Electronic Load 300W - June 1990 - Questions

[Guest]

I want to build an electronic load for testing PSUs. I came across the Elektor one from June 1990 which goes to 300 Watts. It seems good enough for what I need, and is fairly simple and cheap.

However, there seems to be some discrepancy over parts used.
Transistors T1 and T2 are specified as BC239C in the schematic but are not listed in the parts list. Also worth noting is that the BC239C is in a TO-92 package while the PCB layout shows a TO-220 footprint.

A TO-220 seems to make more sense since each transistor has to supply the base current to 5x 2N3055s, which at worst case will need 100mA each.


I assume this error was mentioned in the 1990 July\August issue under corrections and updates, but I do not have the paper magazines from 1990 - only the 1990-1999 Archive DVD and PDF files, and this only includes articles and not the errata\corrections listings!!

Can anyone who has the real elektor magazine on paper tell me if there was an update posted there to clear up this confusion, or if someone can give me advice regardless? Thanks

[Elektor Editor]

Try BD239C

Jan

[Guest]

Ahh of course, now it makes sense. Thank you!

I was also wondering about the value of the 5 Watt resistors - they are referred to as both 0.22 Ohm and 0.33 Ohm. Which one is correct?