# NE555P IC burns out

#### DrCowiber

Joined Jul 15, 2021
16
I am using this circuit- VCO 555 Circuit
when I plug a 9 volt battery in its fine, but when I plug a 9 Volt DC converter, at 850mA the IC gets hot and burns out.
This doesnt make sense to me as the way I understand it parts draw only the amperage they need, but here it seems to be the amperage burning my IC out. I am asking why this is happening, and if there is a way to avoid it?

what im thinking is that the diode might be pulling amperage and is overheating the IC, but I dont really know.

Note: I am using a different diode, it says RI03, MIC on the side of it, and it looks like it would be slightly bigger than the 1N4007 diode.

#### dl324

Joined Mar 30, 2015
13,078
Welcome to AAC!

Circuit in question:

Since you don't have problems with a battery, it has to be the power supply. Is the output actually a clean 9V?

#### DrCowiber

Joined Jul 15, 2021
16
Welcome to AAC!

Circuit in question:
View attachment 244330
Since you don't have problems with a battery, it has to be the power supply. Is the output actually a clean 9V?
I am not totally sure how to check this.. I am fairly new to this kind of thing.
I plugged a 9 Volt battery and the Converter into my Oscilloscope. On the converter the waves were much larger, although this was only really noticeable on the highest "zooms".

I also put these through my multimeter. the Battery was at 8.45 (I doubt if thats all that useful) and on my converter it was at 13 volts?
I see the problem now, but how does that happen? Its an old casio converter from china, so im guessing cheap parts or age affecting it.

#### MrChips

Joined Oct 2, 2009
24,134
A 9V adapter is spec'd to give the rated output under full load.
With no load the output could be much higher. This still does not explain the overheating problem.
NE555P can operate with voltages up to 16V.

Disconnect the load at pin-3 and test again.

#### DrCowiber

Joined Jul 15, 2021
16
A 9V adapter is spec'd to give the rated output under full load.
With no load the output could be much higher. This still does not explain the overheating problem.
NE555P can operate with voltages up to 16V.

Disconnect the load at pin-3 and test again.
ah im afraid I burnt out both of my NE555P's, so I cant do much until I get more

#### MrChips

Joined Oct 2, 2009
24,134
Maybe you got counterfeits.

NE555P are inexpensive. $0.50 each. Buy them in quantity from a reputable supplier (not your popular on-line retailer). Thread Starter #### DrCowiber Joined Jul 15, 2021 16 Maybe you got counterfeits. NE555P are inexpensive.$0.50 each. Buy them in quantity from a reputable supplier (not your popular on-line retailer).
I did get them from a local place, but I can rarely get there as my dad is at work while they are open, So I cant be driven. So the only good option I have is to order them off digikey.

Last edited:

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,063
Bypass cap missing. See datasheet.

#### dl324

Joined Mar 30, 2015
13,078
I plugged a 9 Volt battery and the Converter into my Oscilloscope. On the converter the waves were much larger, although this was only really noticeable on the highest "zooms".
Post a picture of the scope waveform. If you don't have on-screen indicators for vertical sensitivity, tell us what it is. Don't know what "highest zooms" means.

#### click_here

Joined Sep 22, 2020
374
It's possible that you have the +\- back the front for the DC power supply input.

It might be worth doing a sanity check with a multimeter

#### DickCappels

Joined Aug 21, 2008
7,687
Is it possible that the "7555" shown in the schematic is a CMOS version with a lower rating than the NE5555?

#### MrChips

Joined Oct 2, 2009
24,134
Reversed polarity on the power adapter would certainly kill the chip. This is too obvious an error that it didn’t even cross my mind.

I would have assumed that you verified the polarity even before connecting it. Always double check the polarity from a DC wall adapter before using for the first time.

#### DrCowiber

Joined Jul 15, 2021
16
Post a picture of the scope waveform. If you don't have on-screen indicators for vertical sensitivity, tell us what it is. Don't know what "highest zooms" means.
sorry about that, I didnt know what the vertical sensitivity knob was called, ive had this for about a week.

First one is the battery, the second one is the adapter.

#### DrCowiber

Joined Jul 15, 2021
16
It's possible that you have the +\- back the front for the DC power supply input.

It might be worth doing a sanity check with a multimeter
Reversed polarity on the power adapter would certainly kill the chip. This is too obvious an error that it didn’t even cross my mind.

I would have assumed that you verified the polarity even before connecting it. Always double check the polarity from a DC wall adapter before using for the first time.
I do remember doing a check with a multimeter and a polar led light. I will not cross out that this could have burnt them out as I did not know reverse polarity would kill the chip, so I could not have been careful as I should have been.

#### Audioguru again

Joined Oct 21, 2019
3,499
You have the vertical sensitivity on the 'scope set to the maximum which is 5mV (0.005V) per division. It shows only background noise.
The output of a 555 with no load and powered from 9V is about 7.8V from its maximum to its minimum. Then set the 'scope to show 1V or 2V per division.

#### eetech00

Joined Jun 8, 2013
2,565
I am using this circuit- VCO 555 Circuit
when I plug a 9 volt battery in its fine, but when I plug a 9 Volt DC converter, at 850mA the IC gets hot and burns out.
This doesnt make sense to me as the way I understand it parts draw only the amperage they need, but here it seems to be the amperage burning my IC out. I am asking why this is happening, and if there is a way to avoid it?

what im thinking is that the diode might be pulling amperage and is overheating the IC, but I dont really know.

Note: I am using a different diode, it says RI03, MIC on the side of it, and it looks like it would be slightly bigger than the 1N4007 diode.

#### ericgibbs

Joined Jan 29, 2010
13,579
hi DrC,
Can we also confirm the the AC/DC select switch of the Scope is set to DC, lets check the DC level.
E

#### dl324

Joined Mar 30, 2015
13,078
I didnt know what the vertical sensitivity knob was called
In addition to vertical sensitivity, we also need to know where 0V is and what coupling is set to.

#### DrCowiber

Joined Jul 15, 2021
16
hi DrC,
Can we also confirm the the AC/DC select switch of the Scope is set to DC, lets check the DC level.
E
when I switch my channel to DC on my scope, the wave isnt always visible on the screen, not matter how I adjust the position.
I was just messing around to see if im doing something wrong, and im noticing that when I turn up the vertical sensitivity that the line goes off screen. Other than that, it looks like a straight line, on both the battery and adapter.
Edit: I can only turn it up so far before it goes off screen, but thats is pretty high in. and I have the mode set to TV-H, because the wave is the most easily visible on there.