Posts: 90
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Joined: Oct 2011
City: Nipomo
State, Province, Country: CA
Hi all,
I just bought a EICO 330 Signal Generator and will use it to isolate defects in specific stages. It has a coax output cable with alligator clips.
Everything I read, including the EICO manual, stresses that I put a .01 mf cap in the negative lead and a 200 pf cap in series in the hot lead. I don't understand. I can solder a cap on the ground and clip onto it, but how do I put the cap in series in the hot lead and use it to probe?
Alan
Posts: 7,214
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
Hi Alan,
The reason for these two caps is to block any voltage which present in the tested circuit from being applied a cross the output of the generator and to match the impedance of the generator output to the circuit.
If you are working on a set that has a power transformer then you wouldn't necessarily need the cap in the ground leg. If you are using it on a transformerless set you will need it or an isolation transformer.
The cap in the output side could be installed inside the generator where the wire connect internally. You could check the diagram to see if it has a cap in series with the output, don't think two would be necessary. Both of these caps should have a voltage rating of 500v or better, no low voltage stuff here.
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 289
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City: Las Vegas, NV
on the hot lead clip one end of the cap to the alligator clip and use the other lead on the cap as your "probe"
John
Las Vegas, NV USA
Posts: 90
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Joined: Oct 2011
City: Nipomo
State, Province, Country: CA
Thanks guys, I guess I knew what to do, but I feel like I'm guessing until I get the reassurance and support from you. Thanks so, so much for your replies!
Alan
Posts: 2,128
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Joined: Oct 2008
City: Merrick, Long Island, NY
I usually use a coil of about 25 turns of any kind of wire on aTP cardboard and wire it with a .05 cap in series with the signal generator. Good enough coupling for most purposes, but if you want to work backwards from the second IF, etc.. follow alignment instructions. Beware you can be nipped slightly or fatally when working with an old signal generator and old hot chassis radio if you are not careful. Please use an isolation transformer. You can also get an inexpensive new or surplus frequency counter to see where you are from the Eico. Mine is off by a lot, but at least I know how much and in which direction.
