LM338K Availability

[Electromotive]

Hi:
I am building two regulated DC power supplies for my O-Scale (2 Rail) layout per the LM138/LM338 data sheet. I have built two 1A DC supplies but they are a little anemic for this larger scale system.

I have all the parts and components but am afraid of the e-bay LM338K's. One of the 2 is definitely a problem. I would like to purchase a minimum of 5 quantity.

It is a 0-18VDC power supply using a 4 Amp 24V transformer. I would prefer the T0-3 K Steel package but see that most of the reputable US firms like Mouser, Digikey and Newark are either $50 each or unavailable.
I need the 1.2V lower end limit, as 4V may already initiate the train starting.

Also, I am not sure how to calculate the heat dissipation. My Heat sink is 2" x 3" x 4".

 

[Electromotive]

I am so afraid of the various potentially knock-off manufacturers of the LM338K. I find them from $1.00 to $60 and that is bulk rate.
Here are some of the more reasonable P/N's:
SH1035
Sh12AB (Backwards) S
H4D0452A
H:0512
H4D1602A
H1027 S
9442 Philippines
Jameco 23835
ST Microelectronics
Can anyone advise what a reasonable price is for an LM338K? And a possible source?

Thanks... Tom

 

[Ylli]

If it were me, I'd go here: https://www.newegg.com/Product/Prod...IC-_-9SIA6RP36W3643&ignorebbr=1&source=region

 

[Electromotive]

Hi Ylli:

Thank you for your kind response.
Working with these older and often discontinued items is a little frustrating.

Can you advise why you feel the New Egg vendor is the way to go?

The LM338K on this web sight has the same SH12AB P/N as many on e-bay. The part is coming from Israel and the vendor ALEXNLD has a miserable track record of deliveries (>>1 month) and only rates a positive of 54% out of 892 reviews. That is a low rating and the number of reviews is rather low for an active electronics part vendor. On the other hand, New Egg puts up with him/her.

While I thank you for your response, I don't feel real comfortable with this vendor. Maybe someone here has personal dealings with the LM338K.

Thanks... Tom

 

[Ylli]

Always had acceptable service from Newegg. Alternately, you could always go with an LM317 and an external pass transistor.

 

[Electromotive]

Hi Again:
After reviewing all options on LM338K non-availability or cheap knock-off's everyone is advising against due to inferior product, I have ordered LM338T's from Newark. Slightly different package but should work. And they are made by Texas Instruments at less than $2.00 each.

Thanks to all for the help in this.

Tom