I am ready for the next step...

[chikov]

Hello everyone,
After working (and playing) with electronics for years. And now, more recently, after building a couple of tube amps (including some from scratch) I am ready to obtain (and learn how to use) the Oscilloscope. I know, that most of you, guys, learned all that in school, but the college where I went, did not teach that... Would any of you be so kind and recommend, first, a book or a website, that teaches the usage of the scope in relation to diagnostics and design of a tube amp? Something that is not written by one engineer for other engineers but by an engineer for intermediate level hobbyists.
Second, what model and brand of oscilloscope would you recommend? Hopefully not very expensive, just to get me started.
Lastly, I understand that I will need a signal generator and a couple of dummy loads... Would you recommend me a good, not too fancy, generator too?
I believe in good quality, expensive equipment, but I do not like to start with fancy stuff. I like to evolve into it.
Thank you,
Alex.

[xtian]

Hi, Alex. You're walking over some well-traveled ground, so I'll try to point to some existing threads.

You can get a used, vintage scope for under $100 on eBay.

Or, Tony offers some advice on cheap, USB, computer-based scopes:

http://diyguitaramps.prophpbb.com/topic52.html

I use this function (signal) generator:

http://www.ebay.com/itm/FG-100-DDS-Func ... 1450609778

You can find them even cheaper with no case, or as a kit.

Dummy loads are easy--just get 25 or 50 watt resistors from Mouser and build your own, 200 watts total is a good load for most amps we tinker with.

Soon, you may find the scope an indispensable tool, and you can invest in a digital model, only $200-300 now.

[martin manning]

My dummy load is here: http://ampgarage.com/forum/viewtopic.ph ... highlight=

There are several inexpensive app's for smart phones that will do for a signal source.

A high-quality vintage Tektronix analog scope can be had for about the same price as an entry-level digital scope. If you get a used scope get one with probes included. A couple of 10x is what you need.

[MakerDP]

Look to Rigol for a cheap, reliable scope that will grow with you and not make you lose some of your initial investment if you upgrade.

As far as a signal generator goes, you really don't need anything except your smartphone and a set of aligator-clip leads. There are fantastic signal generator apps out there for free. Or your PC/Laptop works too since there are websites that also do sig-gen and freeware like Audacity will do some simple sig-gen stuff.

Another thing to consider, if you have a DAW, is to get a signal generator plugin and there are even oscilloscope plugins available, although those are limited in the sense that you can't just probe your audio anywhere in the circuit like you can with a real scope.

I was going to go the USB Scope route until I stared reading horror stories about people frying their PC's and laptops even when they did everything "correctly." So I just bought a Rigol and since I am no engineer, I consider it to be the last scope I will ever need.

[chikov]

Thank you, gentelmen, for all your help.
I like the idea of Rigol scope. Are you talking about something like this:
http://www.ebay.com/itm/RIGOL-DS5022ME- ... SwZVlXvx-R

I will make my own dummy load - that is easy. I will look into iPhone app signal generators - I did not know they exist...

Only one question remains ( and it is most important one for me at this point), which book or website would you recommend that teaches how to use a scope without burning it

[Phil_S]

If it's just for tube amps, no need to go overboard. This should do the job:
http://www.tequipment.net/oscilloscopes ... /?F_Sort=3

[xtian]

This one: https://www.amazon.com/Hantek-DSO5202P- ... B00H1TES4C

I'm a fan.

There was a good thread about o'scope for tube dudes, don't remember where.

[chikov]

Thanks again... I definitely know what I want for Christmas
I have not heard from anyone yet about a book or two ( or an article on the web) that teaches how to use scopes in regard of tube amp diagnostics and adjustments. Is there a source where you, guys, learned it from?

[martin manning]

Specific to your request: https://m.youtube.com/watch?v=xaELqAo4kkQ

BTW, phone signal generators are not very good, but easily good enough for producing a sine wave for audio work.

[xtian]

Ask me if I burned up the headphone amp in my iPhone by trying to inject a sine wave into a high voltage node of an amp.

I did.

Don't be like me. Remember to isolate the device from DC by using a 0.1uF 600v cap between the device and the amp.

[chikov]

Ask me if I burned up the headphone amp in my iPhone by trying to inject a sine wave into a high voltage node of an amp.

I did.

Don't be like me. Remember to isolate the device from DC by using a 0.1uF 600v cap between the device and the amp.

Thank you for the warning - I think I will buy the signal generator off Ebay then.
Colossal, bless his heart, sold me , like new, OWON PDS 50022S digital scope. Christmas is coming early in my house!
I will stop tomorrow at our local Ace Electronics store on Antoine st, here in Houston - see if they have 8 ohm 20-100 watt resistors.
Thank you Martin for the link. I found a couple of more on You tube - good stuff. I checked indexes in several books I have on tube amps - not much about scope usage. Does any one know of a book that talks about it?
I will learn it one way or another, but I am willing to invest in a book too.
Thanks again.

[chikov]

This one: https://www.amazon.com/Hantek-DSO5202P- ... B00H1TES4C

I'm a fan.

There was a good thread about o'scope for tube dudes, don't remember where.

I think I found it:
http://ampgarage.com/forum/viewtopic.ph ... 43&start=0

[MakerDP]

I bought a Rigol DS1054. They might have newer ones in similar price range now.

As far as smartphone sig-gens go... just be "smart" about it. If you are putting your signal into your input jack, which is what you are pretty much going to always be doing, then nothing is going to happen to your phone. There are lots of us out there using our smartphones as sig-gens for our amp builds without any issues. If you are going to patch it into a HV node, well then yeah... *poof* ... all bets are off. Also, there comes a point where square waves tell you much more about what is going on than a sine wave does so you whatever sig-gen you use, make sure it can do square waves too.

There aren't really any books out there about scopes and tube amps. This question comes up quite a bit on forums. The only real comprehensive guide that I've found is this...

http://www.r-type.org/articles/art-125.htm

Pretty short, but there's really not much to it.

[martin manning]

Remember to isolate the device from DC by using a 0.1uF 600v cap between the device and the amp.

I don't think that will be enough to protect the phone. A substantial AC voltage could bass through and inflict harm.

Also, there comes a point where square waves tell you much more about what is going on than a sine wave does so you whatever sig-gen you use, make sure it can do square waves too.

I have not yet found a sig gen app that produces a clean square wave. If you have, which one?

[Gibsonman63]

Chicov, check out Electronic Parts Outlet (EPO) on Fondren. They have used scopes there fairly reasonably and occasionally have workshops where they run through Oscope basics.