Oh! Ok...well since you asked...
The "parings" are more of the situation than to simply drop in parts because they fit and the pin out works.
Well, if that doing your own thing - was the case, we'd have a lot of radios using the 2SA473 instead of the 2SA1012. Cheaper and still available seems to have similar ratings but not by the LOADING response they exhibit.
There's always a catch...
Once you'll use it knowing what the radio did BEFORE you swapped that part - you'd be back at his bench demanding to restore the radio back to OEM or getting your money back for the crappy performance the new upgrade does...
Not just because of the main current load part used, but the complimentary driver used with it. The best performance comes from mating the right parts to better the two - for they become more than the Sum of their parts.
The 2SA473 stands alone now, but the 2SA1012 used 2SB525's in Uniden's and Cobra and in the Galaxy line - they wanted to beat that - but had chassis' that used 2 Bipolar Finals - Current Munchers.
- - literally quadrupling the power demands but they needed to use a higher current DRIVER part to offset the current flow "backdraft" the 2SB754 exhibited
- When you use heavy current loading and try to make it analog one of the dynamics is how the intrinsic doping and layering of the die design the main part has - affects how it reacts under such loads - mostly an unknown reactive current draw. IF the substrate was "slow" to load up with electrons transferring their power to the next region - it's a loss in both transfer and heat generated is increased.
- - it had a high-frequency roll-off effect which if you wanted a few more watts - you'd turn up the AM power but then you ran into the "holding up the voltage but losing the Current draw" - in the process - process - it didn't hold up as well in bandwidth products - everything shifted more to DC. A nonlinear action..
- - when you started to overmodulate - this SATURATED the part - ruining the nicer crisp output and bandwidth it could do when the power trimming was set to stock or slightly less (current demand)
- - that is where the 2SA473 came in. They wanted heavier current power - just not voltage swings to apply/supplant the power losses across the parts junction.
- The higher current offset to voltage rise is one of many keys in designing this type of Darlington and making it work right. You need to know the intrinsic losses (impedance losses as ohmic effects of rise of slope to gain or HFE) You want Current and Voltage yes, but you want Current to MATCH the losses thru the widely varying power dynamics of the load this design sees.
- So they used a part that isn't the best at voltage gains but did have a good current transfer characteristic.
- And if you swapped that 473 out with another NTE part - you actually had better slew/skew rates for asymmetry - you didn't "mush" as bad as if you kept the OEM parts in place.
There were several parings of simple parts that even when used in the RF Deck - (2086/2166 pairing) worked like champs - but you would not think of them as working pairs.
This was one of the many conversations I had PM-wise with such people that now claim what they do about the "Maxi mod". IHMO to me it's just another tampon that is being used to staunch the flow of bettering the bleed over tripe we have to fix when something the operator does - goes wrong - in doing so - generates a Toxic-Shock environment that really makes matters worse and does not fix the problem - only generates another avenue of revenue for those wishing to exploit it.
You did ask...
As far as the "Jawa" spotting - I only have sad news - a legacy has ended - and I'd rather tell the story around this, at a later time.
