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Thread: Repairing a cursed Polaroid 8x10 processor

  1. #1

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    Feb 2013
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    Repairing a cursed Polaroid 8x10 processor

    Hi everyone,

    I've been using the time in lockdown to go through my unfinished projects to complete them and I've come across my Polaroid 8x10 processor that seems to be cursed and has been sitting broken in a box for the past 7 years. It's a US unit (110V) but I live in Europe (220V) and the person I bought it from plugged it straight in the mains blowing the fuse. Moreover, the unit was battered badly during transit, cracking both the main drive gear and the plastic holders for the roller assembly. I was able to use bondo to repair the gear the plastic holders, but I'm not so lucky on the electronics front.

    I replaced the fuse and used a step down (220V -> 110V) converter to try and power it up but it immediately resulted in smoke and a bad smell. Upon inspection it seems like a capacitor on the relay board was blown (or at least, I assume it is a capacitor. The one next to it that looks identical and survived is labeled ZNR K241 27). I've read multiple threads on this board about replacement of the oil filled capacitor used to drive the motor. That is something I should probably also do, but does not seem to be related to the malfunction of this particular unit.

    Given I used the correct AC in voltage, does anyone know what could be the culprit here?

    Any help is much appreciated!

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  2. #2

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    Re: Repairing a cursed Polaroid 8x10 processor

    Is the motor 50 or 60 cycle? Its not just voltage.

  3. #3

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    Re: Repairing a cursed Polaroid 8x10 processor

    Quote Originally Posted by Bob Salomon View Post
    Is the motor 50 or 60 cycle? Its not just voltage.
    How can I find that out? Worth noting is that I have another US 8x10 processor that does work fine off the same step down converter.

  4. #4

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    Re: Repairing a cursed Polaroid 8x10 processor

    Quote Originally Posted by Matthijs View Post
    How can I find that out? Worth noting is that I have another US 8x10 processor that does work fine off the same step down converter.
    It will say it on the power label on the unit. Usuall by where the cord enters the unit or on the bottom.

  5. #5

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    Re: Repairing a cursed Polaroid 8x10 processor

    Quote Originally Posted by Bob Salomon View Post
    It will say it on the power label on the unit. Usuall by where the cord enters the unit or on the bottom.
    It says 120 VAC 3.5 Amps 50/60Hz, same as my other unit which is working with the step-down converter. Is the Hz rating what you were referring to?

  6. #6

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    Re: Repairing a cursed Polaroid 8x10 processor

    That's not a capacitor but a varistor. It's used as a overvoltage protection. So if the circuit was for 110V and they put 230V on it, then it is logical they are defect. You should change them both.

    The "241" would be the voltage rating which is 150VAC for a "241" so typical for 110VAC circuit protection. Get one with the same or slightly larger size because the size is what determines their power adsorbing capacity.

    But if that component was blown that others might as well be defective.
    Expert in non-working solutions.

  7. #7

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    Re: Repairing a cursed Polaroid 8x10 processor

    Quote Originally Posted by Matthijs View Post
    It says 120 VAC 3.5 Amps 50/60Hz, same as my other unit which is working with the step-down converter. Is the Hz rating what you were referring to?
    Yes

  8. #8

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    Re: Repairing a cursed Polaroid 8x10 processor

    Quote Originally Posted by Havoc View Post
    That's not a capacitor but a varistor. It's used as a overvoltage protection. So if the circuit was for 110V and they put 230V on it, then it is logical they are defect. You should change them both.

    The "241" would be the voltage rating which is 150VAC for a "241" so typical for 110VAC circuit protection. Get one with the same or slightly larger size because the size is what determines their power adsorbing capacity.

    But if that component was blown that others might as well be defective.
    Thank you, that is very insightful. I think though that the varistor burning out is my doing earlier today: I'm quite sure it looked fine before I plugged it in. While the person I bought it from did plug it in 230V mains, I think all that did was blow the fuse out which I replaced today. Is there anything else that could be wrong, or should replacing the two varistors be sufficient to get the darn thing working again?

  9. #9

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    Re: Repairing a cursed Polaroid 8x10 processor

    A varistor is a protection decvice. When the voltage goes above its rating, the resistance drops and it becomes almost a short circuit. Something like a "large" varistor can dump about 10000 A for something like 10 s for a few times. So its function is to draw so much current that the fuse certainly blows. Now there is a limit on how often it can do that. After a few times (and that is a few, not tens) it becomes defective. That's what you have now, the varistor is in a state where it conducts permanently so it heats and smokes. You really need to replace it before you can go any further. And for the price they cost, you better replace both. You cannot tell from the outside how the inside is.

    Problem with varistors is that they have a rather high voltage across them when they go into protection mode. So you need to be very careful when proceding. It would be helpful to have a schematic to tell you which components might be compromised.
    Expert in non-working solutions.

  10. #10

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    Re: Repairing a cursed Polaroid 8x10 processor

    Quote Originally Posted by Havoc View Post
    A varistor is a protection decvice. When the voltage goes above its rating, the resistance drops and it becomes almost a short circuit. Something like a "large" varistor can dump about 10000 A for something like 10 s for a few times. So its function is to draw so much current that the fuse certainly blows. Now there is a limit on how often it can do that. After a few times (and that is a few, not tens) it becomes defective. That's what you have now, the varistor is in a state where it conducts permanently so it heats and smokes. You really need to replace it before you can go any further. And for the price they cost, you better replace both. You cannot tell from the outside how the inside is.

    Problem with varistors is that they have a rather high voltage across them when they go into protection mode. So you need to be very careful when proceding. It would be helpful to have a schematic to tell you which components might be compromised.
    So does that mean the varistor may have been destroyed (even though it still looked fine) before the fuse blew when the previous owner put 220V on it? When you say they have high voltage when they go into protection mode, you mean they still hold a charge and I should be careful not to short out the pins as that will make it discharge?

    I'm afraid I don't have a schematic, I've looked around for a service manual but had no luck in finding it. If the varistor blows, are there other components at risk? Don't they remain protected until both of the varistors have blown? If not, how should I go about sourcing the components that may need replacement?

    I've included a more detailed picture of the main board and the relay board, maybe that helps a bit. I assume the only things that may need replacement are the capacitors? Or could something like the transformer be bust as well?

    Thanks again for the help, I very much appreciate it.

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