MicrobeHunter.com Microscopy Forum

Hi all! The old power supply from the microscope is out of order. I decided to disassemble and fix it, as I understand a little about it. I tested and found that the BC547 transistor does not work. I looked for a replacement on the Internet and here https://chipdatasheet.com/transistor/bc ... ent-specs/ subtracted that the modern equivalent in terms of specs and BC547 pinout is BC550. I'm thinking of putting in a new one or looking for the same BC547.

alexgor26 wrote: ↑

Thu Jul 28, 2022 9:29 pm

the modern equivalent in terms of specs and BC547 pinout is BC550.
I'm thinking of putting in a new one or looking for the same BC547.

They are in the same family:
https://www.mouser.com/datasheet/2/308/ ... 310266.pdf

The BC547 tolerates a higher Emitter−Base Voltage (6V) than the BC550 (5V),
which may not matter in your application. The BC546 is more tolerant...
Small signal transistors typically do not fail unless something else provokes them,
e.g. a leaky capacitor.

I do not know where you are, but currently, TME has a tolerable few BC547 variants in stock. You may not even have to form the leads.

As a ham operator I can attest that electrolytic capacitors fail. Replace the capacitors

DrPhoxinus wrote: ↑

Fri Jul 29, 2022 6:12 am

As a ham operator I can attest that electrolytic capacitors fail. Replace the capacitors

Yes, generally the first to go in a power supply; and when one goes, others are probably not far behind. I like the screen proportions of my older Princeton monitor, so when one of the electrolytics failed a year ago, rather than tossing the monitor, I replaced all the electrolytic capacitors in its power supply circuit. Working fine since.