Re: 556 problems

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Fucian-at-aol-dot-com>

In a message dated 2/10/02 2:24:56 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

<< Matt
 
 Check Jan Wagner's site concerning 555/556 drivers for SSTC.
 
  http://www.hut.fi/~jwagner/tesla/SSTC/results-and-progress.htm
 
 Make sure your reset line is hard tied to Vcc, or if you are gating
 you will need a pull up resistor in the 1 - 10K ohm range to reset pin.
 Pull reset low to disable output, and reset does have priority function
 in 555 chips. Also, bypass the control voltage pin with a 0.01uF cap
 to (-) of dc power.
 
 The minimal part count comment concerns me some.  Watch your
 frequency pots between DC and discharge, and discharge and trigger/
 threshold pins.  A minimal resistance (1/10 of pot value) should be
 placed in series with pot to prevent the pot wiper setting input
 resistance to 0 to discharge (I've made same mistake and killed the
 oscillator and the chip).  I am confident that there is a wiring problem.
 
 If the circuit frequencies are less then 1Mhz
 and the circuit works on a breadboard, the only reason it won't
 work on a hard wired circuit is defective chips, wire placement,
 insufficient bypass caps, or a wiring problems.  There is a physical
 reason why the circuit isn't working.  I would physically build circuit
 on both breadboard and circuit board.  Get breadboard working
 and then physically ohm out each wire.  It will take about 2-3 hours,
 you'll learn alot, and there will be something missing.
 
 Regards
 Dave Sharpe, TCBOR
 Chesterfield, VA. USA >>
I am using a circuit just like Jan's except i have a 556.I have decided to 
look for some small copper clad PCB and etch a circuit.I am tired of the 
little protoboard.The circuit frequency is around 450khtz.It seems that when 
i wire the staccato part into the main timer, it lowers the voltage.This only 
happens whne on the solder protoboard.I am going to try one more time and 
REALLY look hard to see if maybe a wire doesnt solder just right or something.

Matt