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Thread: ILT 5405A filament transformer taps

  1. #1
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    Default ILT 5405A filament transformer taps

    Does anyone know what taps I need to use on the filament transformer to rewire it for 240V? Its presently tapped for 208V

    The small transformer I have moved the 230V tap to the 240V tap but there is also a wire connected to the 200V in tap - should I move this guy as well? The output of this transformer is 115V - I assume looking at where it goes, its to buck the voltage to power the fans as thats where the blue wire leads - to the umbilical. Two pins - I assume one for the side fans, and the other for the top one. I don't see what other purpose this transformer serves. My laser head has 240v fans. Either I could swap the fans, or bypass this transformer. The latter is the cheaper option.

    edit: ok I worked out that the SSR and interlock board turn on the filament transformer and I need to move the grey wire.

    BTW I read someone here blew their SSR and replaced it with a switch. I have spares of these (about 4) so if you need one drop me a line.

    I also learned that the PSU fan is powered by the middle board inside the PSU. So moving that blue wire to 240 should run 240V fans on the head.

    TIA
    Last edited by dash8brj; 11-10-2017 at 14:55.

  2. #2
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    Let me check. I went out to visit ilt in Utah and brought back schematics and drawing. Have to find them.

  3. #3
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    thankyou so much kecked - that would help immensely.

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    I’ll look harder but I don’t see it where I expected it. This is a guess but I bet you can figure it out with a volt meter looking at the resistance. See if there is continuity between all the taps. If not it’s split wound. Doubt that on the primary. Then map the resistances and you should be able to determine which Wrap has more or less resistance from which tap. This way you can find the primary ends and then the taps between. Try looking at the ratio of theresistances to see if it makes sense for the taps you want. Pure guess. Not tried. Your mileage will vary.

  5. #5
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    I'm guessing it should work like an auto transformer, so if I measure from the neutral input and progressivly check each tap around the transformer I should be able to find the 240V one. I will have a friend on the mains switch and be wearing gloves to be on the safe side.

    This would be easy to do by removing all the boards (been there done that to check for blown up parts) and bypass the ssr. Also a check of the filament voltage (should be between 2.5 and 2.6v possibly a bit higher due to no load, should identify if its on a 208v or 230v tap (my suspicion considering the small transformer was tapped for 230). If the filament voltage is like 3.5 etc, I'll know its on the 208V. if its 2.8 ish, I'll know its on 230. What confuses me is the inclusion of an input on the 200V tap as well on the small transformer. The first thing I'll do when I pull it to bits again is map out where the 200V connection on the small transformer goes. If its to hot, I'll remove it and insulate it. I could understand if they were being smart and using the 200V tap with 115v AC input to slow down the fans, but over drive them?

    Either way I'll try your way first, as that way is safer

    Heres my ohm readings:
    Transformer Pin 1: Neutral
    Transformer Pin 2: 4.8R
    Transformer Pin 3: 5.6R
    Transformer Pin 4: 6.3R
    Transformer Pin 5: 5.6R (shorted via jumper to pin 3)
    Transformer Pin 6: 9.2R (connected to SSR output)
    Transformer Pin 7: 10.1R
    Transformer Pin 8: 10.6R

    My guess is move the grey wire goes to pin 8. Pin 8 is also connected to the low noise board, which has 450WV capacitors on it. What do you reckon?
    Last edited by dash8brj; 11-10-2017 at 19:44.

  6. #6
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    kecked: please see edit above

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    The largest resistance means the most turns. So...that I would think would be the lowest input voltage as the large number of turns would give the largest boost. The lowest resistance would the the highest input voltage. Make sense? So start with the lowest resistance and go from there. What is you voltage over there? 220? If so look for aresistance about double the lowest.

    Maybe put a current limiting resistor in line with the input and move from pin 2 up till it measures right on the secondary side? Once you have it sorted map it and post here for everyone else down the road.

    An autotransformmer might be a. good idea too.

  8. #8
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    The power over here is 240V. We are stepping down. We moved the tap and did power on tests (with just the filament transformer & fan connected and got these readings:
    Tap 6 (original) 264V to LNB, 3.5V Filament - Fan ran slightly over speed
    Tap 7 252 volts to LNB, 3.4V Filament - Fan ran slightly over speed
    Tap 8 240 volts to LNB, 3.3V filament. - Fan ran correctly

    LNB stands for Low Noise Board - its the PCB in the middle of the triple stack with the hall sensor and large inductor on it.

    The fan is run of a different tap, and gets 115V ac (not measured, but sounded like DashApple's supply on LPF).

    The original wiring was for 210 volts, and 9.6 ohms. Tap 7 10.2 Tap 8 10.6 so I think you have the equation back to front.

    The LNB has a 230V mains input PCB transformer and 240V is well within tolerance. Judging by the 450V caps on this board, I think I have selected wisely. What are your thought.

    SUCCESS!!! it worked! 2.6v on the cathode! now I just need to get some 115V fans and fix the start card (probably the SCR as its not ticking) and I'll be all set

    During power up the filament heats and can be seen glowing nicely down the bore (yes I timed prior how long the laser took to apply anode voltage so my eyeball was clear of the beam path well before this!). After anode voltage is applied, it rapidly climbs to 330 ish volts, but no ignite pulses, so this tells me its got something to do with the start board. Like I said its probably the SCR thats dead.
    Last edited by dash8brj; 11-12-2017 at 14:56.

  9. #9
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    Glad you got it sorted and now there is a record for others to find. Like I said was pure guess. I just figured more resistance is more windings. But thinking about it. More windings in primary means lower ratio with s3condary so yup backwards thinking.

  10. #10
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    Idea next time you look down the bore use a piece of glass and paper and look at the paper for the flash. Lot safer.
    Use th glass like a beam splitter and the paper to see the flash or use an old camera in video and look at that. One set of eyes...

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