Rotten dog power supply voltage

(Topic ID: 237827)

Rotten dog power supply voltage


By Doggy

16 days ago



Topic Stats

  • 17 posts
  • 4 Pinsiders participating
  • Latest reply 8 days ago by G-P-E
  • Topic is favorited by 1 Pinsider

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    #1 16 days ago

    I have a problem with my system 1 rottendog power supply, while testing the 60 volt pin my hand slipped and I inadvertently hit either the ground or the 42 volt pin. It gave off a little spark. Then I had no voltage coming out of the 60 or the 42 pins.
    I installed a new HV regulator LM317AHV and now I get 58 volts from both pins.. could I have fried something else when my hand slipped?? I can’t adjust the voltage like you can with the original power supply. Any suggestions would be appreciated..

    #2 16 days ago

    If it's new I would contact rottendog.

    #3 16 days ago
    Quoted from Doggy:

    I have a problem with my system 1 rottendog power supply, while testing the 60 volt pin my hand slipped and I inadvertently hit either the ground or the 42 volt pin. It gave off a little spark. Then I had no voltage coming out of the 60 or the 42 pins.
    I installed a new HV regulator LM317AHV and now I get 58 volts from both pins.. could I have fried something else when my hand slipped?? I can’t adjust the voltage like you can with the original power supply. Any suggestions would be appreciated..

    You also killed the 18V Zener-Diode 1N4746A - replace it and your 42 V should be back. Could you post a photo of your board, mightbe, you also killed a resistor "behind" the regulator.

    And there is no poti for adjustment as on the original.

    #4 16 days ago

    The 18V Zener-Diode 1N4746A is CR12 correct? I’ll have to order that.. here’s a pic...

    820708B1-0C24-438B-BABA-14188E563CED (resized).jpeg
    #5 15 days ago

    Yes, CR12 = 1N4746A, an 18V zener.
    If you do not have 60V then you will also not have 42V.
    Replace the 60V regulator first then worry about CR12.

    Yet another LM317AHVT bit the dust due to regulator exceeding absolute maximum ratings...

    #6 15 days ago

    I did replace the LM317AHVT. Before I changed it I HAD -0- volts from 60volt pin and the 42volt pin.
    After I changed the regulator I got 58 volts from both pins..could I have gotten a bad LM317AHVT??
    Or is 58 volts acceptable?? Next I will replace the 18V Zener-Diode 1N4746A .. thanks for your help guys...

    #7 15 days ago

    58 is fine - you are within 5% of target voltage.
    If the 42V is reading 58V then CR12 is shorted and also needs to be replaced.

    #8 15 days ago

    Thanks again G-P-E. I’ll change cr12 out and hope alls well again...

    #9 11 days ago

    Thanks G-P-E and German-pinball I changed out the 18V Zener-Diode 1N4746A and 60 volt regulator LM317AHVT and the power supply is up and running again..this site has a wealth of information and a bunch of members eager to share their knowledge which makes this hobby awesome...

    #10 11 days ago

    FYI -- LM317AHVT is on the end of life list from the manufacturer. I suspect there will be a last time buy issued within the next few months (if it hasn't been issued already).

    #11 11 days ago
    Quoted from G-P-E:

    FYI -- LM317AHVT is on the end of life list from the manufacturer. I suspect there will be a last time buy issued within the next few months (if it hasn't been issued already).

    My few cents: LM317AHVT is a bad choice in the HV-section. Imho that is no improvement.

    Better way is to go the "traditional" way; good old series pass transistor type regulator (will never be end of life product and always be available) with extra current fold back circuit - thats the way how it has to be done.

    Only alternative for SYS-1 machines could be a TL783-design - only my few cents.

    #12 10 days ago
    Quoted from german-pinball:

    My few cents: LM317AHVT is a bad choice in the HV-section. Imho that is no improvement.
    Better way is to go the "traditional" way; good old series pass transistor type regulator (will never be end of life product and always be available) with extra current fold back circuit - thats the way how it has to be done.
    Only alternative for SYS-1 machines could be a TL783-design - only my few cents.

    I absolutely agree and have been speaking against using LM317AHVT's (and LM337T's for negative HV) for quite awhile.
    For Gottlieb System 1/80 games - the TL783 is a good choice. Only minor downside is that the part is sole sourced by Texas Instruments. But TI tends to keep parts around longer than other manufacturers.

    The series pass regulators are the only way I will ever go for HV supplies. These work great as long as there is current limiting (shame on you Bally and Williams!).
    However, Pascal has yet another alternative. He uses a boost type switching regulator up step up lower voltage (12V I think) into the 60V for his all in one Gottlieb board. I like this idea also but I doubt I'll ever go that route.

    #13 10 days ago

    So those of us who invested in the rottendog PS, which regulator would you suggest when/if the LM317AHVT malfunctions? Also if we change out the LM317AHVT regulator, is there other components you must change also??
    I know the obvious answer is stay away from the power supplies which use that regulator, but if you already have it what would be the best modification??

    #14 10 days ago
    Quoted from Doggy:

    So those of us who invested in the rottendog PS, which regulator would you suggest when/if the LM317AHVT malfunctions? Also if we change out the LM317AHVT regulator, is there other components you must change also??
    I know the obvious answer is stay away from the power supplies which use that regulator, but if you already have it what would be the best modification??

    Simple answer: You should put a few LM317AHV in stock for replacement.
    You cannot simply replace it by e.g. TL783 without changing parts around it; that would require modifications on the board.

    #15 9 days ago

    Thanks German-pinball I have 2 system 1’s. I will buy a couple LM317AHVT just in case. But for my future projects I’ll stay away from those power supply’s that use the LM317AHVT regulator’s thanks to you and G-P-E for the heads up.

    #16 9 days ago
    Quoted from Doggy:

    So those of us who invested in the rottendog PS, which regulator would you suggest when/if the LM317AHVT malfunctions? Also if we change out the LM317AHVT regulator, is there other components you must change also??
    I know the obvious answer is stay away from the power supplies which use that regulator, but if you already have it what would be the best modification??

    Quoted from Doggy:

    Thanks German-pinball I have 2 system 1’s. I will buy a couple LM317AHVT just in case. But for my future projects I’ll stay away from those power supply’s that use the LM317AHVT regulator’s thanks to you and G-P-E for the heads up.

    I thought a bit about it - and it is easy to change to TL783C-design, when LM317AHVT will become obsolete!!!!

    LM317AHVT and TL783C are pin compatible, so it is easy, to modify the RD board to TL783C-design without any modifications to the board!!!

    1.) Replace capacitor C6 (220uF) to 10uF /100V capacitor
    2.) Replace voltage regulator U1 (LM317AHVT) to TL783C
    3.) Replace resistor R4 (215R) to 470R / 1/4W
    4.) Replace resistor R3 (10K) to 22K / 1/4W
    5.) Add Diode 1N4004 to the legs of the new TL783C - Cathode to Pin3 (IN) and Anode to PIN2 (OUT) - recommended, but not necessary

    A 2-bucks modification .... pretty easy, isn´t it?

    #17 8 days ago

    Pretty good but a couple issues when going to a TL783C.
    With those resistors - you are running at 59.45V... quite close to desired voltage.
    Across those two - you are running about 2.67mA.

    1 -- the easy issue:
    For R3 -- you would need to go to at least 1/2W for that one.
    At 1/4W, you're running at just over 50% load.

    2 -- the not so easy issue:
    I used these in a design for house arrest GPS tracking system many years ago (ankle bracelets linked to a special cell phone). The tL783s were used in the base unit - breath analyzer with video and cell phone lock/charging station. This was one of the most fun projects I ever worked on and even had a half page article in USA Today newspaper. The best part was putting through lots of testing - including the breath analyzer.

    The TL783's are quite reliable but have one issue: They have a minimum load current. If you are below the minimum load current then the voltages go out of whack. If you don't get close to the minimum load - the voltage was always off (I can't remember if it was too high or too low).

    The listed minimum current is 15mA. You would need to go down to the range of R4 at 100R and R3 at 5.1K. This would get you closer at 11.4mA (spec wise, still low but closer). R4 could be rated for 1/4W still (dissipating just over 0.013W). But R3 would be running at 0.66W so need at least a 2W resistor there. At 2W, this would make the resistor into a little space heater. so 5W would be preferred.

    The other option is to stay with the 470/22K divider resistors and add a 4.7K, 5W load resistor to the board. This would add about 13mA load at the board output and would hold the regulator within the target voltage range. Again, nice little space heater.

    Just no easy way around this second issue.
    Ed

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