(Topic ID: 338811)

Replacement for the LM338K wanted

By Inkochnito

1 year ago


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    There are 72 posts in this topic. You are on page 1 of 2.
    #1 1 year ago

    I've been looking all over the internet, but can't seem to locate a trustworthy supplier for the LM338K.
    The LM338K is no longer in production as far as I know.
    Spare parts are getting harder to find.
    Ebay, Ali express, they are full of fake parts.
    Easy to spot a fake because of the big blue isolator around each leg.

    Anyone know a good source to buy from?
    Or an alternative way or part?

    Peter

    LM338K_fake (resized).jpgLM338K_fake (resized).jpg

    #2 1 year ago

    I suspect you need the part for an 80B power supply.
    I think I still have a few genuine parts I bought from GPE ages ago but being on the wrong side of the Atlantic makes shipping a bit tough.

    I've come to the conclusion that it's just better to buy a new power supply that is based on a different regulator. They aren't that more expensive than the cost of a known genuine LM338.
    --
    Chris Hibler - CARGPB #31
    http://www.ChrisHiblerPinball.com/Contact
    https://www.youtube.com/c/ChrisHiblerPinball
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

    #3 1 year ago

    ebay.com link: itm

    I think these are good.

    #4 1 year ago

    But no guarantees

    #5 1 year ago

    Some of The fakes are printed horizontally inline with the holes. I believe the originals are printed vertically between the holes

    #6 1 year ago

    Real ones are effectively NLA, unless you find a small stash that someone has squirreled away.

    GPE was basically the one source I trusted for hard-to-find and often faked parts. G-P-E may be able to offer some tips on sorting real from fake, but the simple and unfortunate fact is that the component has been discontinued and legitimate sources have dried up. I imagine we're going to be seeing more and more of this in coming years.

    If you are trying to repair an 80B power supply, an aftermarket board it is almost the same price as a genuine LM338K now:

    https://nvram.weebly.com/gtb-80b---sys3-5v-ps.html

    #8 1 year ago

    The LM338K is also used on the Stern Whitestar boards.
    That is where I need it for.
    I did find some on Ebay in Italy for 18 euro plus shipping, but that source will dry up sometime.

    I suppose one can tie in an external 5V-5A (or more) power supply.
    It won't be pretty, but it can work.
    There are 5V-15A videogame power supplies for less than the cost of a LM338K.
    Simply tie in the 5V and ground to the board and be done with it.
    I suppose one can also use the replacement System-80B power supply mentioned above.
    I was hoping for a more cleaner mod.
    Are there no other parts to use for a step-down voltage regulator?

    LM338K_schematic_use (resized).jpgLM338K_schematic_use (resized).jpg

    #9 1 year ago

    Would this Buck Step-down regulator be an option?
    ebay.com link: itm

    10
    #10 1 year ago
    Quoted from Inkochnito:

    Would this Buck Step-down regulator be an option?
    ebay.com link: itm

    Yes, it works ...
    Edit: picture is from Bally pinball, if you look for a replacement for Gottlieb 80B take a look on my website
    https://lisy.dev/psy80b.html

    pasted_image (resized).pngpasted_image (resized).png

    #11 1 year ago

    https://www.amazon.com/gp/product/B091343QH2/ref=ox_sc_act_title_1

    $13.85 for 10 of them; I'm sure they are straight from China and they will either work or not, but at that price its worth trying IMO.

    #12 1 year ago

    Those are fakes.

    #13 1 year ago
    Quoted from Pin_Guy:

    amazon.com link »
    $13.85 for 10 of them; I'm sure they are straight from China and they will either work or not, but at that price its worth trying IMO.

    It looks indeed that those LM338's are also fake.

    #14 1 year ago
    Screenshot_20230625-090031 (resized).pngScreenshot_20230625-090031 (resized).png
    #15 1 year ago
    Quoted from jj44114:

    Those are fakes.

    Quoted from Inkochnito:

    It looks indeed that those LM338's are also fake.

    as I said ...

    Quoted from Pin_Guy:

    I'm sure they are straight from China and they will either work or not, but at that price its worth trying IMO.

    #16 1 year ago

    Perhaps the 5amp LM1084 and a heat sink with a little mounting creativity?

    #17 1 year ago

    Here is another proof image that they are fake....
    How in Gods name do they expect 5 amps to go through those hear thin wires?
    Even a 5 amp fuse has a thicker wire.
    The cap came lose when I was trying to saw the top off.

    LM338K_fake_proof-1 (resized).jpgLM338K_fake_proof-1 (resized).jpg
    #18 1 year ago

    Cool them to near absolute zero and they’d handle 5A without any problem. I’d be curious to mount it to an adequate heatsink, add bypass caps to the input and output and then connect a power supply (9 - 12 v) with at least a 5A rating and then measure the output voltage across a 1 ohm load (25 w resistor for example). I’ll bet, if it doesn’t fail immediately, the output will be near zero

    #19 1 year ago

    Yeah, but will it blend?

    #20 1 year ago

    I had an entire eBay order of regulators, many years ago, test good using diode test. But as soon as it was used in a real application, pulling the necessary current, it failed. At least they were cheap….

    I got what I paid for.

    Chris Hibler - CARGPB #31
    Http://chrishiblerpinball.com/contact
    Thank you for checking out the PinWiki - http://www.PinWiki.com/

    #21 1 year ago

    That’s a great image for the PInWiki.

    Chris Hibler - CARGPB #31
    Http://chrishiblerpinball.com/contact
    Thank you for checking out the PinWiki - http://www.PinWiki.com/

    #22 1 year ago

    It looks like the active part of a TO92 regulator, like the 7805. The LM1084 with a heatsink or any modern 5 volt regulator would be better than the fake.

    #23 1 year ago

    Not sure why everyone is ignoring the NTE replacement. I used only one so far and it is great replacement. Make sure to get them from authorized resellers.

    #24 1 year ago
    Quoted from PinballManiac40:

    Not sure why everyone is ignoring the NTE replacement. I used only one so far and it is great replacement. Make sure to get them from authorized resellers.

    I did not ignore the NTE935.
    I just like the voltmeter on the Buck step-down board a bit more, sorry.
    It is good to see there is an drop-in part still available, but for how long?
    The NTE935 cost around 30 euro or $25.

    The part is available at Digikey
    https://www.digikey.com/en/products/detail/nte-electronics-inc/NTE935/11655015
    And a bit cheaper at RS-online
    https://us.rs-online.com/product/nte-electronics-inc-/nte935/70215552/
    Not available at Mouser at this moment.

    In Europe it is available at Reichelt
    https://www.reichelt.com/de/de/ldo-regler-einstellbar-1-2--32-v-to-3-nte-935-p217067.html?r=1
    Or at TME
    https://www.tme.eu/nl/details/nte935/spanningsstabilisatoren-instelbaar/nte-electronics/?gclid=CjwKCAjw-vmkBhBMEiwAlrMeF2i_-4DSu2LUdcKqeF3SXUDOBusAJbeUoU7eNrG_Oy2bRQUnei2GxhoCDRkQAvD_BwE&gclsrc=aw.ds

    #25 1 year ago
    Quoted from ChrisHibler:

    That’s a great image for the PInWiki.

    Chris Hibler - CARGPB #31
    Http://chrishiblerpinball.com/contact
    Thank you for checking out the PinWiki - http://www.PinWiki.com/

    I'll send you a copy of the original images per email.

    #26 1 year ago

    Will this one work?
    Looks like a slightly more expensive version with higher temperature tolerances.
    https://www.mouser.com/datasheet/2/389/CD00000548-490721.pdf

    ebay.com link: itm

    #28 1 year ago
    Quoted from Pin_Guy:

    Will this one work?
    Looks like a slightly more expensive version with higher temperature tolerances.
    https://www.mouser.com/datasheet/2/389/CD00000548-490721.pdf
    ebay.com link: itm

    Mouser does not show the LM138 or LM238 when I do a search.

    The Ebay link seems to be the original part, but be aware that you may have to adjust or replace a resistor.
    According to the typical schematic you need to put in a resistor of 240 ohm.

    Also this part is marked as obsolete.

    LM138_LM238_typical_schematic (resized).jpgLM138_LM238_typical_schematic (resized).jpg

    #29 1 year ago

    Looks good.
    Production date looks like it is made in 1989, week 35.
    It might be an original part.

    #30 1 year ago

    The ST parts on ebay - they are shown in packaging that is not provided by ST. I wouldn't trust that one.
    The link to the Linear Tech equivalent provided by mbwalker - those do look to be legitimate.

    #31 1 year ago
    Quoted from Inkochnito:

    According to the typical schematic you need to put in a resistor of 240 ohm.

    Good Catch, you would need to change R115 on the Whitestar board to use that one.

    #32 1 year ago
    Quoted from Markharris2000:

    Perhaps the 5amp LM1084 and a heat sink with a little mounting creativity?

    Would need a very good heat sink. Pretty sure these Gottlieb 80b have the biggest 5v load out of any system except maybe WPC.

    For a switch mode replacement, I'd probably of try to put an efficient buck regulator inside of the foot print of the heat sink, not try and squeeze it into the TO-3 package. Some of the SMPS regulator chips are pretty much jelly bean status now, cheap, and should have better availability from more than a handful of brands in the future.

    On the stern whitestar boards, check the screw mounting on the heat sink. They connect the case through the screw mount and those black anodized heat sinks are not very conductive. When the screw starts to loosen the 5v drops outs. Fixed 3-4 stern games with that same issue just by tightening the screw.

    #34 1 year ago
    Quoted from G-P-E:

    The ST parts on ebay - they are shown in packaging that is not provided by ST.

    G-P-E Curious, was this comment about my e-bay link as ST absolutely made this part in a TO-3 package; just not in the last 10 years.

    #35 1 year ago

    Just curious, would the LM317 be an option? The TO-220 has the output on the mounting tab, just like the LM338.

    #36 1 year ago
    Quoted from Rene368:

    Just curious, would the LM317 be an option? The TO-220 has the output on the mounting tab, just like the LM338.

    The LM317 is only 1.5A. If the OP wants to go down that path, I'd look at a LT1083 series: https://www.analog.com/media/en/technical-documentation/data-sheets/108345fh.pdf

    That was just from a quick google search, didn't look into if that was the best choice or not.

    #37 1 year ago
    Quoted from mbwalker:

    The LM317 is only 1.5A. If the OP wants to go down that path, I'd look at a LT1083 series: https://www.analog.com/media/en/technical-documentation/data-sheets/108345fh.pdf
    That was just from a quick google search, didn't look into if that was the best choice or not.

    The specs for the LT1083 do look good.
    The resistors match.
    Does anyone have any idea about the heat dissipation with the original heat sink?
    Does the LT1083 match the pinout?

    #38 1 year ago
    Quoted from Inkochnito:

    The specs for the LT1083 do look good.
    The resistors match.
    Does anyone have any idea about the heat dissipation with the original heat sink?
    Does the LT1083 match the pinout?

    I'd have to check. Being these are both linear regulators, efficiency will suck regardless, but I can look at the numbers as a sanity check.

    So being linear, whatever the input voltage is, minus the output voltage (x the current) is what will be dissipated. For example. 12V in, 5V out= 7 V across the part. Power is V * I. 7V (across the regulator) and let's use 5A: 7V * 5A = 35 watts as heat. That's a given regardless of the part.

    However, the parts are different and there's a chance that one could be better at getting the heat out of the part vs. the other. That's due to the thermal resistance of the part (which ultimately determines the die temperature). i.e. The die being the 'part' (no case) - it has to remain below a certain temp. See below.

    Sorry, got a little technical there.
    pasted_image (resized).pngpasted_image (resized).png

    #39 1 year ago

    I have no experience with Gottlieb boards so this information is NOT directed at Gottlieb but rather just general information to help with heat dissipation from regulators in general.

    My advice would be to use a switching regulator. Avoid linear regulators unless you intend to contribute significantly to the thermodynamic death of the universe.

    • 96.2C. LINEAR regulator LM350 with 5298 heat sink.0_linear_lm350.jpg0_linear_lm350.jpg
    • 88.3C. LINEAR regulator LM1084 with 5298 heat sink.1_linear_lm1084.jpg1_linear_lm1084.jpg
    • 63.5C. LINEAR regulator LM323K with 500403 style heat sink.2_linear_lm323k.jpg2_linear_lm323k.jpg
    • 46.2C. SWITCHING regulator LM2576 with 6021 style heat sink.3_switching_lm2576.jpg3_switching_lm2576.jpg
    • 32.8C. SWITCHING regulator LM2678 with 6021 style heat sink.4_switching_lm2678.jpg4_switching_lm2678.jpg

    If you don't measure then you don't know.

    #40 1 year ago

    Deleted - I saw a NTE395 at Digikey, but noticed it was discussed earlier.

    #41 1 year ago

    Why continue with the old linear regulators ? Replace them with a decent dc-dc converter: more efficiency, cheaper, little heat and easy to find with a 5V/5A output.
    Did it for several machines already: Bally, D.E., Gottlieb ...

    #42 1 year ago
    Quoted from PinMario:

    Why continue with the old linear regulators ? Replace them with a decent dc-dc converter: more efficiency, cheaper, little heat and easy to find with a 5V/5A output.
    Did it for several machines already: Bally, D.E., Gottlieb ...

    You mean like this one that was already discussed? https://pinside.com/pinball/forum/topic/replacement-for-the-ml338k-wanted#post-7638156

    #43 1 year ago

    yes, sort of. They come in many flavors. Once used a 5V/10A converter to replace the regulator on a D.E. power supply, has been working fine for years now. If interested i can look for the photo's. Also did a similar replacement as in the photo for Bally power boards.

    #44 1 year ago
    Quoted from mbwalker:

    Deleted - I saw a NTE395 at Digikey, but noticed it was discussed earlier.

    More times mentioned the better

    #45 1 year ago
    Quoted from PinMario:

    yes, sort of. They come in many flavors. Once used a 5V/10A converter to replace the regulator on a D.E. power supply, has been working fine for years now. If interested i can look for the photo's. Also did a similar replacement as in the photo for Bally power boards.

    Yes, I have used them in several machines, works fine. Very nice that you can adjust the voltage.

    #46 1 year ago

    I'm sure that many owners like myself prefer to keep their machines original. I say, if you want a machine with the latest technology, I.E. such things as high efficiency switching mode power supplies, LC Displays, LED's, etc.etc. etc. buy a modern machine. The now, "old school" technology in earlier models is part of their charm. If the original power supply was designed around an LM338K, then that's what it should be replaced with (at least until the very last one has been depleted, or hoarded)

    #47 1 year ago
    Quoted from Mthomasslo:

    I'm sure that many owners like myself prefer to keep their machines original. I say, if you want a machine with the latest technology, I.E. such things as high efficiency switching mode power supplies, LC Displays, LED's, etc.etc. etc. buy a modern machine. The now, "old school" technology in earlier models is part of their charm. If the original power supply was designed around an LM338K, then that's what it should be replaced with (at least until the very last one has been depleted, or hoarded)

    I like original boards for the most part because most are well documented and repairable.

    However, I think you may have overlooked the point of this discussion. The main problem is the LM338K *isn't* readily available, hence the need to find a substitute or alternative solution. Otherwise it would be a no brainer to drop in the same regulator as a replacement.

    #48 1 year ago

    I do like the replacement with the Buck Step-down regulator.
    Direct information with the voltage indicator and voltage adjustment possibility.
    Nice clean look with minimal "hack" work.

    I've ordered 10 of the Buck Step-down boards from Ebay.
    I know, it Chinese stuff, but it is so darn cheap I need to test it.
    ebay.com link: itm
    I'll put up some images when they arrive and build in the game.

    LM338K vervanger (resized).jpgLM338K vervanger (resized).jpg
    #49 1 year ago

    Here's a Bally/Stern power board with a 5A DC converter and a D.E. powerboard with a 10A DC converter
    On the D.E. board several other components of the 5V regulator circuit where removed because not needed anymore. The display was for testing and removed after a while. I also added a larger capacitor on the outgoing 5V line. Not the best looking but it was a first attempt

    Bally (resized).jpgBally (resized).jpgD.E. (resized).jpgD.E. (resized).jpg
    #50 1 year ago

    Although I was looking at a drop in replacement (NTE395) for the OP, personally I wouldn't have any qualms using a quality DC-DC switcher. But I don't know the OP's skill level, so I'm always a little leery of suggesting making electrical mods. We've all seen the hack thread.

    One of the best reasons to use a linear regulator is when you need a very quiet supply. But even then, I've used a switcher to get the voltage dropped to a lower voltage, the clean it up w/a linear regulator after that.

    There are 72 posts in this topic. You are on page 1 of 2.

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