(Topic ID: 211721)

LM741 in U9 that works for a Bally -32 sound board

By Joydivision

6 years ago



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    #1 6 years ago

    I had a problem with my -32 Bally sound board, after getting it working with changing a couple of parts it was very quiet with no volume adjustment. I swapped over a few other new LM741s (U9), no change.

    I read this post about the same problem & it turns out that unless you use a LM741 as per original manufacturer/date code, you need to do a mod.

    the mod is outlined here...

    https://pinside.com/pinball/forum/topic/volume-problem-after-replacing-u9-on-bally-32-sound-board

    The 741s I was using were UA741CN ics, they all didn't work. I got hold of some LM741CM chips, tried them & they all worked fine, volume adjustment was available as normal, so no need to do a mod in the end, these were also a later date code & readily available (08 date code).

    So it looks like at least some LM741CNs regardless of date will work & the UA741CNs won't work.

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    #2 6 years ago

    I don't think you will find any new make 741 that works in that board. I have tried LM741 by national and they didnt work. Where did you buy it at? I think TI bought national semiconductor in 2011... so 741 that work in the -32 are probably old stock.

    Download the Dolly Parton Manual and add the extra circuit on the 741 that isnt in the -32. Two 10k resistors dividing the 12v in half + a 1uF smooth cap. Not that bad of a job to fit the new parts. You can drill a few holes in the board.

    #3 6 years ago
    Quoted from barakandl:

    I don't think you will find any new make 741 that works in that board. I have tried LM741 by national and they didnt work. Where did you buy it at? I think TI bought national semiconductor in 2011... so 741 that work in the -32 are probably old stock.

    I bought them from an ebay seller, he only had 4 units. These look like they would be similar though, even an older date code, that is if they send the same ones in the pic, good old Polida...

    ebay.com link: 10PCS OP AMP IC NSC FAIRCHILD DIP 8 LM741CN LM741CN NOPB

    After I read somewhere where you worked out a late 70s 741 chip like the original was needed to work I tried to find some, the ebay seller I bought from had some national chips with an 80s date I thought I would try, he ended up sending me the 08 date ones instead which to my surprise worked.

    #4 6 years ago

    Not sure I would buy anything from or support Polida on ebay - they're one of the largest sources of counterfeits on ebay. Sounds like you got lucky, though.

    #5 6 years ago
    Quoted from Joydivision:

    I bought them from an ebay seller, he only had 4 units. These look like they would be similar though, even an older date code, that is if they send the same ones in the pic, good old Polida...
    ebay.com link » 10pcs Op Amp Ic Nsc Fairchild Dip 8 Lm741cn Lm741cn Nopb
    After I read somewhere where you worked out a late 70s 741 chip like the original was needed to work I tried to find some, the ebay seller I bought from had some national chips with an 80s date I thought I would try, he ended up sending me the 08 date ones instead which to my surprise worked.

    You likely got a remark from Polida. That means the pulled that chip off of an old PCB. Sanded down the top and put a new imprint on it. The picture even looks like they roughed up the top of that chip.

    GPE is a bit over dramatic about the Chinese resellers. In this situation getting an old remark was actually a good thing since you didnt have to mod the board. Have fun

    #6 6 years ago

    The lm741cm chips I bought were not from Polida nor a another chinese seller. There were only 4 only NOS chips that came from a reputable seller. I checked them with a 12x loupe, I can easily tell a remark used chip under magnification no matter how good it is.

    They were not used reblacked, restamped chips. The legs were also on the correct angles & had not been touched/sanded. They were genuine NOS chips. Not sure if the 08 is the actual manufacture date on these particular chips, or just part of the part number, if 08 is not the manufacture date, i'm assuming they were at least made in the late 1980s or later with that logo.

    I only mentioned the ones from Polida as they had a similar codes, but it wouldn't surprise me if Polida do remarks on cheap common chips as well as rare chips.

    #7 6 years ago
    Quoted from barakandl:

    You likely got a remark from Polida. That means the pulled that chip off of an old PCB. Sanded down the top and put a new imprint on it. The picture even looks like they roughed up the top of that chip.
    GPE is a bit over dramatic about the Chinese resellers. In this situation getting an old remark was actually a good thing since you didnt have to mod the board. Have fun

    And some people have no problems supporting those that are intentionally ripping off people.
    Remarks "ARE" counterfeits. They are intentionally deceiving the buyer into buying a part that is not the part it is advertised to be. That sounds like the perfect definition of "counterfeit" to me. If the part was the same part then why would they sand down the top, black top it and remark it?
    There is no over dramatics about chinese resellers of counterfeit parts. Simple - they are crooks, period. People that know they are crooks and still openly support the crooks with large component purchases of known fake parts to save money...
    If people would stop sending them money then we could stop this invasion.

    #8 6 years ago

    i ordered a LM741CN from Marco last november for a 2518-32. it worked fine.

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