[sdiy] Re: EFM Vco4d? ( or even Vco4 E !!! )

[jays at aracnet.com]

I'm assuming that you are using the EFM circuit board.

I've built both the 4D and 4E. If all the mods (which are documented) are done right it should work. Only thing not in the docs is both need a pull up on the output of the pulse comparitor. I did not install the 'sync fets' but when not in use their gate should be grounded as mentioned by someone else.

I looked into all those extra holes on the 4E. I think if you trace them out they will form a heater to heat the CA3046 so the tempco is not needed (still need a 1k regular resistor in there though). This is another technique for getting temp stability in the VCO. Biggest problem is that the CA3046 runs hot and it will suck a lot more current. From what I've read heaters take 40ma-80ma of additional current.

So double check your work, get the ohm meter out and check connectivity, if you use sockets check those out, maybe swap some chips.

Jay S.


Peng <peng3002 at yahoo.com> wrote :

> I built the VCO4e about a year ago, but couldn't get it to work. Every two months or so I pull it out of the "modules to fix" box and try to get it oscillating but I've had no success ... yet. Though, I must admit, I haven't tried to breadboard it which is probably the best way to test/diagnos/fix the circuit. I breadboard everything now before I stuff a pcb and it pays BIG dividends.Julian <julian at 22host24.com> wrote:
> Oh what an idiot ive been!And so many of you have been so helpful in giving replies, but, stupidly, i was asking the wrong question! (although there is an 4dknocking about here somewhere, which i haven't taken the iron to yet)Its the 4es that i have tried to build. The board is odd, in that there are lots of thru-holes that don't actually go anywhere.Although it is a dual sided board (i haven't filled all the thru holes, as there really isn't, so far as i can tell, any point)I'm sorry for wasting everyone's time on the 4d question - that said however the information kindly given will (in time) still comein useful, but atm, im battling the 4e...So, i guess my original question again - anyone built the 4e successfully?Thanks again, Julian
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