"** So you think having an electro connected across the square generator will have NO effect on the output voltage ?? "
I wrote that wrong.
OK, the 1 KHz square wave I generally get from the probe calibrator but not all of them are compatible. They have to be more than 400 mV and less than 360 ohms source impedance, then I modify it to be 400 mV and 360 ohms souirce impedance.
This is wired directly to the vertical input and set for the top and bottom of the square wave to be equidistant from the center of the screen. The DUT shunts it.
You can tell the differenc between low and high value caps. A 100 uF generally results in a flat line if good. If it has ESR you will see some square wave still. Lower value caps are not as easy to read of course because they give you a quarter sine wave. However, remember you are ooking for the vertical parts of the trace. The fast rise and fall time indicates the ESR.
Try it, and get a bunch of caps and try it with resistors in series with the caps. When there is resistance there is a part of the trace with fast rise/fall times. THAT is excatly what you are looking for.
Another thing to remem,ber is that sme caps are more critical than others. I see where people simply change ALL of them in vintage audio equipment and that is very rarely ever needed. they say it sounds better and I do not disagree, but in most cases they would have gotten the same results by changing maybe a half dozen, rather than fifty of them.
I also got to the point where I didn't pay much attention in TVs anymore. My sister's PC monitor went down with someting like a 1,000 uF at 35 volts. I didn't have ANYTHING at the house at the time aand wanted to just see it work. I put a 100 uF at 160 volts in and it worked. I know that is ridiculous and I told her it is liable to fail soon. But I would get the right cap and put it in. So now I have some stock of caps, or electros as you like to call them and here it is like a YEAR later and that SOB still works.
TV, PC mobos and all that, I determine which caps are all in a bank. Alot of them use four, five, all in parallel. You only need ONE. So I put ONE in for test. Id on't even cut the leads, I reuse the same test caps over and over. If it works and I find out the pamel and the Tcon are good, then I proceed with a repair and change them. but I don''t wate them by changing them all and then have a bunch of caps in the drawer with the leads trimmed, like alot of assholes out there. That costs MONEY, and almost all businesses that are still in buisiness here are wo rkjing on a very small margin. You can't afford to waste parts even if they are only a dollar or two each. Hell, I am to the point of ratyioning solderwick. Seriously, I keep it in a puill bottle so it doesn't dry out and it only comes out when there is money involved.
"Got any idea of the impedance of a 100uF cap at 1kHz ?? "
Ummm, damn I forget so much.
1 / 2 pi F C and then the vector sum of the ESR and ESL I think. Somnething like that. Don't you have the impedance nomograph ?
http://cjh.polyplex.org/electronics/nomograph/
It was gifted by someone on one of the sci.electronics newgroups. I, for one, appreciate it. It will save to your HD but I couldn't get it to run in Firefox right so it is saved in MHT format, which means my copy will only open in IE. You might have different results, or as they say YMMV.
I also started to design a small cap checker based on reading the fast rise and fall times of a square wave. Funny, I recently ran across it, on paper of course. If I design, I do it on paper. I am trying to learn Spice but it is aggravating at times. But seriously, if I ever buoold it it will do what I want. It will read caps both large and small and do it IMMEDIATELY with easily readable display on a simple (multiple for different frequencies) LED bar graph.
However I am not really impelled to finish it. The work I am doing now simply does not require any more advanced solutions than I alreay have. And what's more, that apply the waveform to the DUT thing has even more uses. I was trying to figure out one for inductors but haven't gone that far with that.
Bottom line, it just ain't worth it. I can tell with a scope all I nneed to know.
And BTW, where is Jerry G ? He croak on us or what ? We are in a fifteen year old thread here. Hell, back then we still had Jim Yanik. He is probably pushing up daisys as well. Lenny is still hanging in there. Ho many others are just gone ?
These Googlers who resurrect old threads might be a PITA, but really, now I am reminded of how this group used to be.
Tripped out.