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Voltage Regulator Problem on Moving Head mainboard

Discussion in 'Power Electronics' started by partyanimallighting, Jul 18, 2020.

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  1. partyanimallighting

    partyanimallighting

    319
    4
    Oct 22, 2012
    Hi guys, I have a problematic moving head with non-functioning shutter, focus and zoom stepper motors. There is one specific mainboard that drives these stepper motors and the 28VDC coming into this PCB is fine so I'm guessing it's the voltage regulator that's feeding the stepper motors and the two DC cooling fans that's problematic. I've tried searching for a datasheet for the voltage regulator so I can have an idea as to voltages out and pin layout but I'm not getting anything, maybe my Google ability has the virus. Can anyone tell me if they're familiar with this particular regulator? If I at least get a datasheet I could check voltages or at least try a substitute with similar voltages that might work.

    2020-01-04 20.51.51.jpg 2020-01-04 20.51.39.jpg 2020-01-04 22.02.61.jpg
     
  2. Martaine2005

    Martaine2005

    2,815
    754
    May 12, 2015
    My Google has suffered the same fate!.
    Absolutely nothing.

    Shame you don’t have another to compare with. My mobile disco had two of everthing for symmetry.

    Do you have any other equipment by Chauvet?, they probably use custom or disguised components. Latter more likely.

    Edit: I have a Chauvet unit but can’t remember what it is. I’ll check it in an hour.

    Martin
     
    Last edited: Jul 18, 2020
  3. bertus

    bertus Moderator

    745
    264
    Nov 8, 2019
    Hello,

    The closest I could find is the TD7590.

    Bertus
     

    Attached Files:

    Martaine2005 likes this.
  4. Martaine2005

    Martaine2005

    2,815
    754
    May 12, 2015
    Sorry, my unit is of no use. It’s the old PC-08 power distribution panel. (Switch panel).

    Martin
     
  5. partyanimallighting

    partyanimallighting

    319
    4
    Oct 22, 2012
    Hi guys. Thanks for the fast feedback. The good news is, I myself like symmetry so I do have two units but the other unit had a lamp strike problem. This problem was caused, strangely enough, by two small 3 wire 60MM sensor fans located in the front of the unit that I assumed were not the cause of the problem (how wrong I was). These fans, when they're faulty, caused the lamp to douse maybe about a minute after lamp strike. So I solved this problem by replacing these fans in both units. All the terminals on these pcbs are not regular JST so I had two choices, cut and join the fan wires to replace the terminals or replace the terminals on the pcb. Seeing that all the replacement fans have a 3 pin Molex connector, I replaced the terminal sockets on the pcb. Problem solved. Anyway, back to the issue at hand. I tested the faulty pcb in the working unit and the problem followed the pcb. So I took some voltage readings off the regulator for comparison so the readings are attached. The readings don't seem to be too "off" between the two pcbs so I also checked the voltage out at the fan terminals. 11.75VDC, working pcb. 7.5VDC, faulty pcb. I'm still thinking faulty voltage regulator but you guys are the experts and I'm hoping you can advise me as to what direction to head in or maybe suggest a replacement regulator.:confused::confused:

    2020-07-16 REGULATOR VOLTAGES.JPG
     
  6. partyanimallighting

    partyanimallighting

    319
    4
    Oct 22, 2012
    Did I mention that this pcb is $140.00 from Chauvet Parts plus overseas shipping and Customs and handling charges? Hence my wanting to repair the pcb if it's a simple enough problem like a blown regulator.
     
  7. Martaine2005

    Martaine2005

    2,815
    754
    May 12, 2015
    Wow, but that price doesn’t surprise me.
    I looked briefly at the datasheet that @bertus linked to.
    On the TD7590, GND is pin 2. You have 12V on pin 2 on both units.
    Can you verify which is GND on your TD7591?.
    F/back is pin 4 on the 7590. The threshold voltage is 1.2V which you have on the good unit and 0.2V and the non working unit.
    None of this means much without knowing the pinout of your unit.
    If pinouts are the same, there is no feedback.
    Pin 5 is EN. Enable turns the chip on/off.
    Can you measure the good units pin 5 while controlling the head, shutter or focus steppers?. Pin 5 should go high.
    We are just trying to find out the pins. If the chip turns on do the same on the bad unit.

    Martin
     
  8. partyanimallighting

    partyanimallighting

    319
    4
    Oct 22, 2012
    Hi guys, I took some continuity readings off the regulator on the working PCB and I've posted them in the attached image. I then powered up the unit and measured voltages on pins 1, 2 and 4 and attached these also so I hope this helps. Martaine2005, I took the voltage readings by attaching individual wire leads to the relevant pins so I could test the voltages as you suggested (it was voltages you meant right?) whilst controlling the shutter, zoom and focus motors but I saw no significant rise in voltage whilst controlling the relevant motors. Seeing that I'm "not a technician", is there a better way I could have done this besides soldering these leads? (Note: working by myself). I did not test pins 3 and 5 as I'm getting continuity between these two pins and also each pin to the ground tab.
    Based on the continuity test I did with OL and 600Ω readings on pin 4, can I assume that this leg is the gate?

    I hope this image helps.....

    TD7591S-ADJ REGULATOR VOLTAGES AND CONTINUITY.JPG
     
  9. 73's de Edd

    73's de Edd

    2,879
    1,217
    Aug 21, 2015
    That 7591 units "ringing" inductor is being the black ferrite dumbell 330 uh that is located just below and to the left of it.
    Then, spaced off to the left from the 330 is being the main DC collection and reservoir E- capacitor (470ufd / 16VDC ) can for your whole 12VDC supply.
    Check and see if passage of use time and past times furious and brutal switching demands has likely knocked it on down to almost being flat out of effective capacitance, due to its developed ESR.
    Sub in another like capacitance E-cap. . . . . see the fan fly.
     
    Last edited: Jul 20, 2020
  10. partyanimallighting

    partyanimallighting

    319
    4
    Oct 22, 2012
    Hi 73's de Edd. You have helped me before in the past so it's good to hear from you and get your input also. So you think it's probably the capacitor and not the regulator? I understand what you're saying, that wear and tear have broken down the functionality of the capacitor but the thing is, these units are practically new with a few hours on them, 200+ hours if so much. I was probing around a little further into this original faulty unit which also had a lamp dousing problem caused by faulty 3 wire cooling fans and I've discovered that the fans had corroded and broken wiring solder points under the labels which seemed to have shorted out and I'm thinking that this is the cause of the actual problem. The + and - wires seemed to have come loose and were probably touching each other below the label. I'll take your advice and see if I can find a suitable cap to replace but if I can't find one can I use a regular ecap with the correct values to test? I'll report back as soon as I can.
     
  11. Martaine2005

    Martaine2005

    2,815
    754
    May 12, 2015
    Yes, good call Ed.
    I never thought about caps as these units are 2017 and newer.

    You can use any Ecap with same values.
    On through hole, I just tack another cap across the suspect for initial testing. You’ll need to remove yours.
    An easy way to remove them is with pliers and twist them off. Clean pads after. Never had a problem with solder pads.

    Martin
     
  12. partyanimallighting

    partyanimallighting

    319
    4
    Oct 22, 2012
    Hey guys, I found a 16V 470UF ecap off an old pcb and tested it before I soldered it to the pcb across the existing cap. I booted up and tested and the problem is still there, no changes. So that suggests to me with my little knowledge that it's not the cap and it points back to the regulator (????). I did not remove the existing cap because once I twist it off, I'll have to find a replacement aluminum cap locally and that's probably impossible locally, which means I'll have to order from overseas and that'll be a few weeks.

    16V 470UF 003.jpg
     
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