Did i kill my 7805?

[Marks256]

I have a neat little power supply that i made up. Here is the link to the schematics; **broken link removed**

I have a 9Vdc @ 500mA power supply running into it. I just turned it on, and my z80 circuit booted, i then went to turn the manual clock on, and everything just, shut off? I immediately turned off the power switch. Now, when i try to turn it on, the 7805 gets REALLY hot REALLY fast. I did have a heat sink on it, too. What is the deal? I am guessing i blew it out.

 

[eblc1388]

Test the 7805 alone without the Z80 connected.

A good 7805 will gives close to 5V at its output and remains cold without load.

 

[RadioRon]

7805 is hard to blow out due to load problems because it has a thermal limiter built in. If it is getting hot with a load attached, there is probably a bad load, like a short circuit.

 

[Marks256]

Oh my God! I feal soooo embarrassed! I found a short circuit! :embarrassed: My bad. One of my CAPS were shorting on one of my resistors. Sorry for starting a full thread about this? Oh well, i am going to put a fan on the heat sink tomorrow.

 

[Dr.EM]

Once you have eliminated the short, you probably won't need the fan? What is the proper current drain of the circuit, got to keep it under 1A for the 7805.

 

[Nigel Goodwin]

Once you have eliminated the short, you probably won't need the fan? What is the proper current drain of the circuit, got to keep it under 1A for the 7805.

And WELL under 1A if you don't want to make toast on the 7805!

 

[JimB]

I have a 9Vdc @ 500mA power supply running into it.

Less than 500mA would be better!

JimB

 

[Marks256]

No. The thing gets very hot as it is. I know i am sucking A LOT of power from this baby. Soon, i am going to pull the power supply out of an old Apple 2e. I have the connector all soldered together, but i am just to lazy to pop the thing out.

I rigged up a nice i686 fan onto it. I just have to figure out how to mount it? I am thinking Twist-Ties, or maybe cable ties? I don't know right now. I think i will go get that power supply!

 

[AllVol]

For what it is worth, I recently built a little 7805-regulated psu that I have successfully used for several projects. The attached shows it powering a two-digit counter that has been in continuous operation for a couple of months.

I am using a Hewett-Packard wall-wart that is labeled 9 vdc @1000 mA.
I have not had any heat problems. As can be seen, I do not have to use a heat sink.

AllVol

 

[Marks256]

Then why on earth does mine get so HOT? I have literally burned my finger on the thing!

 

[AllVol]

I dunnough.... I have goofed up a few times and got things backwards. They got hot in a hurry, sometimes even to the point of extinction. Carefully check everything. Sometimes an error can be so obvious it looks correct.

Allvol

 

[Nigel Goodwin]

Then why on earth does mine get so HOT? I have literally burned my finger on the thing!

For a start, do you have capacitors on the input and output, with short leads as close as possible to the 7805? - if not it's probably oscillating?.

Assuming you do, then measure the current it's taking from the supply, and also measure the input voltage (don't beleive the spec on the PSU).

 

[Marks256]

Yes, i have got the filter caps on the input, and on the output. I don't have anything to test it with, but the fan keeps it nice and cool now.

 

[Nigel Goodwin]

Yes, i have got the filter caps on the input, and on the output. I don't have anything to test it with, but the fan keeps it nice and cool now.

A Z80 is a fairly hungry chip - I would still suggest you measure the current though. If you haven't got a multimeter I suggest you go out and buy one!, you can't do anything without one, you've got a breadboard - you should have bought a meter first!.

 

[Marks256]

I now, but i only have $5us right now. I used to have one, but i blew it out(long story). I know that the Z80 is a HUGE power hog. I am just going to connect a new power supply to it.

 

[Nigel Goodwin]

I now, but i only have $5us right now. I used to have one, but i blew it out(long story). I know that the Z80 is a HUGE power hog. I am just going to connect a new power supply to it.

Did I mention that a PIC16F628 running at the same 4MHz as the Z80 will absolutely wipe the floor with the Z80 design, and only consume mA's (or even uA's), oh and only cost a tiny amount as well!

 

[Marks256]

Ok. For the LAST TIME, i do NOT want to use a PIC. Yes, they are great, but i don't have a use for ONE! I just want to see if i can build a computer using a CPU and the other necessities. NOT A PIC!

Seriously, what is so hard to understand about that? Hmm? I just don't want to! Ok? Now, please stop harassing me with the god-forsaken word "PIC"!

 

[Andy1845c]

*****Off Topic*****

Mark - I like your sig. I love those old CW McCall Songs lol

BTW, where in MN are you?

 

[Marks256]

BTW, where in MN are you?

I live between Spring Valley, Ostrander, Grand Meadow, and Le Roy. In other words, Southeastern Minnesota. Or, about 25 miles south of Rochester. Not sure how far from Austin, though. What about you?

Mark - I like your sig. I love those old CW McCall Songs lol

Yeah, Convoy is a cool song. I am actually starting to make a cartoon music video of it. I have some cool software that allows you to make animations. Very neat. It is called "Anim8tor". A simple google of that will lead you to their homepage.

 

[Andy1845c]

I live between Spring Valley, Ostrander, Grand Meadow, and Le Roy. In other words, Southeastern Minnesota. Or, about 25 miles south of Rochester. Not sure how far from Austin, though. What about you?

Pretty part of the state I hauled a dozer out of that area a few years ago.
I live in North Mankato.

Yeah, Convoy is a cool song. I am actually starting to make a cartoon music video of it. I have some cool software that allows you to make animations. Very neat. It is called "Anim8tor". A simple google of that will lead you to their homepage.

Thats cool. Have you heard any of CW other songs? Hes got quite a few that are equally as colorful and comic