Fender Stage Lead II. Help remembering basics! Lol

[Indyryder02]

I presume you meant 100MHz and not 100Hz. I'm a fan of CRT scopes, unless you spend good money for a high res digital scope.. You can find good quality used analog scopes on eBay for very good prices and I think it's a better value. There are so many great options, so what follows is just my personal experience and not the only good option. I use a Sencore SC61 and have had it for years. It's a great tool. One of the reasons I like it is because there is, aside from the CRT, a digital display that can display DCV, VPP, or FREQ per channel. It saves you having to count squares and hash marks. I'm not trying to sell you on this scope. There are many other good choices.

Edit: Post edited- incorrect link.

Edit (again): Audio frequency range is only up to 20K, so I don't think you need a 100MHz scope for amplifier repair. Also, a dual trace scope is a good thing, but not a necessity.

That looks like a pretty nice scope! Mine is shite! Haha

[Indyryder02]

Yep. That’s encore looks well laid out.. I really kind of like the older more straightforward controls of older scopes. Not having to scroll menus etc. I prefer big knobs and switches that get me where I need to be quickly. But man the se core is a huge beast! Haha I think it’d take up half my bench or I’d have to build it a shelf. I worry I don’t know anything about CRT so would have trouble repairing or maintaining I’d it developed issues… course that’s the same with a new digital one for me. It’d be paper weight if it had some digital issues. I drew the line and digital! Solid state has been tough enough haha.

so seems some key things to look for our sensitivity and low noise floor of course. Tracing sources or noise is one of the hardest things I run into, and I think it’s my lack of quality test instruments. I see some going into the uV’s even down to 1!

I read the teltronix sith 7a22 plug in is great for sub mv level noise tracing.

any others to consider? I’d like to keep it fairly basic and simple to use, not if I’d use many of the newer digital scopes.
man’s size is a factor. Smaller is better for my small workspace of course… but I think a portable one might be too small and again not as straightforward as a bench model.
HP1200 b looks interesting too. Very straightforward, but controls, sensitive to a 100uV. Which is way better than my 5mv I have now. It’s worthless for finding anything really small.
I see some digitals going down to 50uV roo that aren’t priced too bad. Around $400.. but not sure if they’ll have a clean enough resolution and low noise floor needed to utilize that sensitivity.
oh man I want a better scope one way or the other I know that!
mine needs donated to someone learning basics. It’d be find for that.

[Indyryder02]

I’d mentioned a more sensitive scope in another group, and someone mentioned grounding signal at various points (properly)
to locate a low level noise. I know I was helped before with this using a capacitor. ( Forgot the value )
id nuts like a better understanding of this technique. Where I can use it and how to use it safely. And any other techniques for locating the source of low level noises. It’s one of the hardest things I come across to troubleshoot. I’m still getting a better scope either way. Mine is just not very good at all.

thanks in advance for the wisdom!

[Helmholtz]

The principle behind grounding a point in the signal path is "divide and conquer" (or "divide et impera" as the old Romans would have said).
When grounding the input of a stage stops the noise you know that it must come from an earlier stage.

Only points sitting on 0 Vdc may be directly grounded. Otherwise a large value cap is used to short the noise to ground while not interfering with the DC bias.

[Indyryder02]

The principle behind grounding a point in the signal path is "divide and conquer" (or "divide et impera" as the old Romans would have said).
When grounding the input of a stage stops the noise you know that it must come from an earlier stage.

Only points sitting on 0 Vdc may be directly grounded. Otherwise a large value cap is used to short the noise to ground while not interfering with the DC bias.

What value would you recommend? Thanks

[Helmholtz]

With high impedance circuits (e.g. tube amps) 0.1µ should be large enough.
With low impedance SS circuits a larger value like 10µ may be needed to suppress a 60Hz hum.

[g1]

It's also worth noting that the cap & wire used for grounding the signal can act like an antenna and pick up noise/hum, so you may have to pick out the specific noise you are dealing with.

[Helmholtz]

Using short wires and connecting to the nearest ground (to minimize the magnetic loop area) is very unlikely to pick up noticeable noise.
Also avoid touching the cap while testing.