Polar EM WSP memory bank

Discussion in 'Cutters and Trimmers' started by Waqas_zahid, Oct 15, 2021.

  1. Waqas_zahid

    Waqas_zahid Senior Member

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    Hi,

    The old EM polars have a WSP memory bank that ER-3400 EAROM chips for data storage, these chips aren't easy to find now and a replacement board is quite expensive, I was wondering if anyone has worked out a modern replacement for these chips? At the end of the day these are 1024 word x4 bit memory chips with unusual voltage requirements?

    I am thinking may be I can build an adapter and use a battery backed SRAM on a board that would just plug onto the EAROM socket, I can ignore the -12V and -30V voltages entirely.
     
  2. CHOCK

    CHOCK Senior Member

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    Hi Waqas;

    Yes you can do it, with the same characteristic, and build adapter and use the battery backed SRAM.

    Ignore the -12 -30Vdc. but is Important the Characteristic of EAROM chips.

     
  3. Waqas_zahid

    Waqas_zahid Senior Member

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    Hi Chock,

    Thanks for the response, I am looking at the 2114 SRAM, do you think this can match the 3400's in term of characteristics?
     
  4. Mathew

    Mathew Senior Member

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    Hello Waqas,
    You are right, these chips are obsolete and not available anymore. I purchased 20 pcs 12 years ago and still have some new. As Chock explained, you can reset them BUT quite difficult. There is also another solution that you erased the entire memory bank while it is mounted on the machine. How many memory sections are damaged? I can't remember exactly the command, but try P- plus P+ and Delete bottom or S- plus S+ and Delete bottom. I hope it works.
     
  5. CHOCK

    CHOCK Senior Member

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    You must look carefully, the Characteristic, in Data Sheet, from manufacturer.
    Blessing
     
  6. Waqas_zahid

    Waqas_zahid Senior Member

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    Hi Mathew,

    When I turn on the machine I see -- -- on the program seven segment display, pressing the delete button brings the display to 1 0 but whenever I try to save a program I see error 69. The customer gave away this board for repairs and called me in when the board didn't work, when I opened and inspected the board I found out one complete row of ROM chips were plugged in the wrong way so I can can't say for sure if any of the chips are functional now.
     
  7. Waqas_zahid

    Waqas_zahid Senior Member

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    Hi Chock, I already have it seems this might work, I was just looking for another opinion
     
  8. Mathew

    Mathew Senior Member

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    Hi Waqas,
    When it shows -- -- on seven segment, then the memory bank is not accessible. Take out the row which were installed wrongly. Then insert the rest in an order. Make a reset and test. You might be able to write and read a part of the memory. For example you can see memory from 1 to 40. Machine should be able to read at least a part of memory. If it is inaccessible, then check EI module.
     
  9. Waqas_zahid

    Waqas_zahid Senior Member

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    Hi Mathew,

    I made all possible combinations of two chips at a time on the board, when the machine is powered up I -- -- on the display and upon hitting delete I can see 1 and 0 pressing the P+ and P- button I can scroll through numbers upto 99, what does this signify? But when ever I try to save a program it gives the 69 error, I tried randomly saving to some other slots but it showed this error, one rare occasions when I power up the machine I see 1 0 and not -- -- on program display but it fails to write, I did check a couple of chips ok the EI board namely the 74245 as it was getting slightly hot but seems like this is normal and then the 138s as they are used for chip select, I am not exactly sure if the I/O peripheral chip on the EI itself is defective, what do you think the problem could be based on the above observations?
     
  10. Mathew

    Mathew Senior Member

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    Hi,
    When the machine is Switched ON, it reads the last program before the power cut OFF. If you see -- -- on both seven segments, it means control system recognise and error with memory bank.
    By press P+ and P- can let you to scroll the memory bank and it doesn't mean that you are reading the memory. Error 69 significantly means no access to memory bank. There are few remedies for this error:
    - Low supply voltage on EI.
    - Connection between EI and base plate (harness cable).
    - Memory bank itself.
    Back to your explanations:
    It's so often that 74244 or 74245 getting slightly hot particularly if they are TTL chip not CMOS. And it is same for 74138. I've replaced 82C55 Peripheral chip many times on IAR and AR modules. Replace this chip and try to find the replacement from NEC uPD71055, it's much better than its ancestor.
    At the end, check the modules on another machine. You will not ruin anything, I promise
    Good luck
     
  11. Waqas_zahid

    Waqas_zahid Senior Member

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    Hi Mathew,

    Thanks for the detailed response, I verified voltages and they measured out well within tolerance, plus no LEDs for low voltages were ON on the EI board so that was a good sign.

    To be honest the fact that 8255 could be faulty didn't occur to me but I think there is no harm in replacing it and is something I could do. I also thought that pressing the P+ and P- isnt letting me scroll through the program actually and by probably pressing the save button it tries to write and the read back the data and since it cannot verify the data so that results in an error, I will replace the 8255 and report back, thanks for the help!
     

  12. Waqas_zahid

    Waqas_zahid Senior Member

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    Hi Mathew,

    Replacing the 8255 makes no difference cannot access the memory and the machine starts with a -- --, I will have to look at the WSP now.

    The situation is same as before, same behavior and errors.
     
    Last edited: Oct 20, 2021
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