78DL05AP problem

[mdanh2002]

Hi, I found a bunch of 78DL05AP voltage regulators in my junk box. I assume it has the same pinout as LM7805. However. when I applied 9V to it, all I get is 8.9V output. This is the same for all these chips. Can I assume that those chips are faulty? It's hard to believe all of them are faulty!

 

[ericgibbs]

hi,
Look at this d/s for pins.

 

[House0Fwax]

I assume it has the same pinout as LM7805

Don't assume, check the datasheet. I had a quick look at the Toshiba sheet, and it claims the legs are numbered left to right 1,3,2. Which I thought was strange for a start.

 

[mdanh2002]

Thanks eric, that's the datasheet I am using too. The part suffix is AF but I believe the pin layout should be the same. My 78DL05AP has the same packaging as other 7805s I am using. So I believe mine are faulty. What possibly could have caused all of them (~20) to fail?

 

[ericgibbs]

Thanks eric, that's the datasheet I am using too. The part suffix is AF but I believe the pin layout should be the same. My 78DL05AP has the same packaging as other 7805s I am using. So I believe mine are faulty. What possibly could have caused all of them (~20) to fail?

hi,
I dont make the pin out the same.???

 

[mdanh2002]

Don't assume, check the datasheet. I had a quick look at the Toshiba sheet, and it claims the legs are numbered left to right 1,3,2. Which I thought was strange for a start.

Hi, I noticed that too. But I believe it's just the numbering: 1: Input, 2: Output, 3: Common and the order is 1,3,2 so it should not be so strange. I tried various combinations just for the benefits of doubt and could not get the correct output

 

[ericgibbs]

Hi, I noticed that too. But I believe it's just the numbering: 1: Input, 2: Output, 3: Common and the order is 1,3,2 so it should be the same as a normal 7805.

hi,
Try one as per that image I have just posted,, I hope you have not damaged any with a reverse voltage.

 

[mdanh2002]

Thanks, I will try again

 

[mdanh2002]

Hi Eric,

I just tried with your suggested pinout (which I believe I have tried before), and all of them produced 8.9V! I don't think a 7805 can be easily damaged by reverse voltage - I tried applying input voltage to wrong pins with a 'normal' 7805 and it still seemed to function normally once the correct voltage is applied. Not to mention that previously I only tried a few random pieces among them, and not all of the 78DL05APs. So my 78DL05APs are somehow faulty - unbelievable but unfortunately seemed true.

What could have been the reason?

 

[ericgibbs]

Hi Eric,

I just tried with your suggested pinout (which I believe I have tried before), and all of them produced 8.9V! I don't think a 7805 can be easily damaged by reverse voltage - I tried applying input voltage to wrong pins with a 'normal' 7805 and it still seemed to function normally once the correct voltage is applied. Not to mention that previously I only tried a few random pieces among them, and not all of the 78DL05APs. So my 78DL05APs are somehow faulty - unbelievable but unfortunately seemed true.

What could have been the reason?

hi,
It depends where you got them from, they could be manufacturing rejects.??

 

[mdanh2002]

hi,
It depends where you got them from, they could be manufacturing rejects.??

I remember I got it from a electronics hobbyist who wanted to give away some of his components for free. Some 2 years ago. Also remember that I did test a few random pieces among them when I first got them, and they appeared to be working well. Very strange...

 

[ronsii]

Hi, I found a bunch of 78DL05AP voltage regulators in my junk box. I assume it has the same pinout as LM7805. However. when I applied 9V to it, all I get is 8.9V output. This is the same for all these chips. Can I assume that those chips are faulty? It's hard to believe all of them are faulty!

Hi mdanh, I don't know if you ever found and answer to this problem but I thought I would post in case others see this and are looking for a solution.

I have some of the 78DL05ap's made by toshiba and if you do not put a 100 micro farad cap on the output they will also not give you 5 volts instead they output just about the input voltage, I was told to use low ESR caps not sure if you have to as I have only used the low ESR caps.

 

[simonbramble]

I have some of the 78DL05ap's made by toshiba and if you do not put a 100 micro farad cap on the output they will also not give you 5 volts instead they output just about the input voltage

Beware - you need input and output decoupling caps close to the pins. I have used the 7805 type regs without decoupling caps and the parts oscillate. Electrolytics should be OK.

 

[KeepItSimpleStupid]

Check minimum loads.