18Watt.com

Here's another interesting bit. In troubleshooting my amp that had a bad OT, I also tried out a Snubber. After replacing the OT, I scoped the power tube grids (no snubber). Take a look:

Then I added the snubber back in, and measured again, everything else the same as the first test:

All the knobs were at 50% for both tests. When they say "smooth out your sound" it looks like it's actually true.

Thanks,
Josh

I figured out a stupid trick that works really well when some caps are harder to tell the difference which side is which...

I turned on a power strip, and kept my bare foot a couple inches from it.

Here's a capacitor without the power strip on: Flipped:
Here's that same capacitor with the power strip on: Flipped:
That silly trick made testing this pile of caps for my upcoming Tremolo TMB build go much faster:
I assume this works because the whole point is for us to be an antenna, and this way the antenna has a stronger signal to work with.

Thanks,
Josh

I see the difference without the power strip. The results look backwards with it on?

crgfrench wrote: ↑

Fri 05/29/20 7:56 pm

I see the difference without the power strip. The results look backwards with it on?

For that cap, yes, it was plenty obvious without the power strip. I'm too lazy to go backwards and retest a cap I already marked.

Good eye. Going back to my laziness, they're out of order because I didn't bother to reconnect the sides in the same order (tested the same side with and without the power strip, then switched). One side is obviously correct, and one isn't.

JMPGuitars wrote: ↑

Wed 09/19/18 9:34 am

Check out this cute adapter:

_JMP3402.jpg

_JMP3400.jpg

Pretty handy when measuring from a parallel output.

Where can I find those? Just ordered the Siglent SDS1052DL+

crgfrench wrote: ↑

Fri 06/12/20 8:28 am

Where can I find those? Just ordered the Siglent SDS1052DL+

These are the ones I have: https://www.amazon.com/gp/product/B06Y1HDSCS

Siglent 1052 nice addition to my bench!

crgfrench wrote: ↑

Mon 06/15/20 10:58 pm

Siglent 1052 nice addition to my bench!

Very nice! Question: why do you still have a bulb tester, if you have a variac?

I use them both for startup, and I made the bulb limiter before I bought the variac. Truly appreciated your earlier advice about the scope, finally decided on 50MHz 2 channel as it's overkill for tube amp building, really 20MHz is more than enough... I do love that web control on yours but I def don't need 4 channels and couldn't justify paying twice as much to get the web control version.

crgfrench wrote: ↑

Tue 06/16/20 1:44 pm

I use them both for startup, and I made the bulb limiter before I bought the variac. Truly appreciated your earlier advice about the scope, finally decided on 50MHz 2 channel as it's overkill for tube amp building, really 20MHz is more than enough... I do love that web control on yours but I def don't need 4 channels and couldn't justify paying twice as much to get the web control version.

No problem. Not that you need it, but I believe there's at least a bandwidth hack for your scope.

I also made a bulb limiter before I got a variac. But it lives in the basement now since it's redundant, and bench real estate is highly competitive.

Wanted to thank all on this thread for sharing the good ideas, especially Josh. The Siglent/Tenma has been working just great for me. Last night calibrated Saul's tube FX loop in this 36W. 1kHz signal, 10V in & 1V buffered.

crgfrench wrote: ↑

Fri 08/14/20 2:17 pm

Wanted to thank all on this thread for sharing the good ideas, especially Josh. The Siglent/Tenma has been working just great for me. Last night calibrated Saul's tube FX loop in this 36W. 1kHz signal, 10V in & 1V buffered.

No problem!

How do you have 10V in? ...and why? Is your friend using active guitars?

Thanks,
Josh

Sorry -- 10V peak to peak, which is 3.5V rms.

crgfrench wrote: ↑

Fri 08/14/20 7:29 pm

Sorry -- 10V peak to peak, which is 3.5V rms.

I had a feeling you meant ptp. That's still pretty high though. Connect your loudest guitar directly to the scope and measure different chords or notes at different attack levels and see what you get.

It is high -- I realized I sent an 800mV signal in instead of a 200mV signal! Now I know exactly what you were talking about with the tenma generator...

crgfrench wrote: ↑

Sat 08/15/20 9:13 am

It is high -- I realized I sent an 800mV signal in instead of a 200mV signal! Now I know exactly what you were talking about with the tenma generator...

On the bright side, you CAN use your scope to dial in the Tenma to the correct mV, but if you ever bump the knob, you gotta set it again. My UTG932E is currently set at exactly 150mV, and won't move if I don't want it to.

Ha, it looks like I just won a new signal generator! I'm getting the SDG2042X, which is awesome. I bought it before and returned it because it was too expensive / more than what I needed...but for free, it's perfect!

So should I sell my UTG932E? Does anybody want it? I paid $130, I suppose I could sell it for $100 plus shipping?

I gotta say though, I really prefer the tiny size of the UTG932E. I'll probably get over it.

Thanks,
Josh

Well, I guess I'm over the AWG size problem... I just received a new scope I also won. lol

This one has a built in AWG, so now I have more bench space again. Yay!

Check it out:
I put velcro on the feet, and a screen protector on the touch screen. I'm sure that will bother somebody somewhere.

As fast as I thought my old scope was, this is much faster/snappier. I'm gonna have some fun with this thing.

Thanks,
Josh

I love my new scope's touch screen. They set it up really well.

Testing for the foil side of a cap:
I'm looking forward to my upcoming build to have some more fun with this scope.

Bought myself a scope too today. Cheap 200$ scope, but it'll have to do for now...
Just learning the basis. Trying to find oscillation in my imperial...

It's a utd2025cl