G'day Bob,



03 Feb 97 09:10, Bob Lawrence wrote to Roy Mcneill:



 BL>   He, he. I'm not fazed by that. I've designed sets with inherent

 BL> faults that no tech *ever* found. A tech's approach is to keep things

 BL> working; an engineer's approach is to make things fail.



You didn't happen to work for Akai by any chance? 



 RM>> I've seen amplifiers of all sorts take off, and the problem is

 RM>> either poor design (read: layout)



 BL>   I see. I've just told you that it is *never* (read: never) layout,

 BL> based on extensive actual design experience of these things and you

 BL> choose to contradict me. Okay



I realise that this is slightly different to the audio amps under

discussion, and correct me if I'm wrong, but don't many HF circuits

actually use the PCB tracks themselves as part of a resonant circuit?



Surely layout would then be very important for stability.



 BL>   I supppose you've confirmed this by fixing an oscillating amp or

 BL> DC-DC converter by changing the layout, and then changed the layout

 BL> of a good one to make it oscillate? Pig's arse, you have!



I haven't, but I'm a service tech, not a design engineer. I just fix

whats there, rather than redesigning things and changing the layout.



 BL>   I don't think you understand design. If I put a design into

 BL> production (read: that thing you have *no* experience of) and it

 BL> fails, there is a sudden stockpile of 100,000 repairs! Therefore, I



Sounds like Akai to me. 



 BL> can spend 200 hours (read: $24,000) making sure none of these things

 BL> happen... and I do. Engineers don't just get one working, we get them

 BL> *all* working, and to do this requires a rather deeper knowledge than



Tell that to Akai.



 BL>   Service techs just slap on a 0.01 and hope for the best - if you

 BL> can't fix it, modify it - and never find the real reason, never



Crap...  This is what failed engineers do when asked to service/repair

something that has broken down. Service techs fix the fault.



 BL> as actual fact. You don't have to do any more. Most of the time, all

 BL> you guys have to do is fix something that an engineer designed right,



That's the theory, but surely you are not implying that everything

designed by an engineer is flawless or couldn't be improved upon?



 BL> and when you find a bad one you use standard cures... slap a 0.01

 BL> across the collector base (0.01 is bit high, btw).



Crap. I've repaired zillions of electronic faults, and not once have I

needed to shonk a repair by redesigning the circuit...  the exceptions

being to perform 'standard modifications' from manufacturers

fault/data sheets.  The only service techs that I've known that have

tried to fix a fault be redesigning the circuit have been failed

engineers...  I used to get quite a laugh from one such chap that

forever insisted that an existing circuit "could never work in its

current design" --  in spite of the fact that the same make/model

machines obviously DID work.



 BL>   Unfortunately, design engineers can't work like that. We have all

 BL> the time in the world to get it right. I offered you a little of that



Pity that more of them don't actually use this time then. Even a lowly

service tech like myself could do better than some of the designs I've

seen  :-(



Cheers,

Rod



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