Problem with ca3140s (Developing the Light Metal ring mod)

[RaceDriver205]

I have been developing the PCB for the Penfold "light metal" Active Ring Mod for sometime now, and I have managed to trace the PCB from the layout on the ancient document.

I have built it - but of course it is not working. Using my universitys Signal generators and CROs (yes, uni is good for something), i have isolated the problem down to this:

The CA3140s are not working for some reason. I have an image showing the issue at this address:
http://www.tothemax.web1000.com/acringproblem.html

In the second example, there should be a sinewave output at the C4/R9 junction (ran circuit in a simulator).

Any help would be appreciated (and a solution would mean a new Effect for everyone)  . Cheers.

[Mark Hammer]

1) You do know these chips are as static sensitive as CMOS, right?

2) If you are using the metal can version, you may well experience some of the same problems with getting good chip-pin to socket-contact connection as I have had in past.  Bending those 8 wire legs of the CA3140 to sit just right in an 8-pin DIP socket is no easy mater.  probaly a good circumstance to use machined sockets....if you are not already doing so.

[soggybag]

Right on! I have been wanting to build this for a long time. I traces everything out and redrew it to fit on the perfboard sold by Futurlec. But I have yet to build it. It is sitting in a ziplock bag of parts waiting for some free time.

[Unbeliever]

I can't tell from the circuit snippet, but likely you can use another op-amp that'll work just as well AND won't blow up as easily - an LF351 would make a good first 'sub'.

[RaceDriver205]

I did realise that the chips are static sensitive, AFTER i put them in (using dip ics). I am now thinking the explanation is that I blew both of them, but ive installed a lot of cmos chips before and never blown one. Are there any equivalent op-amps that can be used in its place, as penfold said he chose the ca3140 for special reasons?

Thankyou all for your interest.

[Unbeliever]

Didn't I just answer that?

http://home.att.net/~synthsource/ens76/vco4.htm

If LF351s are a sub for CA3140s in a precision oscillator, you can be pretty sure they're a good sub everywhere else too. Considering what you have isn't actually working at all, there's nothing lost by tossing any opamp you have at hand in - at least then you can see if you're getting some signal through!

[RaceDriver205]

The LF351 is the same as the TL071 JFET opamp, but the ca3140 is a cmos opamp. Hence I was hesitant at such a substitution, as they are not equal. However, I will make the substitution and see if this changes the operation, as I am a believer in 'shoot now ask later'.

[StephenGiles]

I think Uncle Penfold had good reason for specifying the CA3140 in this project.

[RaceDriver205]

Tried the lf351 and didnt work. Cant use sig. gen. + CRO to check the output until I go back to uni (we have a 'massive' 1 week holiday  , whatever happened to good old 3 weeks). I think I need to get some more ca3140, and attempt maximum static awareness.
Dont worry people, I wont give up!