I don't think they should be so expensive... I'm just guessing they don't sell many of them. I know Digikey is always a little more expensive, but I love shopping there because you can find what you want quickly, and shipping is fast. But $37 for that regulator blew me away! The LM323's are great but they cost $37 at Digikey too!?? That's too much!
I'm checking the LM350K, also $37. The LM338K are costing $50??? c'mon, that's crazy.
John, you're right about the 7805C (1.5A)... on the 8080 board, they run hot. but no harm seems to come from it.
But I love the big TO-3's. There's something you can use a wrench to bolt it onto a heat sink! My first 5V power supply I built back in 1979 used a 10Amp transformer and a 78H05 (or 78P05) I forget which one is the 5Amp version? I still have that regulator here... somewhere... I think...Yes, here it is.. found it. It's got a few rust specs on it... UA78H05SC from Fairchild, date code 7837.
I know it's not that old... but it's just funny to think that I've owned and used it since it was new. I wonder if it's worth $50? LoL.
Regards,
Josh
From: mon...@vitasoft.org
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:6440] Discussion About Filter Capacitors
Date: Tue, 24 Feb 2015 15:55:22 -0800
Bob there were some treads about the TO-3 5V regulators about a year ago here. In the past the used market was flooded with” Chinese knockoff’s”. The voltages were all over the map. I always test them these days before inserting into a board. Within about 5% of V into a flash lamp bulb being my cutoff. Jameco sells the LM323K’s (5V,3A) for$ 4.75, #23667. They sell the 7895K’s (5V 1A) for $2.49. I actually like the 78H05’s I get from Anchor Electronics (www.anchor-electronics.com ), $2.95. Never had a problem with them.
The reason I use these (old) TO-3 regulators is they seem to have much better heat dissipation, particular when you go above 1A in comparison to the TO-220’s where at 1.5A’s you can burn your finger!
Tom Lafleur was kind enough to make me up a small circuit board using a LM22677 modern day switching 5V regulator – thanks Tom. It contains a few components besides the regulator but runs almost cold. I intend to try and incorporate a circuit like this on later high ampage S100 boards, but for ease of use, it’s hard to beat those old TO-3’s.
John
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Bob Bell
Sent: Tuesday, February 24, 2015 2:58 PM
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:6439] Discussion About Filter Capacitors
Hey, I have the 1984 version of the IC Master.
There’s absolutely no memory of where I got the LM309K. Maybe it was bad from the start.
That shorted LM309K was the only one I ever had. I never knew it would be that expensive!
And I don’t know of any advantage of it over the 7805.
There’s also an LM323K – I know that’s expensive. It’s rated for 3 Amps.
Bob Bell
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Crusty OMO
Sent: Monday, February 23, 2015 11:25 PM
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:6431] Discussion About Filter Capacitors
Hi Bob,
That's about the only one I ever heard of... and might be because of it's early age!?
Speaking of rarities... I once found a 1N914 diode that was marked wrong! I kept it for a year then tossed it out... silly me.
I'm sure the rarity of it would make that diode worth a whole dollar on the ebay market! LoL
So, what's the deal between 309's and 7805's? I'm thinking it's a manufacturer part numbering scheme... worth a minute to research in my IC MASTER 1982.
Let's see... makers of the 309 chip are:
Fairchild
Motorola
National
Silicon G
Siliconix
Makers of 7805
Fairchild
Motorola
National
NEC
SGS
Silicon G
TI
I suppose it doesn't mean much, if Fairchild dropped the 309 and replaced it with the 7805... I just wouldn't see the dates...
I'm looking up Digikey, they sell LM309K's (for $37.20 ouch!) from TI.
I guess the next logical place to check the differences would be in the data sheet... but it's too late at night now to do this... and my curiosity is going.
Cheers,
Josh
From: bbel...@gmail.com
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:6426] Discussion About Filter Capacitors
Date: Mon, 23 Feb 2015 18:44:37 -0500
Yes, that would be the situation for a complete board. However, I was incredibly lucky when I ran across the one shorted regulator I have ever seen. It was an old LM309K (precursor to the 78xx series, I think) in a TO-3 package. I was using it to build a bench power supply for prototyping. So, of course, after building it, I measured the output with a meter and found it to be the same as the input. What more is there to say? I replaced the regulator and moved on, never to see one shorted again. I guess I should have saved it for posterity!
Bob Bell
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Crusty OMO
Sent: Monday, February 23, 2015 12:36 PM
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:6421] Discussion About Filter Capacitors
I doubt you would forget a shorted regulator... that would likely blow every chip on the board, or perhaps if there are many chips, the quick rise in current would take down the power supply? I have repaired boards that were hit by lightning... I recall needing to change nearly every chip... with only a few original chips working, I changed those too, just in case there was any kind of hidden damage. In hind sight, I think those type of boards should be scrapped.
> Date: Mon, 23 Feb 2015 06:30:52 -0800
> From: gregor...@gmail.com
> To: n8vem...@googlegroups.com
> Subject: RE: [N8VEM-S100:6419] Discussion About Filter Capacitors
>
> I don't remember a shorted 7805, but I could have missed one through the years.
> Majority had no voltage (+5V) output, failed open.
>
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