(Topic ID: 230706)

SOLVED - Transistor Coding Question


By JethroP

6 months ago



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  • 14 posts
  • 6 Pinsiders participating
  • Latest reply 6 months ago by Homepin
  • Topic is favorited by 1 Pinsider

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    #1 6 months ago

    I am looking to replace Q2 in a Gottlieb System 1 power supply. The parts list calls out MJE340K. I am trying to find out what the K suffix means. I have found lots of info on transistor coding, but nothing regarding the suffixes. I have access to an MJE340G but not sure if that is an acceptable replacement. I have also read the TIP85 is an acceptable substitute. But my question is....what does the suffix designate?

    #2 6 months ago

    I would suspect it's the package. That's usually how it works. The MJE340 being the transistor itself.

    #3 6 months ago

    Suffix depends on the specific manufacturer.
    MJE340G would be the current generation On-Semiconductor parts. "G" = "Green" or lead free with a TO-225 body style.
    On-Semi inherited the Fairchild Semi MJE340S components for a TO-126 body style.

    Both TO-126 and TO-225 are very similar in body style.
    Differences:
    MJE340S parts have three dots on front to indicate front of transistor. Standard pinout - Left to right = Base, Collector, Emitter.
    MJE340G parts have a heat slug to indicate back side of transistor. Same pinout.
    Sometimes you will see a "TU" at the end of the Fairchild parts (e.g MJE340STU). This simply means the parts are shipped "Tube" packaged.

    "K" suffix typically means it is a TO-3 transistor. But the MJE340 does not use a TO-3 style case so the parts list is using some old suffix from a no doubt defunct manufacturer.

    #4 6 months ago

    Thank you for the explanation!!

    #5 6 months ago
    Quoted from JethroP:

    I am looking to replace Q2 in a Gottlieb System 1 power supply. The parts list calls out MJE340K. I am trying to find out what the K suffix means. I have found lots of info on transistor coding, but nothing regarding the suffixes. I have access to an MJE340G but not sure if that is an acceptable replacement. I have also read the TIP85 is an acceptable substitute. But my question is....what does the suffix designate?

    Hello,
    Regarding the above answers about the suffix, I agree ... but on the other hand, on an original power supply for Gottlieb SYSTEM-1:
    Q2 is not a MJE340 but a TIP31C
    and if the package is similar (TO-220/TO-225), the characteristics are very differents.
    2018-12-03_09h22_39 (resized).png
    The TIP31C is a high-power NPN transistor, voltage limit is 100 V and current is about 3 A (peak 5 A).
    The MJE340 has a voltage limit to 300 V (OK !) but a current limit to 500 mA , so sure it's not suitable

    Sometimes, the suffix indicate a variation in the basic characteristics (speed) but I doubt that a MJE340K will be able to drive 3 A.

    TIP85 a subsitute ??? but what is a TIP85 ? This transistor reference doesn't exist

    Not only the power is not at all the same, but the pinout of a MJE340 has nothing to do with that of a TIP31C. Base and Emiter pins are crossed :
    fdgsdg (resized).png

    Check your board : if it's really an original power SYSTEM-1 from Gottlieb, Q2 can't be a MJE340.

    #6 6 months ago
    Quoted from noflip95:

    Hello,
    Regarding the above answers about the suffix, I agree ... but on the other hand, on an original power supply for Gottlieb SYSTEM-1:
    Q2 is not a MJE340 but a TIP31C
    and if the package is similar (TO-220/TO-225), the characteristics are very differents.
    [quoted image]
    Check your board : if it's really an original power SYSTEM-1 from Gottlieb, Q2 can't be a MJE340.

    Not only do I believe I have an original System-1 power supply from Gottlieb, but the service manual I have and the drawings and parts list (attached) show Q2 to be a MJE340K.

    So you are saying I shouldn't use what my drawing shows?

    Also, my mistake....I meant NTE85 not TIP85. Can I substitute TIP85 for 2N3416. All this electronics stuff has me rattled! Thanks for the help.

    IMG_9658 (resized).JPGIMG_9659 (resized).JPGIMG_9660 (resized).JPG
    #7 6 months ago

    The resistors at R10 and R11 are also different between the two schematics (15k ohm on yours vs 10k ohms on the other schems). Question is which schematic matches the power-supply you have? Can you post clear pictures of your P/S board?

    The max collector-emitter voltage on the NTE85 is 30 volts while for the 2N3416 at Q3 it's 50 volts. Not a direct substitute.

    #8 6 months ago

    Here is my board. CR10 is currently missing because I am replacing it.

    IMG_9665 (resized).JPGIMG_9666 (resized).JPG

    #9 6 months ago

    Your R10 and R11 resistors are both 10k ohms. Unfortunately transistor Q2 is out of picture so we can't tell what it is.

    #10 6 months ago

    Here is schematic showing the rest of the circuit. I see other resistors are different than other schematic versions (R16, R17). Now I have even more questions about substitutions. Are Q2 parts interchangeable....MJE340k vs TIP31c? Should I change resistors? Are there any other substitutions for Q3, 2N3416?

    IMG_9667 (resized).JPG
    #11 6 months ago

    What transistor have you got at Q2? You cut the part number off in your board picture above (it's at the bottom of that picture screwed to the metal plate) so we can't see what you currently have. Go with a TIP31C.
    Regarding the 2N3416 at Q3, we didn't determine that it was faulty. GPE sells them for $0.12 each (min qty 2pcs). Pull it out and test it in diode mode with your multimeter to see if it's faulty.

    https://www.greatplainselectronics.com/proddetail.asp?prod=2N3416

    #12 6 months ago

    I replaced Q2 with TIP31C and now have all correct nominal voltages! Thank you!!! So I will be powering up the rest of the game for the first time shortly.

    #13 6 months ago

    So I've connected the power supply to the CPU board and am following Clay's guide regarding powering up the game for the first time. I'm going to create a new topic about the problem I am now experiencing, and hope you can help me along there too. I think this thread is solved.

    #14 6 months ago

    A word of caution here for those that may not be aware. In the case of most 'TIP' transistors the suffix letter is very important. Looking at part of the On Semi spec sheet below we can see that:

    TIP31A is rated at only 60V
    TIP31B = 80V
    TIP31C is 100V

    TIPABC (resized).jpg
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