Re: SSTC-556 timer IC malfunction

["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 1/15/02 5:17:19 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

<< > Hi, i just recently used a staccato design with the 556CMOS IC.I was 
doing 
 > pretty good for being me.Once i added a MOV across the primary, the 
staccato 
 > just failed immediatley.WHY?
 
 don't change a running system! ;o) (ok why it actually failed, I can't
 tell... just bad luck maybe... :)
 
 > The funny thing is that it still is pulsing.At 
 > the wrong frequency of coarse but it wont respond to POT adjustment.
 
 ah ok. Well, shielding the drive circuit won't help the 556 any more. It
 probably is half dead already. So why not plug in a new one, AND
 use shielding? check if that helps. 
 
 > get a sizzle out of an ignition coil.What could be happening?Also
 everytime i 
 > try using a totem pole transistor arangement with a 2N3904 and 2N3906, the 
 > output voltage drops to about 7volts.WHY?
 
 Did you hook up the totem pole right? I.e. NPN is above and PNP
 is below? Emitters together? 
 (More correctly, "complementary emitter follower". A "totem pole"
 is something different. But I, and others, always say totem pole, 
 when we really do mean a compl. emitter follower... ah why bother...)
 
 Output voltage won't be exactly 0V and 12V. You may end up with 0.5V and
 11.5V, which is due to V_base_emitter of the transistors (depends on
 transistor).
 
 How and where did you measure 7V, by the way? An oscilloscope would be
 best in this case, because cheap digital multimetres don't seem to work
 well at AC above a few kHz, even if the maybe built-in frequency
 counter/freq display does work
 
 If you have a resistor to the mosfet gate, and you measured the 7V max
 peaks directly at the gate, this would mean that the gate resistor is too
 large. So place a second resistor in parallel with it to get resistance
 down. (or exchange with one smaller but higher wattage resistor)
 Did this help?
 
 cheers,
  - Jan
  >>
Hi, 
Yes i belive the totem pole is in the right order.I dont have ANY resistor 
going to their base.I measured voltage from the emitters.I used to get the 
correct output with 547's and 557's.I will try them. I am waiting on a 
shipment of 556's right now. I belive the totem pole is correct because i 
tried reversing the transistors and got like 1 volt before it BLEW up 
LOL!!!!!!!!!!!

I will make a enclosure with Al foil for the circuit.Where do i ground the 
enclosure?Common ground or the secondaries ground?

The staccato is pretty cool! Its neat to watch the output change so 
dramatically!

Matt