Monday, April 18, 2016

occasional RF Amp test

... converting the X-tal oscillator to RF 1

capabilities test with my "phase shift std." phase shifter

 ◄ works quite occasionally e.g. returns ~Max. performance although using a different amp. may reach or exceed the unity gain fq. . . . (funny i guess i already uploaded ↓that↓ stuff - must´ve been in prev v. of this blog , ?hmm) anyway here´s how to exceed the transistors unity gain ::

(spice magic)


Wednesday, April 6, 2016

a fuzzy science on old transformers 2

finding the optimum simple design for 9V linear adapter

using std. parts 7805 , TL431

the load peak/-step response is somewhat unexpected here

using low ß , high power switch (such as *MJE13003)

the load regulation stays below acceptable

using bridged LM78L05 and LM324

fine tuning the bridge may induce better results this 1 however won´t pass because it´s load response

same as above with an attempt to add a reference to be used in better line rejection ...

... can´t gain steady reference - won´t test all possible situations for such a noisy one = reference failure , halt, halt

using low ß , high power switch* and random intuitive design

looks pass - tough i don´t know about higher frequency load responce


Sunday, April 3, 2016

a fuzzy science on old transformers

By the time it's gathered here a pile of transformers from the PC speakers , cordless & cell-phone loaders , modems , routers , X-mas lights , e.c. - some of which have their primary's overheating/over-current protections blown , for some i have replaced the 2-ry multiple or too low voltage windings with a single new 1 ...

the following table is apx. accurate within (more...less) ±...25...33... % which i find sufficient describing the multitude of transformers from different manufacturers and possible evolved...recovered fault conditions

the fuzzy science :: we find -
the lab./stat. avg. impedance of the 1-ry winding (2-ry open = apx.1MΩ(Vm))
the lab./stat. avg. voltage transfer ratio (2-ry open = apx.1MΩ(Vm))
the output voltage mutiplier for the rectified 2-ry voltage (2-ry open = apx.1MΩ(Vm))
the output voltage degrading coefficient for the rectified 2-ry voltage with load (25...330 Ω , 47uF filter)
the estimate (based on above) for 1...10k Ω loading of the rectified , filtered output (on the 2-ry winding)

so the table list below rectified , filtered DC voltage values estimates against the load resistance :
the percentage (parenthed) = P.OUT / (P.IN - P.OUT) @ est.-d  P.OUT.Max

the .CC is operational Nokia (Type: ACP-7E) 3.7V cellphone charger´s TF
.C10 is ® while .C60 , .C70 and .230 have the replaced 2-ries
.ZHN28 is from the incandescent X-mas lights rectifier from China