[R-390] R-392

[Jim Haynes]

On Fri, 24 Jan 2014, Johnsay Johnsay wrote:

> The 26A7 has always been the fly in the ointment with the R-392.  A 16 
> I'd be willing to play around 
> with mods though.  I have a couple R-392's and a free standing audio 
> module.

I will point out here that the Sunair DSB-900 quasi-military transceiver
uses an automotive-type audio amplifier to drive the little built-in 
speaker and to me the intelligibility seems excellent.

I should say they misuse it - the original part is rated for a maximum
of 26 volts supply voltage and they run it from 28V using four series
silicon diode drops, which is hardly enough.  That part is no longer
available (except from some ebay vendors in England) so when mine blew out
I replaced it with a present-day part of the same genre, but one with
different pin connections and a maximum voltage of 18 or so.  So I used
a Zener diode to get a propert voltage drop from the 28V supply.  And
because the pin connections are all different it is quite ugly, but at
least it is out of sight.  The original part was a UA783.  The replacement
I used is a TDA2003.