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Test Equipment Anonymous (TEA) group therapy thread

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Vince:

--- Quote from: McBryce on July 05, 2022, 08:13:12 am ---Why are you trying to do this on a phone at all?? I'm sure you have a PC with a speaker, microphone and internet connection. Click the link on a PC and you don't need the phone to be involved at all. For free, without having to register or give credit card details.

McBryce.

--- End quote ---

No there are no mic or camera on my computer, otherwise I would as you say just use that, rather than trying to get it working on a bloody smartphone !  ;)

It's a desktop computer not a modern laptop which have mic and camera as standard since these days laptops are basically closer to a glorified smartphone than an actual computer.

Vince:

--- Quote from: ch_scr on July 05, 2022, 07:13:56 am ---
--- Quote from: Vince on July 04, 2022, 11:52:47 pm ---
So wow... can't believe it, this 2525 is a RACE CAR !!!! 120V/┬Ás 20MHz ?!!  :wtf:

Wow, 120V.... so far all the op-amps I garnered  were at best 20V for the TL054.. and have some that do LESS than one volt IIRC !  :scared:

Can't help, I now feel the urge to wire them up and see that slew rate for myself ! Datasheet specifies what parameters to use to have a chance of getting that...


--- End quote ---
Vince beware! These are uncompensated amplifiers. Which means they are fast, damn fast! But this also means they will oscillate below a certain amplification, usually 5 or so. Have a close look at the datasheet.

[..]

--- End quote ---

Yeah no worries, the datasheet is upfront about that. At the top f the front page they say :

These dielectrically isolated amplifiers are controlled at closed loop gains greater than 3 without external compensation.

and also :

Compensation pin for unity gain capability

So as BD said just put a cap on the compensation input.

To decouple the power pins, the datasheet shows a 1nF cap in  // with a 1uF for the negative rail, and for the positive rail 1nF cap in  // with a 1F cap, which I assume is a typo !  :-DD

That said, seeing the amp oscillate is interesting and educational in itself, then add a compensation cap, starting from a very low value, increasing it progressively to see how it affects the oscillation.
Hiding the ugly stuff is bad, makes the student think / believe that IC's are magical things that "just work" and don't require you to think.  ;D

tggzzz:
Three questions about the components below, on two different test equipment boards:

* what's the "perforated tube" in the centre of both pictures? My guess is an inductor, but why that peculiar construction?
* is there anything interestingly special about the reed relay, Electrol R4174-1
* how long would it take for a ferengi to spot the gold and other components?

Robert763:

--- Quote from: Vince on July 05, 2022, 10:27:34 am ---
--- Quote from: McBryce on July 05, 2022, 08:13:12 am ---Why are you trying to do this on a phone at all?? I'm sure you have a PC with a speaker, microphone and internet connection. Click the link on a PC and you don't need the phone to be involved at all. For free, without having to register or give credit card details.

McBryce.

--- End quote ---

No there are no mic or camera on my computer, otherwise I would as you say just use that, rather than trying to get it working on a bloody smartphone !  ;)

It's a desktop computer not a modern laptop which have mic and camera as standard since these days laptops are basically closer to a glorified smartphone than an actual computer.

--- End quote ---

So go buy a USB camera / Mic or better a USB camera and standard headset with mic and off you go!

Robert763:

--- Quote from: tggzzz on July 05, 2022, 10:59:41 am ---Three questions about the components below, on two different test equipment boards:

* what's the "perforated tube" in the centre of both pictures? My guess is an inductor, but why that peculiar construction?
* is there anything interestingly special about the reed relay, Electrol R4174-1
* how long would it take for a ferengi to spot the gold and other components?
--- End quote ---

I think it is a delay line. It's construction is a bit like a non-inductive power resistor but it's clearly not a power circuit.

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