What is the difference between an LM78L05 and a L78L05

[Luke51411]

I don't know who made them.  There from Tayda.  They have L78L05  CE 144   and some wierd looking symbol in the upper left corner.

The only one Tayda lists is the ST micro part. That goes wit the data sheet that Matt linked to above. You can't always be sure with Tayda because they see what they can get at the time, but it likely is the ST part.

I read the two data sheets as having the same pinout. They both have confusing figure captions, the TI sheet has the diagram way offset from the caption and it looks like it goes with the caption above but it goes with the one below.

From what I read, the two figures for the TO-92 package are from the bottom with the output pin to the left when the flat face of the regulator is up. I think they are the same. Most of the pinouts for these are the same, so this is consistent with that. There are some weird ones though.

What I do sometimes is pop them in a breadboard once I'm pretty sure of pinout and put 9v to the in and check the out with my meter to make sure it's putting out 5v. I haven't messed any up this way but I've been correct with the pinout haha. It's just a little extra reassurance. And if you do get it wrong, at least you don't have to worry about removing it from the board.

[bigdaddymrx]

Here is what I got. I hooked up a 9v source to one of my L78L05 and with the flat side facing you, the pin on the right I used for 9V+ in and the center pin as 9V- and I got a reading of 4.81v for the left pin.  Does this sound correct?  Could someone please test a LM78L05(I don't have one) and let me know if you get the same thing for the same pin configuration?

[Luke51411]

That's about what I've gotten from the tayda ones. I think ideally it should be right at 5 but I've used them with no problem.

[RobA]

Here is what I got. I hooked up a 9v source to one of my L78L05 and with the flat side facing you, the pin on the right I used for 9V+ in and the center pin as 9V- and I got a reading of 4.81v for the left pin.  Does this sound correct?  Could someone please test a LM78L05(I don't have one) and let me know if you get the same thing for the same pin configuration?

That pinout is consistent with the LM78L05 spec sheet. The voltage is a bit on the low side, but well within spec for the ST part which states (4.6V to 5.4V). It does fall within the spec'd range of the LM78l05 too (4.8V to 5.2V).  I take it that this is without the input and output cap in place too. The voltage may go up a bit with the caps in place and a load to drive.

The important points now are that you can compare against the layout for your project and see if the pinout matches what your project expects. You can also check that the voltage you get will be OK for your other parts. The high limit voltage of the the ST part is a bit high at 5.4V or 5.5V. The LM part has a tighter limit of 5.25V. If you were actually sitting at 5.4V, that could be a problem for some 5V parts. I really doubt if regulator is going to go up that much when it is in the final circuit, but it's worth checking the output voltage in-circuit and the spec sheets of any 5V parts in the project.

[bigdaddymrx]

This is racking my brain. I'm short 2 damn parts for this build. The J112 and the LM78L05.  I was hoping I was only short one.

[RobA]

The regulator you have should be fine.

What project is this for? If you have other JFET's available, they can often be substituted in with no problems.

[bigdaddymrx]

The laserwolf.  It will be my second build ever (my first being the Chunk Chunk).  Like I said in an older post, I'm going into this hobby 2 fistin' and swinging!!!

[RobA]

Yikes! That's a beast of a build to go after as a second build.

I haven't built a Laserwolf yet. I just checked the layout for the PCB and your regulator looks fine. It's for getting the 5V for the PT2399 and the PT2399 can handle up to 5.5V fine. The absolute max on the PT2399 is actually 6.5V. So your regulator is well within the limits for this build.

I'm looking at the J112 now to see if I can figure out if it's sub-able. Of course, Brian can answer that question better.

[bigdaddymrx]

Would I still orient the L78L05 on the pcb the same way the LM78L05 would go?

[RobA]

Would I still orient the L78L05 on the pcb the same way the LM78L05 would go?

Yeah. If you look at the schematic, the output pin of the regulator hooks to the +pin of C29 and pin 1 of the PT2399. Then you look to the layout with the traces on it. With the regulator rotated 180° to what you had on your breadboard, that puts the right hand pin being the output. If I recall correctly, that's matches what you had.

The best way to handle this situation is to socket the PT2399 and power the board up without the PT2399 in place, then you can measure the voltage at pin 1 of the socket before you put the PT2399 in there. You should socket the PT2399 anyway because some of them are really noisy and you end up needing to change them out for a new one anyway.

The J112 looks to just drive the phaser LFO indicator LED. You could build the circuit and socket that transistor and try different JFET's in there. It looks to me like the phaser would work fine without the J112 in there at all. You just wouldn't have the LED rate indicator until you got one in there that worked.

[mgwhit]

Holy crap!  I just remembered working on a prototype PCB from jimmybjj a few years ago where i "discovered" that the proper voltage regulator orientation was backwards to his silkscreen.  He was 100% sure that his other board worked with the regulator oriented according to the silkscreen, but couldn't check because he had already lent it out.  Can you see where this is going?

Yeah, I just checked.  His build parts list specified LM78L05.  All my parts orders from around that period of time were L78L05s.  I owe him an apology!

[Never mind.  I was misreading the TI datasheet.]

[RobA]

Holy crap!  I just remembered working on a prototype PCB from jimmybjj a few years ago where i "discovered" that the proper voltage regulator orientation was backwards to his silkscreen.  He was 100% sure that his other board worked with the regulator oriented according to the silkscreen, but couldn't check because he had already lent it out.  Can you see where this is going?

Yeah, I just checked.  His build parts list specified LM78L05.  All my parts orders from around that period of time were L78L05s.  I owe him an apology!

I'm still seeing the pinouts of the two as being the same. Here's the two spec sheets from the parts at Mouser,
LM78L05, http://www.mouser.com/ds/2/149/LM78L05A-195676.pdf
L78L05, http://www.st.com/web/en/resource/technical/document/datasheet/CD00000446.pdf

[mgwhit]

I'm still seeing the pinouts of the two as being the same. Here's the two spec sheets from the parts at Mouser,
LM78L05, http://www.mouser.com/ds/2/149/LM78L05A-195676.pdf
L78L05, http://www.st.com/web/en/resource/technical/document/datasheet/CD00000446.pdf

Sorry.  I was misreading one of the datasheets.

[RobA]

The first LM78L05 data sheet linked earlier in the conversation is completely confusing and the L78L05 figure caption is also not as clear as it would be if they just put the view right by each of the  diagrams. I really don't get why those are done they way they are. At least the new TI doc is clear and has a good depiction of the part now. I'm guessing they went to the 3D diagram because they've had complaints about the old data sheet.

Anyway, I'm just trying to be sure that I'm giving the right advice that these two should have the same pinout.