Q999 155-9999-99 Coherer *Selected by Tek :)

I think this has been previously studied and reported on Tekscopes some years ago. IIRC there are various fluids that will provide the needed dielectric strength, but their dielectric constants made i

Thanks... but don't forget that postage from CA to US is expensive which will tend to offset the savings on a small order. If time is a factor, note that I ordered a part from Walter that was sent out

I've got one of each (7B53 and 7B92 timebases) that need repair and I just don't have the time and inclination to mess with them, and don't think I will any time soon. Way too many projects including

Thank you... that's an good explanation (and picture), and it does make sense. But my faster S-2 with original diodes displays the same behavior in the same setup, although with "only" six or seven st

I also found (in the 3S2 manual) one line that says, "The TRIG OUT signal is not useful for externally triggering a real-time time-base unit". Hmm. But it does not explain *why*. It certainly seems to

Not yet :( As I mentioned in the 3T77A thread, mail from Canada to the US is even slower than usual these days. Still waiting on the hybrid for my S-4 head that Walter sent, too.

I took the S-1 sampling head apart again and discovered one reason it didn't work was that I'd gotten one of the 2N5769 B-E diodes backwards. Turned it around, still very noisy with no input. Decided

Speaking of noise... could you please start new threads for these interesting but unrelated topics? I looked at the 2N3904 and 2N5769 data sheets. They have the same max Ic (200 ma). The 3904 data she

Thanks for all the interesting side discussion... Prof. Lee did answer my question, noting that there would probably be too much blow-by. Too much to be adjusted out by the blow-by compensation circui

Long shot here... does anyone have a case that fits a Tek 114 pulse generator? I got the chassis many years ago with a missing power transformer. Rigged up two transformers (the smaller one is for the

While waiting for my Schottky diodes to repair my S-1 (and possibly my S-2), I did some searching for currently available substitutes. The late, great Bob Pease once wrote: "One "diode" that does turn

The 5.6k (carbon comp) resistor was indeed completely open. It looked perfect, no cracks or swelling, other than some whitish oxidation on the leads. Replaced it with a modern resistor and resumed wor

One step forward, one back. I quickly found that D152 had turned into a resistive lump of silicon (in both directions). Tacked in a 1N4148 and the sweep started up :) I watched the voltage across it d

Having rested and studied the circuit description carefully, it appears that the pulses *should* go away at Q135 because it (and Q145) latch on during each staircase! So Q135 B-E junction is effective

That's an amusing anecdote, but did you have to post it three times in a row? :) Meanwhile, transistor changes didn't help. The staircase never starts (which is what resets the Q135/Q145 latch through

thanks, I was thinking of that (and possibly swapping Q145 for a 2N3904 too?). Hopefully it won't oscillate since those have a 250 MHz Ft, a lot faster than the original Ge device. Could always put fe

I did some more digging in my junkbox and discovered a Tek-numbered bag also labeled "10 ma tunnel diode" :) so I won't have to wait two months for the Russian TDs. It has wire leads (the tiny "top ha

Well crap. Someone beat me to it already, even though I replied minutes after I saw the post :( Whoever you are, how about selling me one of them? thanks.

PM sent! I got a reasonable ebay offer on an S-4 "not working, bad offset" and I figure I can fix anything else except the hybrid. So I guess I'll accept once I confirm with Walter :)