Bias current, leakage, DC offset? Remote trouble shooting

Why don't you simply use socketed pins what have no body?

There is a procedure for installing them via hand, they sit in a frame while soldering to keep them align then you remove the frame work, leaving nothing but pins with a full support body but no plastic or what ever between the pins.

I am not even sure if you can get those any more? Most likely the reason why many just slot the board and rest the body in the slot while soldering the legs directly to the board.

We have high Z circuit for a photo tube and that is what's done along with a metal cover over the whole thing to keep RF out of it.

Jamie

A R in series with the Cap usually helps that out, we've experienced that before. The cap interacts with the input leads, adding R in series lowers the Q , etc..

Jamie

Yeah, I'm not sure about the bath, so I'm just vague. Some one looked up the recommended mixture for our solder/flux and we use that.

Re IPA: Yeah in this case I think the IPA stopped the breath test because it sucked all the water (along stuff in it.) off the plastic. After the weekend I'll give the IPA washed board another breath test.

George H.

Yeah I didn't know till today that the sockets were a problem. We use to have some good ones! They worked in Singapore with leakage less than a giga ohm. Clearly I'm going to have to find some better sockets, We've got stuff where the socket is needed. (I've been selling them as "a few dollar" input fuse. :^)

There was some other more expensive replacement at Newark, I'll try that first.

I should have some of the old sockets... I've measured ~1 pA of diode leakage current with an opamp in a socket. (there was ~10 pA of "opamp" leakage current that could have been the socket.) I guess I didn't breath on it.

Hey I can make a socket out of FR4, certainly someone will sell me one for less than I can make it.

George H.

Liquid RA flux is the bomb. I use MG 835, which is made just down the street from you, more or less. $26 for a litre on Amazon.

Cheers

Phil Hobbs

Maybe you can just cut away the plastic in situ with a good sharp pair of cutters.

Good to know though.

Thanks, Phil, I'll give it a try. Sayal (local) has lots of 1L and

--sp

Recently I threw out almost all of my solder that wasn't Kester 44 (Sn63Pb37, RA flux). Messing around with RMA for protos is a needless irritation. eBay has it for cheap.

Cheers

Phil Hobbs

This is close to what I was talking about..

They come with carriers, you insert them in the holes, solder and pull the carrier out. This gives you occupied holes with pin sockets with no surrounding material, simply plug the dip into it. They make specific flat pin insertion types. The carrier here is flat so it may accept them from the looks of it.

Jamie

For prototyping I usually pick up a roll or two of 63/37 in China when I'm there- probably similar to what the CM will use anyway. Cheaper than distributors, though the thin stuff (0.015") is still a large premium per pound over the 0.035") stuff. A roll of the thin stuff lasts me almost forever. They also carry lead-free types.. though the most common type is Sn99.3Cu0.7 which isn't quite as nice as some of the more expensive ones.

I came back via UAE (Dubai) a few years ago- took a couple days stopover so had to get a visa and go through their customs (with 100% baggage scan- they also do retina scans on non-Westerners)- they were suspicious of the solder- apparently some folks smuggle gold- and gold looks rather similar to lead-based solder in an X-ray.

--sp

Jamie, Look what I found at digikey. A socket whose body washes away in water.

I can't find any more info on them though... nothing at the onshore tech website.

George H.

And yet it says the MSL is unlimited???

Well that's a new one on me!

Good find...

We had to use a mount frame to keep them aligned, solder and then lift the frame out!.

That looks like it'll come off in the flux bath.!

Jamie

I'm just going to buy a few of everything on DK. So far every 8pin dip socket in my lab dips the keithly 610 down below 1G ohm on the breathe test. I'll post pics of the water double thing, (when ever I get the chance...six other things to do first)

George H.

Just lucky, I've done the pin frame thing, pita and the individual pins are expensive in small quantities.

George H.

You used to be able to get machined pin jacks attached to metal strips. You cut them like breakaway headers, and after soldering the strips came off by bending them a few times. Pretty slick, and maybe worth remembering since the wash-away sockets seem to be going away.

Cheers

Phil Hobbs

Mill-Max - separate pins and sockets. Closed bottom for dip/wave if that's how you roll.

Digikey, Mouser, Newark, Allied have many in stock.

Made my life a lot easier - 48 power opamps on a heatsink aren't the sort of thing you want to be soldering and desoldering a lot.

Oops, a technical error. It was the BNC to banana adapter that was leaking at the ~1G ohm level. All the old Mil-Max sockets that I have seem fine. No signs of leaking with the breath test. All fine to the

George H.