testing an s8550 transistor

[silly sausage]

i am trying to do a quick test of a sot 23 s8550 pnp transistor on a dead litokala lii500 charger using my fluke on diode check mode, with the neg probe to base and pos to collector i get no reading,if i reverse the leads i get base-emitter 0.704v drop and base to collector i get 0.702v drop,I a am trying to test q27 as in this vid, I dont understand russian or whatever he is speaking tho , Is it dead or am i testing it wrong?

[janoc]

Maybe learn about punctuation first. That word salad with no punctuation, no capital letters at the start of sentences, etc. that you wrote is incredibly difficult to understand.

Are you measuring this in-circuit? If yes, don't. Desolder the transistor.  In-circuit measurements are meaningless unless you 100% understand the surrounding circuitry and can be sure there is nothing in parallel that will affect the reading.

If those measurements are out of circuit then you are most likely doing something wrong:

- Do you have the pinout correct?

- Is that really S8550 and not e.g. S8050? That one is NPN and those measurements would make perfect sense for an NPN transistor.

I have never seen a dead BJT transistor that would show reasonable diode drop on base-emitter and base-collector junctions. BJTs fail most often completely short or sometimes open. But if both junctions show reasonable diode drops (0.7V is about right for a silicon transistor/diode) then the transistor is very unlikely to be bad.

[Jwillis]

You can set the YouTube video to auto translate for the CC(Closed Captions) in the settings. In Settings (The Gear) Click on Subtitles/CC, click Auto-translate and chose your language.

The video states that the Y1 transistor in question is a MBT8050 NPN. https://www.s-manuals.com/pdf/datasheet/s/s/ss8050_galaxy.pdf. He did not have the MBT8050, so he replaced it with a MBT2222 NPN. He later calls it a 8550 which is a PNP, https://www.mouser.com/datasheet/2/149/SS8550-118608.pdf, that he replaced with the 2222. The MBT2222 did not supply enough current so he replaces again with a TO92 8550.  This makes no sense.  Making code for the MBT8550 is Y2 https://file.elecfans.com/web2/M00/64/43/pYYBAGMERKWABWMHABkK9bSKvGw303.pdf