[sdiy] CA3046 Heater / Substrate Question

Nils Pipenbrinck n.pipenbrinck at hilbert-space.de
Thu May 5 21:40:53 CEST 2016

On 05/05/2016 09:13 PM, ASSI wrote:
> On Thursday 05 May 2016, 21:06:21, ASSI wrote:
>> as all the current will flow through Q1 - R3 - R4 - R6 anyway the way you
> Make that Q2  - R3 - R4 - R6, sorry for the typo.

Hi Achim,

I doubt this is the reason. I replaced Q2 by a non-array transistor 
(2N3904) and all the strange behaviour just goes away.

Obviously the isolated Q2 doesn't help the heating, but the electrical 
difference between the array transistor and the 2N3904 that I've used is 
the common substrate. Not much more.

So I'm pretty sure the substrate plays some role somehow. That said, I 
have no idea which of my power supply lines comes up earlier. Could I 
run into some kind of latch-up here?


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