In order to repair this scale which wouldn't turn on after being supplied with power, I replaced two transistors.
The first transistor which I replaced was a BD 136 PNP transistor made by Motorola, which I replaced with a BD 140.
The second transistor which I replaced was a BC 846 A (marked 1As) NPN transistor made by Siemens.
I replaced it with a much more recent BCV47 NPN transistor that I had lying around and which had the same specifications.
The two transistor have probably been damaged because a wrong power supply has been used with this scale.
Although I controlled the output voltage of the power supply provided with the scale, when I plugged in the power supply the BD140 blew up.
When I used my lab bench power supply the scale worked correctly without any problem.
So I had to change the BD 136/BD 140 transistor a second time. I then decided to put this power supply aside and buy a new one.
| Product | Quantitiy | Price [€] |
|---|---|---|
| Sartorius PT600 scale (used) | 1 | 14,50 |
| BD 140 Transistor | 1 | 0,03 |
| 12V Power supply | 1 | 10 |
| BCV47 Transistor | 1 | Free |
| Total cost: | 24,53 |
