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As noted in previous thread, I have been having a problem with vacuum pump and 24" dish clamping jig, and not getting much vacuum pressure. I found a big problem in the parts to pump and the filter connections that I was eventually able to fix.

Now putting finger over the intake nipple (don't know proper terms of these things) with or without hose I now get almost -25lbs of hg and .9 of bar pressure which I know is good. Attaching it to the vacuum clamping jig though, I still only get about -10 lbs of hg and .4 bar. Enough it takes the rubber down and flat onto the dish or bottome of the jig itself and it takes some but little effort to lift lid.

I took the dish out of the jig and placed finger over the hole and nipple that goes into jig and get between -18 and -22 hg and about .7 bar. However, when put the dish back into the clamp jig, I go back to the small amount of hg and bar pressure. I put my finger over notch in dish that allows (or supposed to anyway) the pressure for clamping, I still stay at the noted low pressures.

I need any ideas in how to troubleshoot and find where leak is in the JIG or how to fix this. Note I did put some plastic bag over the notch and that did not allow better pressure. Also the top of jig does not have plexiglass or any other cover over the rubber. I note additionally pressure gauge always shows about -5hg and .2 bar.

Thanks

Small air leaks can be pretty hard to find but it sounds like yours is not small. Sounds like you have the right idea of starting at the source and working your way out, testing along the way.

Often you can hear leaks. If you have enough hose, you could try putting the vacuum pump on the other side of the door to cut down on the other noise.

Water will find larger leaks but not smaller ones.

Maybe a photo of your setup would help.

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Put some dish detergent in the water it will sometimes aid in finding leaks in the conectors and joints. It will bubble up from the air leaks.

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Guitars, guitars and more guitars.

A trick my son taught me for finding small, pesky vacuum leaks is to use a lit incense stick that produces a lot of smoke and slowly pass it around the connections with the vacuum operational. A leak should suck the smoke towards itself. Helps to do this in a calm, breeze free area, but it works!!!

Bingo smoke is the best vacuum leak detector providing you can control the ambient air in the shop. soapy water being drawn into a vacuum leak will not often bubble, but this is a good positive air leak detector. colored or at least smoke with dense particles are helpful to see the current draw.

From your description I suspect some how the dish is causing a miss fit of your seal. Smoke should help you find the issue.

Good tip larry. I have to remember that if I ever have such a problem.

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Guitars, guitars and more guitars.

Thanks have plenty of hose, and will get some incense to give it a try. Love setting up new shop after a couple of years. So many things to find have been messed up in the move and storage. Getting there though.