Yet another AC/DC adaptor, not those China made but this one from Finland

[BravoV]

Many households must have tons of these small AC/DC for cellphone chargers lying around, just found out my old Ericsson cellphone charger from mid 90's I guess, and it is badly crushed and cracked while at the bottom pile of unused electronic junks. 

I'm aware there are many of these AC to DC adaptor teardown/discussion threads in this forum, quite boring since almost all are ended up bashing the low quality stuffs made in China, then I thought why not post yet another one but this time made in Finland. 

Comments :

- Designed with fully discrete components based, no custom switching chip, the only ic is LM358 soic op-amp at secondary side.
- All bottom PCB components have those tiny "glue" spots oozed out at their side, its to hold them when in solder bath, just watch closely at the close up shots.
- All electrolyte caps are quality caps made in Japan by Nippon Chemi Con with KMG type.

And yes, its still fully working fine with good regulation and as expected with pretty good ripple too. 


OK, I will just let the attached photos below to speak for it self.


Enjoy.

[lapm]

From time when engineers in Finland were still worth something. Since then goverment nerfed education system big time...  Sadly i was in school at time that nerfing hit. More byrocracy, less teaching.

[BravoV]

From time when engineers in Finland were still worth something. Since then goverment nerfed education system big time...  Sadly i was in school at time that nerfing hit. More byrocracy, less teaching.

I can see you're from Finland, I guess seeing this thing must generated quite some feeling.

Btw, when was that "education nerfing" era started ? 

[akis]

How big/small is that thing? "7.6V/600mA" that is around 5W at the output so say a 7W mains transformer would suffice. You'd need a 7W transformer, a bridge,  one electrolytic cap, an LM317 type of regulator maybe on which you'd drop 1.5V (so make the transformer 9W for good measure), two resistors and an extra electrolytic cap at the output. You'd have a dead simple circuit, cleaner output, no parasitic switching frequencies, and it'd work forever.

As a matter of fact that is exactly how I built a 2A/5V transformer to power my wireless access point which is in the loft and which had thus far destroyed two brand new AC/DC adapters those funky SM types because of the temperature range in the loft I guess. Probably in its 4th/5th year now working great up there (touches wood).

[amyk]

Besides the capacitors, this one also has an inductor on the output which is probably what reduces the ripple a lot; the cheaper ones often omit it.

[daijo]

Just FYI, the text "ENDAST FÖR KONTORSMASKINER" is Swedish and translates to "FOR OFFICE EQUIPMENT ONLY".