[sdiy] AN299 and all that !

Pete G. peteveg at hotmail.com
Wed Jun 12 14:50:04 CEST 2002




>From: "Tony Allgood" <oakley at techrepairs.freeserve.co.uk>
>Reply-To: "Tony Allgood" <oakley at techrepairs.freeserve.co.uk>
>To: <synth-diy at dropmix.xs4all.nl>
>Subject: Re: [sdiy] AN299 and all that !
>Date: Wed, 12 Jun 2002 09:25:29 +0100
>
> >Anyone remember a Babani book of sysnthesiser projects from about 20
>years ago by a certain M.K Berry ?
>
>I bought this one at the Breadboard show of 1981. It probably taught me
>more about electronics than any other book. Mainly because all the
>designs suck big time, and you then have to find out how to make them
>better. And why did he not put a single filter of any kind in the damn
>book?

Yes Tony, my recollections too !. I remember how I spent an entire summer 
holiday in my Dad’s garage trying to get the one of the two VCO circuits 
(not the 8038 one) to work. Needless to say, it was an entire summer wasted 
– nothing even whistled !. At the time I had very little technical 
appreciation of op-amps & transistor circuits , and no ‘scope so there was 
little chance of debugging the thing. Looking at the schematic , as I did 
recently , really makes you laugh (or cry !) – IIRC there is no way the 
thing will ever oscillate & even if it did  the correlation  between input 
voltage & output frequency would be very weird indeed !. At the time, I even 
wrote via the publishers to Mr Berry, explaining that I had attended to the 
PCB foil errors (of which there were many !) and asking for any further 
advice – some months later I received a letter in which he suggested that I 
apply a –ve control voltage to the base of the input of the (NPN) transistor 
to ‘see if that worked’ !. Unfortunately I don’t think I kept the reply !.

The serious point is that this kind of episode could easily put you off 
electronics for the rest of your life – when you’re a kid building circuits 
from a book published by a reasonably credible publisher , when things don’t 
work you assume its you that is at fault – not that the guy who wrote the 
stuff is basically a clueless idiot trying to make a quick buck.

I recently discovered that a synth-mad colleague of mine also had a copy of 
the same book when he was in his teens. He built the sound generator circuit 
in Chapter 1 (based on the Texas SN74189 ?? – the of  Computer Battleships 
fame !). Needless to say it didn’t work – the chip just got hot !. The 
solution in his case was simple – the board got taken into the back garden 
and ‘adjusted’ with the ball-end of hammer !!

Pete.

PS. Complements  on a really nice website !


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