
All one has to do is coat with HS compound,and bolt the HS to the
studs,IIRC,they're 4-40 thread.I don't think the HS could be more than
perhaps .375" high,though.(SWAG)
You don't want it to contact the cabinet,as I'm not sure if the substrate
is electrically neutral or not.

--
Jim Yanik,NRA member
jyanik-at-kua.net

DaveC wrote in
al.net:

http://home.covad.net/~peninsula/U400.jpg


That's not the horizontal output IC being discussed,that's the CH2 preamp
hybrid IC.

Odd,but most of the hybrids with this type of HS don't even need a HS,they
don't get warm at all,but the H-output IC doesn't have a HS,yet does get
warm. I guess it's just a fancy package to clamp the hybrid substrate to
the PCB socket.
--
Jim Yanik,NRA member
jyanik-at-kua.net

mike wrote in :

DaveC wrote:
On Sun, 30 Nov 2003 10:16:52 -0800, Jim Yanik wrote
(in message ):


Yes,the metal substrate is on the TOP of the IC,exposed,completely
accessable. (but soldered in,40 pin DIP)
All one has to do is coat with HS compound,and bolt the HS to the
studs,IIRC,they're 4-40 thread.I don't think the HS could be more
than perhaps .375" high,though.(SWAG)
You don't want it to contact the cabinet,as I'm not sure if the
substrate is electrically neutral or not.


-=-=-=-

Hey, what gives? I wasn't expecting this:

http://home.covad.net/~peninsula/U400.jpg

Isn't this already heat-sink'd? I wasn't expecting all the metal. I
don't see how a heat sink could help this situation much. It seems
pretty cool, as is.

This is on a 2465DMS, s/n B051xxx. (And yes, it works. FIne.)

Comments?

Thanks,

Well, it's not a 40-pin dip.
The board sez channel2 preamp.
Methinks you have the wrong U400.

But when you find the right u400, please post that pix.
I don't really want to take mine apart.
mike


IIRC,it was U800 that is the 40 pin DIP horiz output IC.
(and not a hybrid)

--
Jim Yanik,NRA member
jyanik-at-kua.net

mike wrote in :




A couple of thoughts.

What's on the backside of the IC? Do the studs connect to some metal
structure that can act as a heat sink?

edit

I don't know anything about this particular IC.
BUT
In general, when there's a tab, virtually ALL the heat flows out the
tab. Heat sinking the plastic probably won't do any harm and may do
some good IFF you don't hinder the heat flow out the tab.

On this particular IC,the metal substrate is on the TOP side of the IC.Just
right for adding a heat sink! The PCB does not dissipate any heat from the
IC except for what comes thru the leads.I suspect the studs were intended
for a HS that someone else thought unnecessary,or an extra expense.

I would not overtighten those nuts,it might cause IC failure
itself;mechanical strain.


--
Jim Yanik,NRA member
jyanik-at-kua.net

mike wrote in :

Jim Yanik wrote:
mike wrote in :


On this particular IC,the metal substrate is on the TOP side of the
IC.Just
right for adding a heat sink! The PCB does not dissipate any heat
from the
IC except for what comes thru the leads.I suspect the studs were
intended
for a HS that someone else thought unnecessary,or an extra expense.

I would not overtighten those nuts, it might cause IC failure
itself;mechanical strain.


I thought I understood until I read this. According to the pictures and
the previous description, the tab looks like it sits on the board.
There's room to add a nut who's top sits at the level of the IC top???

If there's any room between the tab and the board, the mounting stresses
on the package would be enormous. This assumes the studs go thru the
board. Just occurred to me that the studs could be pressed into the tab
and not go thru the board at all???

the studs are mounted to the PCB.I don't even know why the engineers felt
they needed them.You could leave the nuts off and it would make no
difference.The bottom of the IC plastic package sits right on the PCB,the
substrate IIRC,doesn't hang past the ends of the IC,there's notches in the
ends of the IC for the studs. If I remember right.

--
Jim Yanik,NRA member
jyanik-at-kua.net

DaveC wrote in
al.net:

On Sun, 7 Dec 2003 2:32:09 -0800, Vince wrote
(in message xjFAb.1361$2S4.420@fe10):

Where did you get this heatsink? I'd like to get one to add to my
U800.

Surplus electronics shop here in Sillycon Valley.

I spoke with a Tek engineer who told me that excessive heat was the
failure mode for U800 and that heatsinking it is a good idea, so I
think you're on the right track.

Intuitively, it just seemed like the right decision.

I know someone else who heatsinked his U800 and hasn't had any
problems so far. The only caveat he said is the studs are at -5V so
one has to be sure that the heatsink doesn't touch the case...

There are little vinyl "nipples" that slip over the studs to insulate
them. Just be sure to put them back on when you've finished the job.
Might be prudent to trim those nipples to accomodate the additional
height of the nuts and heat sink. Not much, just a few mm.

There is a flat cable connector that plugs onto header J102; you can
see the header pins in this photo:

http://home.covad.net/~peninsula/Before.jpg

It's easy to pull the connector off. I didn't notice, and got
Counter/Timer option errors on startup. (If you don't have C/T option,
might not have this connector; don't know...). Also was told that it
is common to pull off one of the coax cables running through this
area, which gives similar power-on diagnostics errors.

If the option(s) are not installed,or does not require a signal
pickoff,there are jumpers that are installed;see your schematic for the
vertical section.

--
Jim Yanik,NRA member
jyanik-at-kua.net

DaveC wrote in
al.net:

On Mon, 8 Dec 2003 9:16:41 -0800, John Woodgate wrote
(in message ):

Yes, I want to get the heat from the tab to the bottom of the heat
sink, a distance of about 1.2 mm. Thermal properties count.

Incidentally, I make heat sinks for my own stuff and
repairs/improvements out of bits of scrap copper water pipe.

Copper sounds ideal. I'm sure I could find a piece of copper that
thickness.

Thanks,

Looking at the pix on your site,it seems to me you have adequate contact
already.Maybe if you can find a surplus HS a tad longer,sure,go ahead,but I
doubt you'll gain much in dissipation over what you have now.
IMO,a different style HS with fins closed to the center of the IC substrate
would be best,as the HS cross-section(thickness) limits what heat gets
dissipated.
But hey,it's your scope.

--
Jim Yanik,NRA member
jyanik-at-kua.net

DaveC wrote in
al.net:

On Mon, 8 Dec 2003 21:51:30 -0800, DaveC wrote
(in message et):

The contact between the tab and my heat sink is provided by a #4-40
nut. The nut is come kind of steel, not real flat on either side. It
is about
maybe
50 percent of the area of the tab.

And my heat sink doesn't even cover the nut completely. Looking at the
photo, the heat sink ends before it extends completely under the nut:

http://home.covad.net/~peninsula/After.jpg

The heat sink covers the majority of the IC, but that's mostly
plastic, and the heat is radiated mostly by the two exposed metal
parts.

it needs reworking...

ISTR that the metal substrate is exposed on the top side of the IC for most
of the length of the IC.
You should be getting pretty decent thermal contact.

--
Jim Yanik,NRA member
jyanik-at-kua.net

Jim Yanik wrote:
DaveC wrote in
al.net:


On Mon, 8 Dec 2003 21:51:30 -0800, DaveC wrote
(in message et):


The contact between the tab and my heat sink is provided by a #4-40
nut. The nut is come kind of steel, not real flat on either side. It
is about

maybe

50 percent of the area of the tab.

And my heat sink doesn't even cover the nut completely. Looking at the
photo, the heat sink ends before it extends completely under the nut:

http://home.covad.net/~peninsula/After.jpg

The heat sink covers the majority of the IC, but that's mostly
plastic, and the heat is radiated mostly by the two exposed metal
parts.

it needs reworking...


ISTR that the metal substrate is exposed on the top side of the IC for most
of the length of the IC.
You should be getting pretty decent thermal contact.


Jim, I'm really confused by this.
Are we looking at the same picture?
http://home.covad.net/~peninsula/Before.jpg
If the terms "metal substrate" and "tab" are different terms for
the same heat sink structure of the IC, your statement conflicts with
the picture.
What am I missing?
mike

--
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S
TEK Sampling Sweep Plugin and RM564
Tek 2465 $800, ham radio, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

mike wrote in :

Jim Yanik wrote:
DaveC wrote in
al.net:


On Mon, 8 Dec 2003 21:51:30 -0800, DaveC wrote
(in message et):


The contact between the tab and my heat sink is provided by a #4-40
nut. The nut is come kind of steel, not real flat on either side. It
is about

maybe

50 percent of the area of the tab.

And my heat sink doesn't even cover the nut completely. Looking at
the photo, the heat sink ends before it extends completely under the
nut:

http://home.covad.net/~peninsula/After.jpg

The heat sink covers the majority of the IC, but that's mostly
plastic, and the heat is radiated mostly by the two exposed metal
parts.

it needs reworking...


ISTR that the metal substrate is exposed on the top side of the IC
for most of the length of the IC.
You should be getting pretty decent thermal contact.


Jim, I'm really confused by this.
Are we looking at the same picture?
http://home.covad.net/~peninsula/Before.jpg
If the terms "metal substrate" and "tab" are different terms for
the same heat sink structure of the IC, your statement conflicts with
the picture.
What am I missing?
mike


OK,I was thinking(perhaps it's the earlier version I recall) that the metal
substrate was exposed for the whole length of the IC,not just the tab.
My fault.
So,what I would do is cut a small square piece of sheet copper(or
aluminum),drill a hole for the stud,place it between the tab and the HS,and
a smaller one for the narrow slot,use thermal grease,too.Or trim a copper
washer to size.
Perhaps an old penny? not the new zinc ones.

Heck,maybe THATS why the IC is prone to failure;they changed the packaging
and thermal dissipation with a full plastic DIP package,instead of the
bared substrate IC as ISTR.
(Of course,being an old geezer,my memory sometimes fails me) 8-)

--
Jim Yanik,NRA member
jyanik-at-kua.net