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When you're looking at the app notes, keep in mind that the transistor is directly driven from ground level, affecting both turn on and off characteristics. A more complicated but much cleaner way is

Hi Charles, The simplest simplification is to view the transistor as a constant resistance in avalanche. It's quite a bit more complicated than that, since you can also view it as a constant voltage

Also, I re-read AN72 (the other Jim Williams fast pulser application note). He put ferrite beads on the avalanche transistor base feed, a 100 ohm series resistor, and only a 5 pf coupling cap, and his

Another look at AN94 shows that the large reverse base current during the avalanche may be important to the drive circuitry. I used a 7404 hex inverter through 10 pf to the base, which has a 12K

Thanks for the tips, Ed. I am always concerned about blowing sampling head diodes, especially since they are a RPITA to replace without OEM parts available. I did successfully replace the diodes in an

Charles wrote: "Not sure where that reflection step in the falling edge is coming from - is that an artifact of the open-end coax charge line? Plenty of (small) ripples too. I have two 100 ohm

Just finished a big photo session allowing us to put up lots of interesting Tek, HP, Fluke and RF gear. Also some nice looking older items in the (ironically new) Antiques section. Some of the RF

Ondrej, Hopefully cleaning and exercise will correct the problem. These switches don't get used that much. I suppose they could wear out, but these are some of the least used switches on the scope. I

It's a brain fart, I have also 2445B 2467B so when I typed 475 I automatically put B there as well. It's regular 475, not even A. I also have 485 to fix and 561A but that's for another day.

Interesting model! Raymond

Thanks Michael, That would explain a lot, I will clean them both thoroughly and I will have a look if I don't have the same configuration brand new ones. I have massive crate full of various

The 10X Mag switch is a multi-contact switch. Look at the Horizontal Amp Schematic in the area of Q1124. It is also possible that the Beam finder switch is intermittent. Both switches can cause

Hi, I have a 475 here with what I thought is just a dirty switch. It's intermittently loosing the horizontal signal, it's triggering fine but the display does not stretch properly or not at all. When

The following photos have been uploaded to the Sampling with 3S2 ( /g/TekScopes/album?id=261250 ) album of the [email protected] group. * 0312211437-00.jpg (

Finally, success with the Jim Williams triggered avalanche pulser design! I even had a 2N2369 in the drawer, a short GR cable with pigtail ends, and a handy 18" piece of RG-58 poly dielectric for a

I have some 1m cables with an SMB female plug on one side and a BNC male plug on the other. I find them more convenient in cramped places like in the DC505. I'm mainly using them on a 7D15 counter.

I think they would work just fine performance-wise, but going direct to BNC will be a bit awkward - try just holding a BNC cable end in front of the DC505 and imagine working it while in place. I'd

agree 100% the Chinese connectors are junk and can damage the instrument. Get a real USA made, search "used" on ebay Jon

If they are SMB they should BUT, repeat BUT at $1.34 each I wouldn’t touch them. Adapters that work properly and don’t inject their own silliness cost money. Save the hassle and buy one from

After searching the archives, I didn’t find the answer to my question. So here it is. I found these on Fleebay. It’s supposedly an SMB to BNC female adaptor. However, they don’t look like