Is this okay?

[rutabaga bob]

Hey y'all!  A quick question regarding voltage regulators like 7809s: is there any detrimental issue from anchoring it to the enclosure - basically using the enclosure as a heat sink?  Thanks!

[statzern]

The tab is almost always "hot" in voltage regulators and most TO-220 packages. It is OK to use the enclosure as a heat sink but you need to isolate the tab with something like a sil-pad or mica insulator and insulating washer, otherwise it will short to ground and you will burn up your regulator and possibly other things like your power supply. See here: https://www.amazon.com/Insulator-Mounting-TO220-Rubberized-Silicone/dp/B00KR4KFH2

[rutabaga bob]

I don't think that's right...the center leg and back plate on a 7809 are ground, IIRC.  I will have to check the datasheet.

[vigilante397]

It's absolutely fine. If you look at the LM7809 datasheet you'll see that the tab is grounded. Datasheets aside, I do this all the time, especially with 6V regulators in tube pedals.

[bloxstompboxes]

If they all have the same pinout, a TO-220 package 7809 regulator has a center pin and the tab as gnd. Check the PDF:

https://static1.squarespace.com/static/5416a926e4b09de8832655bc/t/54427037e4b03de3b67b895a/1413640247188/lm7809.pdf

[rutabaga bob]

All right!  Thanks for the responses!  I'm getting ready to do a Lonewolf with a 6AK5...those dad-burn regulators can put out some heat!

[Ice-9]

Yeah the 7809 220 package has the ground connected to the body of the regulator so you can bolt the regulator directly to a ground chassis/enclosure, it is still good practice to use the mica or silicone wafer insulator as these can also provide thermal contact.

[GGBB]

If the regulator is PCB mounted as well, you will probably want to also secure the PCB to the enclosure (via standoffs of course), otherwise you are asking for trouble with the PCB moving around slightly and stressing the regulator joints. Overall, disassembly could also prove to be a pain should you need to repair it.

[Fancy Lime]

Whole other question: Do you actually need to connect it to a heat sink? How much voltage are you going to feed this thing (potentially)?

Andy

[vigilante397]

It depends. I have a dual-tube overdrive with regulated heaters, so it's pulling 600mA at 6.3V. When I use a 9V supply I'm only dumping a couple volts into heat, so I can get by without a heatsink. But when I use a 12V supply I'm dumping a lot more heat and the regulator will fry without a heatsink.

So it depends on how much current you pull, and how many vokts are dumping to heat (supply voltage - regulator output voltage).

[ElectricDruid]

Just to say that Statzern's advice is still sound. In this case you're fine, and that's handy. But if you'd been talking about a negative regulator, the tab is connected to the input:

http://www.hep.upenn.edu/SNO/daq/parts/lm7915.pdf

I've also come across some negative regulators that don't share the usual pinout, so the rule remains "Check the datasheet!", same as it ever was.

Tom