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I'm fixing a device that is using this S81250HG voltage regulator that takes 9V as input and has an output of 5V. But this regulator seems to be fried. I'm measuring and it gets 9V on the input but nothing on the output. But I don't have the same model to replace it and see if that is the only problem.

However, I have lying around a 5V voltage regulator: L7805CV. For what I see it can also take 9V and regulated it down to 5V and it has 3 pins too (even though they don't have the same distribution, but I wouldn't connect straight to the PCB).

I was wondering if I could use this L7805CV voltage regulator as an alternative to the S81250HG or it could cause any issues. At least to see if the device turns on. And then I would look for a proper replacement.

Updating with a some more information:

The device I'm fixing is a Sony Discman D-50 (D-5 in the US). Here you can find a copy of the service manual.

If you check on page 17 of this document you can see the part of the DC input and voltage regulator: enter image description here

And also on page 26: enter image description here

Thanks!

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  • \$\begingroup\$ It looks like it should work but, there may e subtleties about the usage of the original device that might cause a 7805 not to produce the right output. Show your schematic in other words. \$\endgroup\$
    – Andy aka
    Commented Jan 29, 2021 at 11:33
  • \$\begingroup\$ Thanks @Andyaka. I've updated the question adding this information :) \$\endgroup\$
    – JV Lobo
    Commented Jan 29, 2021 at 11:53
  • \$\begingroup\$ It looks like it should be OK. \$\endgroup\$
    – Andy aka
    Commented Jan 29, 2021 at 11:56
  • \$\begingroup\$ Thanks a lot :) Feel free to add your answer so I can mark it as valid for my question. \$\endgroup\$
    – JV Lobo
    Commented Jan 29, 2021 at 11:58

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Given that the 7805 is a bit more powerful than the original device AND there doesn't appear to be problems with low-drop-out in this application, the 7805 should be a good temporary substitute to prove the point: -

At least to see if the device turns on. And then I would look for a proper replacement.

It may prove to be a bit noisier than the original so that is something that might put you off making it a permanent replacement. Also, the 7805 does appear to be more hungry in terms of quiescent current so, if the unit is battery powered this may also cause a problem. I couldn't check that because the link to the product is faulty.

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    \$\begingroup\$ Thanks for your help Andy :) The device only uses a power adaptor, no batteries involved. \$\endgroup\$
    – JV Lobo
    Commented Jan 29, 2021 at 12:03

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