UniVibe/NeoVibe again

[Aharon]

Checking both I see the MAillet version has a darlington lamp driver and the RG version doesn't.Could that account for the problems,should it be a darlington pair?.
Second,RG and Maillet state the lamp should be a 12V/25mA RS type and then Maillet changes that to 1.5V/25mA in his "lamp driver"mod schem.
Which one is it?
Thanks
Aharon

http://www.lynx.bc.ca/~jc/UnivibeCloneDrvrMod.gif

[R.G.]

the MAillet version has a darlington lamp driver and the RG version doesn't.Could that account for the problems,should it be a darlington pair?.

The original univibe, and by extension the Neovibe is non-darlington. Many Neovibes, and *all* univibes use non-darlington. The darlington setup is something JC cooked up to try to improve the performance of the lamp driver. So, no, not having the lamp driver be darlington is not "the" problem. Having a darlington there is one way to make the design more tolerant of parts there, though.

Second,RG and Maillet state the lamp should be a 12V/25mA RS type and then Maillet changes that to 1.5V/25mA in his "lamp driver"mod schem.
Which one is it?

It isn't either. The voltage doesn't make much difference. The current rating does. However...

A 12V/0.025A bulb has a working resistance which requires 12V to make the 25ma flow. The 1.5V/0.025A bulb has a lower resistance, so that it gets to full current at only 1.5V across it. That lower voltage means that the driver transistor has to soak up the remainder of the supply voltage. That means that the driver transistor gets hotter with the 1.5V bulb than it does the 12V bulb. It also means that the voltage gain in the driver **can't** be as large, because it's more heavily loaded. That's likely to be the reason JC's version needs a darlington - just a guess.

The Neovibe works as shown; it's the original univibe setup, with all its warts (except for the power supply regulator - I couldn't help myself there.)

[Aharon]

Thanks for clearing that up RG.
I know sometimes one gets caught up in other peoples build bugs that have nothing to do with the PCB design or the projects correctness but  it's good to  get the lowdown from the horse's mouth so to speak.
Great
Thanks.
Aharon