IC overheating.

[[email protected]]

I'm working on a little fanspeed regulator circuit. This specified
debouncing circuit wasn't working at all (bad switch?), so I
substituted a design known to work that used a not-gate (LS04). It
warks fine, but the problem is that the LS04 chip heats up pretty
quickly, then eventually gets too hot to leave it plugged in. I
searched the layout, and checked all the connections, but couldn't
find any shorts or bad connections. I had a different chip before (I
think a display driver) that was set up propperly on a breadboard but
burned up too, leading be to believe that it was just a bad chip. So
its possible that the chip I have (04) is just bad, and may have been
damaged during soldering. Does this theory fly with any body else?

Is there anyhing I can do to fix it without using another chip? Ground
outputs, etc? Has anybody had a 'bad' chip that burns up right out of
the box? Does the idea of soldering sound like a cause of overheating?

Cheers.

 

[John Popelish]

I'm working on a little fanspeed regulator circuit. This specified
debouncing circuit wasn't working at all (bad switch?), so I
substituted a design known to work that used a not-gate (LS04). It
warks fine, but the problem is that the LS04 chip heats up pretty
quickly, then eventually gets too hot to leave it plugged in. I
searched the layout, and checked all the connections, but couldn't
find any shorts or bad connections. I had a different chip before (I
think a display driver) that was set up propperly on a breadboard but
burned up too, leading be to believe that it was just a bad chip. So
its possible that the chip I have (04) is just bad, and may have been
damaged during soldering. Does this theory fly with any body else?

Is there anyhing I can do to fix it without using another chip? Ground
outputs, etc? Has anybody had a 'bad' chip that burns up right out of
the box? Does the idea of soldering sound like a cause of overheating?

Cheers.

Assuming power is applied to the right pins, the only load
situation that normally heats up TTL is to have an output
tied to the positive rail. Of course, inputs or outputs
connected to voltages outside the rails may cause the chip
to turn into and SCR that shorts the supply rails.

 

[Eeyore]

I'm working on a little fanspeed regulator circuit. This specified
debouncing circuit wasn't working at all (bad switch?), so I
substituted a design known to work that used a not-gate (LS04).

That's normally called an inverter. 'Academics' might call it a not gate
perhaps. They're normally fairly out of touch with reality as a rule.

It
warks fine, but the problem is that the LS04 chip heats up pretty
quickly, then eventually gets too hot to leave it plugged in. I
searched the layout, and checked all the connections, but couldn't
find any shorts or bad connections. I had a different chip before (I
think a display driver) that was set up propperly on a breadboard but
burned up too, leading be to believe that it was just a bad chip. So
its possible that the chip I have (04) is just bad, and may have been
damaged during soldering. Does this theory fly with any body else?

Where's your schematic ?

Is there anyhing I can do to fix it without using another chip? Ground
outputs, etc? Has anybody had a 'bad' chip that burns up right out of
the box? Does the idea of soldering sound like a cause of overheating?

Not unless your soldering is really bad.

Graham

 

[[email protected]]

That's normally called an inverter. 'Academics' might call it a not gate
perhaps. They're normally fairly out of touch with reality as a rule.

Obviously. Is a car an automobile? Perhaps a transportation vector
would be more 'academic'. And it's technically a "Hex-Inverter"
anyway. Burn.

Where's your schematic ?

The base design is located at:
http://www.usenet-replayer.com/cgi/content/viruscheck?/9/8/1/3/1171353189.59.pdf

However the input/debouncing circut is completely different in my
implementation. Also, I only have four output states, not five.

Not unless your soldering is really bad.

The soldering suggestion was implying that I may have baked it. I did
heat-shield the pins and all, but it is possible that I botched
something, especially at 3am and all. I wanted to know if a baked
chip could be prone to internal voltage shorts.

 

[Eeyore]

Obviously. Is a car an automobile? Perhaps a transportation vector
would be more 'academic'. And it's technically a "Hex-Inverter"
anyway. Burn.

In which case you should have said a hex not-gate !

The base design is located at:
http://www.usenet-replayer.com/cgi/content/viruscheck?/9/8/1/3/1171353189.59.pdf

No it's not !

How about a link that works ?

However the input/debouncing circut is completely different in my
implementation. Also, I only have four output states, not five.


The soldering suggestion was implying that I may have baked it. I did
heat-shield the pins and all, but it is possible that I botched
something, especially at 3am and all. I wanted to know if a baked
chip could be prone to internal voltage shorts.

A 'baked' chip could do anything but you have to be pretty clumsy to to that.

Graham

 

[[email protected]]

Tripple quotes? You're taking time to help, so I'll play nice

As far as the schema goes, go here:

http://www.usenet-replayer.com/groups/alt.binaries.schematics.electronic.html

and search (link at bottom) for "fanspeed". You'll see two versions,
an old and a new.

Cheers.

 

[Eeyore]

Tripple quotes? You're taking time to help, so I'll play nice

Yes you should.

As far as the schema goes, go here:

http://www.usenet-replayer.com/groups/alt.binaries.schematics.electronic.html

and search (link at bottom) for "fanspeed". You'll see two versions,
an old and a new.

Neither have a 7406.

Graham

 

[Andy]

On 18 Feb, 09:00, [email protected] wrote:
Hi,

As far as I can tell both the schematics are the same and don't
include a HC04 inverter.

However assuming the chip where you described, is not damaged, is
connected to correct rails and has been decoupled. My guess would be
that as you have probably only used one of the inputs and the others
are floating. They tend to float to the mid rail and often oscillate a
bit this causes masses of power to be used as it switches backwards
and forwards in the region where both the transistors in the output
are on for a short time.

If this is the case all you need to do is make sure all the unsued
inputs are tied to ground / 0v (CMOS parts like the HC only). If the
part is not decoupled a 100nF between power and ground will help to
reduce the oscillations for unconected inputs but even when they are
all grounded its good practice and will reduce the chance of switch
bounce.

To further reduce the chance of switch bounce I would recomend
changing to a HC14 part as this has a schmitt trigger input. This has
different threasholds for rising and falling signals so there is a
region after it has changed state that even if it does drop back a
little due to noise it won't change state again. Again unused inputs
should be tied to ground although this is less of a problem with
schmitt triggers.

Regards,
Andrew

 

[neon]

no bad soldering can cause heat up and still working. my bid is that it is oscillating at some very hi frequency for some design or introduced signal. that will make it heat up. LS are fast devices try a 7404 same function without the speed. with a fast scope you could verify the oscillations.

 

[colin]

I'm working on a little fanspeed regulator circuit. This specified
debouncing circuit wasn't working at all (bad switch?), so I
substituted a design known to work that used a not-gate (LS04). It
warks fine, but the problem is that the LS04 chip heats up pretty
quickly, then eventually gets too hot to leave it plugged in. I
searched the layout, and checked all the connections, but couldn't
find any shorts or bad connections. I had a different chip before (I
think a display driver) that was set up propperly on a breadboard but
burned up too, leading be to believe that it was just a bad chip. So
its possible that the chip I have (04) is just bad, and may have been
damaged during soldering. Does this theory fly with any body else?

Is there anyhing I can do to fix it without using another chip? Ground
outputs, etc? Has anybody had a 'bad' chip that burns up right out of
the box? Does the idea of soldering sound like a cause of overheating?

Sounds like they overfilled the chips with magic smoke, has any escaped yet
?

dont ground outputs, but ground any unused inputs, make sure outputs arnt
overloaded, and supply voltage or any other inputs havnt got any over
voltage peaks etc.

Colin =^.^=

 

[Rich Grise]

I'm working on a little fanspeed regulator circuit. This specified
debouncing circuit wasn't working at all (bad switch?), so I
substituted a design known to work that used a not-gate (LS04). It
warks fine, but the problem is that the LS04 chip heats up pretty
quickly, then eventually gets too hot to leave it plugged in. I
searched the layout, and checked all the connections, but couldn't
find any shorts or bad connections. I had a different chip before (I
think a display driver) that was set up propperly on a breadboard but
burned up too, leading be to believe that it was just a bad chip. So
its possible that the chip I have (04) is just bad, and may have been
damaged during soldering. Does this theory fly with any body else?

Is there anyhing I can do to fix it without using another chip? Ground
outputs, etc? Has anybody had a 'bad' chip that burns up right out of
the box? Does the idea of soldering sound like a cause of overheating?

I've had chips get too hot to touch by plugging them in backwards. =:-O

Good Luck!
Rich

 

[Lionel]

I'm working on a little fanspeed regulator circuit. This specified
debouncing circuit wasn't working at all (bad switch?), so I
substituted a design known to work that used a not-gate (LS04). It
warks fine, but the problem is that the LS04 chip heats up pretty
quickly, then eventually gets too hot to leave it plugged in. I
searched the layout, and checked all the connections, but couldn't
find any shorts or bad connections. I had a different chip before (I
think a display driver) that was set up propperly on a breadboard but
burned up too, leading be to believe that it was just a bad chip. So
its possible that the chip I have (04) is just bad, and may have been
damaged during soldering. Does this theory fly with any body else?

More likely the unused gates are oscillating, or you're pulling too
much current from the gate that you are using. Try tying all your
unused inputs together & connecting them to +5V with a 4K7 resistor.
Also check that Vcc (pin 14) is really at +5V relative to the ground
pin (pin 7).

 

[jasen]

I've had chips get too hot to touch by plugging them in backwards. =:-O

I've had them work afterwards. (it was a 7555)

 

[[email protected]]

This thing is getting on my nerves. I got some wire and stuff, and
made a breadboard to molex adapter, and it worked flawlessly. No
overheating, no problemo. I try it in the Pc however, and it burns up
like fire. It doesn't matter if the fan is plugged into it or not So
I start looking at the differences between the working (breadboard)
and nonworking (PC) states. First I notice that with my little
adapter, the two grounding rails (black wires) are tied together, but
not in the PC. So I bridge them together. Breadboard mode still
works, but Pc doesn't. So then I think, "with the B.B, theres only
one ground, while the PC has two. So I remove a pin from the molex,
same deal. So I give up for a while and watch some sopranos. A
little later I try it in the pc again. It works. It normally gets
hot in less than a minute, but this time it didn't. I leave it
plugged in and keep checking it. Five minutes go by, then ten. A few
hours later, its a little warm, but not hot. Its been plugged in for
over eight hours and its still cool. I don't know why.


Before I tried it again, I messed with the wires in the PC, testing
the voltages in the cables. I don't have time to go into detail, but
it seems as if one of the fans were plugged in upside-down,
effectively swapping the +5 and +12 rails. Not good. I'm going to
monitor it for a few days, and maybe add a feature or two. But this
may be the big 'Problem Solved', and I sure hope it is.