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  1. #31
    ic-racer's Avatar
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    Only reason the board is not ready to go is that I discovered a slight error in my selection of the replacement chip for the 'Dual NOR driver' UDN-5714M.
    This component is not available from Mouser, CEI or Digikey, and I'm still looking for them. I thought the 75454b would be a replacement and ordered them, but on examining the datasheets, there is a discrepancy at pin #6.

    Last edited by ic-racer; 03-18-2009 at 11:10 AM. Click to view previous post history.

  2. #32
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    While waiting to source the above parts I did an overhaul of my 3 working heads. Now they all zero in on the filtration quickly and are very stable. I replaced the electrolytic caps in all 3 boards. The biggest improvement in stability was to set the 'offset voltage' in the color probes. The manual contains many errors in the procedure and for years I could not figure it out. I finally sat down with the schematic and a 'test head' and figured out all the errors in the shop manual and was able to set the value. Looking at the corrections in my manual, it looks like I could compile quite a long list of errors. Perhaps I'll put these together and post them if there is interest.

    One of the heads also had a bad rubber wheel which I repaired.

    Coincidentally, there was a post yesterday on the Large Format forum indicating that new rubber wheels are still available from Omega (number 800-777-6634). I'll have to check that out for spares.

  3. #33
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    I had previously posted that the board that fried light bulbs had a cold solder joint on the connector pin to the light enters the board. I discovered the same condition on another board also. Looks like this is a common failure point. I re-soldered this connection on all the boards.

    Now I know how that was causing the lamp failures. The high resistance connection caused the RMS voltage sensor to ramp up lamp voltage until it arced across the connection. This illuminated the lamp with a high voltage, and the system is not quick enough to ramp the voltage down again and the bulb blows.

  4. #34
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    I realized that used care in removing all the old components (just in case some would be hard to source), so I cleaned up the legs of the three old UDN-5714Ms and popped them in the sockets and it checked out find.

    So, at least I proved to myself that a complete component-for-component rebuild is possible and affordable. Components were about $30.

  5. #35
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    As I was fixing these heads up I noticed the bulb socket contacts were black from oxidation. I spent about an hour polishing the contacts and applying DeOxit. I saw a number on the socket "QLV-1" and looked it up. It turns out this is a readily available socket. I will have to pick up one as a spare.


  6. #36
    ic-racer's Avatar
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    I also found a place that has the TD62479P (a cross reference for the SN75479N )

    Not too bad, $5 each. http://www.utsource.net/

    I had a quote from another place that wanted $20 each, minimum order of 10.

  7. #37
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    Just an update on this thread. I was finally able to do the transaction for the Dual NOR Gate components. It turns out the place is in China, and the parts should be arriving shortly. Shipping and transaction fees brought the price to $10 per chip. That is actually not that bad, as the RMS CONVERTER chip cost $13 itself.

    Too bad I could not get these from a USA source. I found the chips at 3 USA sources but all 3 businesses were holding the chips for ransom to the tune of $250 to $500.

    Testing the old components removed from my re-furbished board has shed insight on the initial failure of the board 9 years ago. I'll know for sure once the new chips arrive and will post the answer after I double check things.

  8. #38
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    Ok, an update here. I ordered three of the TD62479P chips from China. These chips have the same logic function as the original, but for some reason (input or output impedance) they did not work.

    On a whim I called Omega/Satter and I was very surprised to find that they actually DO carry the replacement UDN-5714Ms chip for the D5500! What an odd-ball thing, as they don't have any other D5500 parts (besides the rubber roller wheels).

    I ordered the chips and they should be arriving shortly.

  9. #39
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    Conclusion:

    I put the 3 new UDN5714m chips in the board and .... it works perfectly! So, as Murphy would have predicted, the 'most difficult to locate' chip was the culprit! This finding does lend some closure to the fact that at the start of the project, the only part on the board with visible damage was the burned resistor that carried current to the UDN5714m chips.

    Where to go from here? Well, in the never-ending-circus-ride-of-perfection, I see that the lamp voltage in this newly re-built board is absolutely rock solid. On the other boards, the one-tenths digit of the voltmeter jumps around a little when setting the lamp voltage. I ordered multiples of many of the parts, so I think I am going to go ahead and re-build another of my 4 boards. Probably the one with the least-steady lamp voltage.
    Last edited by ic-racer; 04-29-2009 at 02:40 PM. Click to view previous post history.

  10. #40
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    OK, so that first board that I did has been in service for about a year and is working fine. I had planned on doing this total re-build to two boards and I just completed the component removal of the second board yesterday.

    So, the goal is to have a 'brand new' power supply in each of my main heads.

    Of course realizing that this type of rebuild is a little bit of an 'odd-ball' thing. Usually the defective component would be located and replaced. In this case, though, since the power supply lives up in the head with the 250W light, I wanted to replace ALL components on the PC board, so that they would likely outlive me. Also, the cost to replace every component (except the transformers) is only about $35.

    Component removal went much faster this second time. I had no intention of saving any of the ICs or other components as they are all currently available new or NOS from USA suppliers. I just clipped the legs, removed the component, then de-soldered the legs. This allowed me to maintain the integrety of nearly all the 'through-hole' copper traces that connect the top and bottom of the board.

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