2204 to Dirty Shirley conversion?

  • Thread starter Thread starter ledvedder
  • Start date Start date
My oscilloscope arrived. Why did I assume, since it has a built in signal generator, that it would come with a 1/4" jack?
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ledvedder said:
I ordered a 1/4" to BNC from Amazon. Is it fairly easy to make one from a guitar cable?
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I'd just buy one. My old signal generator has binding posts like some old home stereos and speakers so I used an old cable. And I use it with an old Kenwood oscilloscope but its a rare occasion. I use a computer/software type for work (again, rarely) but have not used it for guitar.
 
glpg80 said:
The internal schematic shows a definite ground to the load as outlined in the 3 prong plugs. You could use 3 to 2 prong adapters on the secondary and it would be fine. Again, this is only to be used when you’re probing with equipment that is wall powered.
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Forgive my ignorance, but wouldn't this essentially be the same as plugging the amp into a non-grounded outlet?
 
ledvedder said:
Forgive my ignorance, but wouldn't this essentially be the same as plugging the amp into a non-grounded outlet?
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No because neutral and ground are tied together in the panel… sometimes. You’re isolating neutral, ground, and hot all three for your own safety when your test equipment is also referenced to neutral and ground.

Here’s a good video as to why it’s for your safety.



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Also let me make it clear that you never want to just plug a device into the wall without a ground reference regardless of whether you’re testing it or not. What that does is make you the reference to ground which can be absolutely deadly. I don’t have to link the countless people dying from touching electrically hot microphones or electrically hot stages but I will if I have to for your safety.

An isolation transformer prevents you from being the return path of a ground loop that involves your DUT and it’s important when using measurement equipment because the probe grounds on an o scope are not isolated and attach to chassis ground directly. So if you touch a ground probe to a ground that isn’t ground, and your DUT isn’t isolated, you very well could be the return path.

The reason it’s not an issue with battery equipment is that they’re floating as they are, so it’s not an issue or a concern for your safety. Additionally, don’t isolate the oscilloscope, always the DUT.
 
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I've traced the signal up to v1b. It's 25v at the grid of v1b, goes to 51v at v1b plate. Then, the v2b grid reads only 1.2v. What could be some causes of this?
 
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Sounds like a voltage divider isn’t voltage dividing - a resistor is open circuit or it could be a cap that’s shorted to ground.
 
I figured it out! Signal wasn't getting to the voltage divider from the 22n cap before v2b. I must've smoked a trace. Ran a jumper wire and all is well! This oscilloscope is the best investment I've made in a long time. Thanks everyone for putting up with all my questions.
 
ledvedder said:
I figured it out! Signal wasn't getting to the voltage divider from the 22n cap before v2b. I must've smoked a trace. Ran a jumper wire and all is well! This oscilloscope is the best investment I've made in a long time. Thanks everyone for putting up with all my questions.
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I have jumper wires on my modded 5150 II. With modding PCB trace type amps, it happens. Glad you could nail it down!
 
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