MSefi.com read only forum (Jan.15,2018)

Input section construction and testing > 50a (Hall/optical circuit) > viii - Talks about leaving C12 open with no jumper. Then it mentions to place a capacitor if there are noise issues with the tach signal:

viii.Leave the C12 location empty - DO NOT jumper it. This is located above "Bowling" in the copyright notice. This capacitor may need to be installed and/or the value increased if there are noise problems with the tach signal - values up to 0.1µF will work. The 0.001µF value is a good starting point.

I wired both the Hall/optical circuits and the VR circuit. Ran the jumpers for the Hall/optical circuit (I am running a GM 8 pin HEI distributor set up on a 4.3l TBI)
I left it open and my tach signal would rapidly jump up and down (within 100 rpms). So I soldered in C12 and there was no difference. I noticed that my tach flucuates causing my ignition advance and dwell to fluctuate.

Here is a video of what I am trying to describe:
https://www.youtube.com/watch?v=ZoW0qQb ... load_owner

1.) The C12 capacitor that I put in was 0.001uF; since this did not seem to have any affect on the flucuation will changing the value of C12 actually help or is it a waste of time?
2.) Is there something else I should be looking for?

Thank you again for your help and appreciate any info. I am not running into too many problems; just looking to move on.

Will

Does anyone know where I would be able to get these different capacitors from?

ironwill11 wrote:Does anyone know where I would be able to get these different capacitors from?

Would help to know where you live. ;-)

In the UK, many of the shops where you could buy just one of this sort of thing have closed down. So you tend to have to use mail order. But such places might well have quite a high minimum order value as they are really for the trade - and such a cap only costs a couple of pennies. Ebay might be the best bet for one, price wise. If you check the BOM in the instructions you'll get the exact spec.

Thanks Dave,

I am in the US, New Jersey. I believe radio shack used to carry stuff like this; however, they went out of business.

I am not an expert on this; however, when I put the C12 capacitor in, it didn't make a difference. So it is kind of hard to believe that this will help. Reading the manual they just give you the maxium uf you can put in the C12 spot. Should I just jump to this maxium?

Will